Blame for flink_9/solution/solution.patch

diff --git a/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java b/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java
--- a/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java
+++ b/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java
@@ -18,6 +18,7 @@
 
 package org.apache.flink.api.common.eventtime;
 
+import org.apache.flink.annotation.Internal;
 import org.apache.flink.annotation.Public;
 import org.apache.flink.annotation.VisibleForTesting;
 import org.apache.flink.util.clock.Clock;
@@ -84,7 +85,8 @@ public void onPeriodicEmit(WatermarkOutput output) {
     // ------------------------------------------------------------------------
 
     @VisibleForTesting
-    static final class IdlenessTimer {
+    @Internal
+    public static final class IdlenessTimer {
 
         /** The clock used to measure elapsed time. */
         private final RelativeClock clock;
@@ -104,7 +106,7 @@ static final class IdlenessTimer {
         /** The duration before the output is marked as idle. */
         private final long maxIdleTimeNanos;
 
-        IdlenessTimer(RelativeClock clock, Duration idleTimeout) {
+        public IdlenessTimer(RelativeClock clock, Duration idleTimeout) {
             this.clock = clock;
 
             long idleNanos;
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/EventTimeExtension.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/EventTimeExtension.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/EventTimeExtension.java
@@ -0,0 +1,273 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.api.common.watermark.BoolWatermarkDeclaration;
+import org.apache.flink.api.common.watermark.LongWatermarkDeclaration;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.api.common.watermark.WatermarkDeclarations;
+import org.apache.flink.datastream.api.extension.eventtime.function.EventTimeProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.OneInputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputNonBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoOutputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.strategy.EventTimeExtractor;
+import org.apache.flink.datastream.api.extension.eventtime.strategy.EventTimeWatermarkGeneratorBuilder;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+import org.apache.flink.datastream.api.function.ProcessFunction;
+import org.apache.flink.datastream.api.function.TwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.function.TwoOutputStreamProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/**
+ * The entry point for the event-time extension, which provides the following functionality:
+ *
+ * <ul>
+ *   <li>defines the event-time watermark and idle status watermark. If you use the {@link
+ *       EventTimeWatermarkGeneratorBuilder} below, then you don't need to declare these watermarks
+ *       manually in your application; otherwise you need to declare them in your own {@link
+ *       ProcessFunction}.
+ *   <li>provides the {@link EventTimeWatermarkGeneratorBuilder} to facilitate the generation of
+ *       event time watermarks. An example of using {@link EventTimeWatermarkGeneratorBuilder} is as
+ *       follows:
+ *       <pre>{@code
+ * OneInputStreamProcessFunction<POJO, POJO> watermarkGeneratorProcessFunction
+ *       = EventTimeExtension
+ *       .newWatermarkGeneratorBuilder(POJO::getEventTime)
+ *       .periodicWatermark()
+ *       .buildAsProcessFunction();
+ * source.process(watermarkGeneratorProcessFunction)
+ *       .process(...)
+ * }</pre>
+ *   <li>provides a tool to encapsulate a user-defined {@link EventTimeProcessFunction} to provide
+ *       the relevant components of the event-time extension.
+ *       <pre>{@code
+ * stream.process(
+ *          EventTimeExtension.wrapProcessFunction(
+ *              new CustomEventTimeProcessFunction()
+ *          )
+ *       )
+ *       .process(...)
+ * }</pre>
+ * </ul>
+ */
+@Experimental
+public class EventTimeExtension {
+
+    // =============== Event Time related Watermark Declarations ===============
+
+    /**
+     * Definition of EventTimeWatermark. The EventTimeWatermark represents a specific timestamp,
+     * signifying the passage of time. Once a process function receives an EventTimeWatermark, it
+     * will no longer receive events with a timestamp earlier than that watermark.
+     */
+    public static final LongWatermarkDeclaration EVENT_TIME_WATERMARK_DECLARATION =
+            WatermarkDeclarations.newBuilder("BUILTIN_API_EVENT_TIME")
+                    .typeLong()
+                    .combineFunctionMin()
+                    .combineWaitForAllChannels(true)
+                    .defaultHandlingStrategyForward()
+                    .build();
+
+    /**
+     * Definition of IdleStatusWatermark. The IdleStatusWatermark indicates that a particular input
+     * is in an idle state. When a ProcessFunction receives an IdleStatusWatermark from an input, it
+     * should ignore that input when combining EventTimeWatermarks.
+     */
+    public static final BoolWatermarkDeclaration IDLE_STATUS_WATERMARK_DECLARATION =
+            WatermarkDeclarations.newBuilder("BUILTIN_API_EVENT_TIME_IDLE")
+                    .typeBool()
+                    .combineFunctionAND()
+                    .combineWaitForAllChannels(true)
+                    .defaultHandlingStrategyForward()
+                    .build();
+
+    /**
+     * Determine if the received watermark is an EventTimeWatermark.
+     *
+     * @param watermark The watermark to be checked.
+     * @return true if the watermark is an EventTimeWatermark; false otherwise.
+     */
+    public static boolean isEventTimeWatermark(Watermark watermark) {
+        return isEventTimeWatermark(watermark.getIdentifier());
+    }
+
+    /**
+     * Determine if the received watermark is an EventTimeWatermark by watermark identifier.
+     *
+     * @param watermarkIdentifier The identifier of the watermark to be checked.
+     * @return true if the watermark is an EventTimeWatermark; false otherwise.
+     */
+    public static boolean isEventTimeWatermark(String watermarkIdentifier) {
+        return watermarkIdentifier.equals(EVENT_TIME_WATERMARK_DECLARATION.getIdentifier());
+    }
+
+    /**
+     * Determine if the received watermark is an IdleStatusWatermark.
+     *
+     * @param watermark The watermark to be checked.
+     * @return true if the watermark is an IdleStatusWatermark; false otherwise.
+     */
+    public static boolean isIdleStatusWatermark(Watermark watermark) {
+        return isIdleStatusWatermark(watermark.getIdentifier());
+    }
+
+    /**
+     * Determine if the received watermark is an IdleStatusWatermark by watermark identifier.
+     *
+     * @param watermarkIdentifier The identifier of the watermark to be checked.
+     * @return true if the watermark is an IdleStatusWatermark; false otherwise.
+     */
+    public static boolean isIdleStatusWatermark(String watermarkIdentifier) {
+        return watermarkIdentifier.equals(IDLE_STATUS_WATERMARK_DECLARATION.getIdentifier());
+    }
+
+    // ======== EventTimeWatermarkGeneratorBuilder to generate event time watermarks =========
+
+    /**
+     * Create an instance of {@link EventTimeWatermarkGeneratorBuilder}, which contains a {@code
+     * EventTimeExtractor}.
+     *
+     * @param eventTimeExtractor An instance of {@code EventTimeExtractor} used to extract event
+     *     time information from data records.
+     * @param <T> The type of data records.
+     * @return An instance of {@code EventTimeWatermarkGeneratorBuilder} containing the specified
+     *     event time extractor.
+     */
+    public static <T> EventTimeWatermarkGeneratorBuilder<T> newWatermarkGeneratorBuilder(
+            EventTimeExtractor<T> eventTimeExtractor) {
+        return new EventTimeWatermarkGeneratorBuilder<>(eventTimeExtractor);
+    }
+
+    // ======== Wrap user-defined {@link EventTimeProcessFunction} =========
+
+    /**
+     * Wrap the user-defined {@link OneInputEventTimeStreamProcessFunction}, which will provide
+     * related components such as {@link EventTimeManager} and declare the necessary built-in state
+     * required for the Timer, etc. Note that registering event timers of {@link
+     * EventTimeProcessFunction} can only be used with {@link KeyedPartitionStream}.
+     *
+     * @param processFunction The user-defined {@link OneInputEventTimeStreamProcessFunction} that
+     *     needs to be wrapped.
+     * @return The wrapped {@link OneInputStreamProcessFunction}.
+     */
+    public static <IN, OUT> OneInputStreamProcessFunction<IN, OUT> wrapProcessFunction(
+            OneInputEventTimeStreamProcessFunction<IN, OUT> processFunction) {
+        try {
+            return (OneInputStreamProcessFunction<IN, OUT>)
+                    getEventTimeExtensionImplClass()
+                            .getMethod(
+                                    "wrapProcessFunction",
+                                    OneInputEventTimeStreamProcessFunction.class)
+                            .invoke(null, processFunction);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Wrap the user-defined {@link TwoOutputStreamProcessFunction}, which will provide related
+     * components such as {@link EventTimeManager} and declare the necessary built-in state required
+     * for the Timer, etc. Note that registering event timers of {@link EventTimeProcessFunction}
+     * can only be used with {@link KeyedPartitionStream}.
+     *
+     * @param processFunction The user-defined {@link TwoOutputEventTimeStreamProcessFunction} that
+     *     needs to be wrapped.
+     * @return The wrapped {@link TwoOutputStreamProcessFunction}.
+     */
+    public static <IN, OUT1, OUT2>
+            TwoOutputStreamProcessFunction<IN, OUT1, OUT2> wrapProcessFunction(
+                    TwoOutputEventTimeStreamProcessFunction<IN, OUT1, OUT2> processFunction) {
+        try {
+            return (TwoOutputStreamProcessFunction<IN, OUT1, OUT2>)
+                    getEventTimeExtensionImplClass()
+                            .getMethod(
+                                    "wrapProcessFunction",
+                                    TwoOutputEventTimeStreamProcessFunction.class)
+                            .invoke(null, processFunction);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Wrap the user-defined {@link TwoInputNonBroadcastEventTimeStreamProcessFunction}, which will
+     * provide related components such as {@link EventTimeManager} and declare the necessary
+     * built-in state required for the Timer, etc. Note that registering event timers of {@link
+     * EventTimeProcessFunction} can only be used with {@link KeyedPartitionStream}.
+     *
+     * @param processFunction The user-defined {@link
+     *     TwoInputNonBroadcastEventTimeStreamProcessFunction} that needs to be wrapped.
+     * @return The wrapped {@link TwoInputNonBroadcastStreamProcessFunction}.
+     */
+    public static <IN1, IN2, OUT>
+            TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> wrapProcessFunction(
+                    TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+                            processFunction) {
+        try {
+            return (TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT>)
+                    getEventTimeExtensionImplClass()
+                            .getMethod(
+                                    "wrapProcessFunction",
+                                    TwoInputNonBroadcastEventTimeStreamProcessFunction.class)
+                            .invoke(null, processFunction);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Wrap the user-defined {@link TwoInputBroadcastEventTimeStreamProcessFunction}, which will
+     * provide related components such as {@link EventTimeManager} and declare the necessary
+     * built-in state required for the Timer, etc. Note that registering event timers of {@link
+     * EventTimeProcessFunction} can only be used with {@link KeyedPartitionStream}.
+     *
+     * @param processFunction The user-defined {@link
+     *     TwoInputBroadcastEventTimeStreamProcessFunction} that needs to be wrapped.
+     * @return The wrapped {@link TwoInputBroadcastStreamProcessFunction}.
+     */
+    public static <IN1, IN2, OUT>
+            TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> wrapProcessFunction(
+                    TwoInputBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+                            processFunction) {
+        try {
+            return (TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT>)
+                    getEventTimeExtensionImplClass()
+                            .getMethod(
+                                    "wrapProcessFunction",
+                                    TwoInputBroadcastEventTimeStreamProcessFunction.class)
+                            .invoke(null, processFunction);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /** Get the implementation class of EventTimeExtension. */
+    private static Class<?> getEventTimeExtensionImplClass() {
+        try {
+            return Class.forName(
+                    "org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl");
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException("Please ensure that flink-datastream in your class path");
+        }
+    }
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/EventTimeProcessFunction.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/EventTimeProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/EventTimeProcessFunction.java
@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.function;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.ProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/**
+ * The base interface for event time processing, indicating that the {@link ProcessFunction} will be
+ * enriched with event time processing functions, such as registering event timers and handle event
+ * time watermarks.
+ *
+ * <p>Note that registering event timers can only be used with {@link KeyedPartitionStream}.
+ */
+@Experimental
+public interface EventTimeProcessFunction extends ProcessFunction {
+    /**
+     * Initialize the {@link EventTimeProcessFunction} with an instance of {@link EventTimeManager}.
+     * Note that this method should be invoked before the open method.
+     */
+    void initEventTimeProcessFunction(EventTimeManager eventTimeManager);
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/OneInputEventTimeStreamProcessFunction.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/OneInputEventTimeStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/OneInputEventTimeStreamProcessFunction.java
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.function;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/** The {@link OneInputStreamProcessFunction} that extends with event time support. */
+@Experimental
+public interface OneInputEventTimeStreamProcessFunction<IN, OUT>
+        extends EventTimeProcessFunction, OneInputStreamProcessFunction<IN, OUT> {
+
+    /**
+     * The {@code #onEventTimeWatermark} method signifies that the EventTimeProcessFunction has
+     * received an EventTimeWatermark. Other types of watermarks will be processed by the {@code
+     * ProcessFunction#onWatermark} method.
+     */
+    default void onEventTimeWatermark(
+            long watermarkTimestamp, Collector<OUT> output, NonPartitionedContext<OUT> ctx)
+            throws Exception {}
+
+    /**
+     * Invoked when an event-time timer fires. Note that it is only used in {@link
+     * KeyedPartitionStream}.
+     */
+    default void onEventTimer(long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {}
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputBroadcastEventTimeStreamProcessFunction.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputBroadcastEventTimeStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputBroadcastEventTimeStreamProcessFunction.java
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.function;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.function.TwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/** The {@link TwoInputBroadcastStreamProcessFunction} that extends with event time support. */
+@Experimental
+public interface TwoInputBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+        extends EventTimeProcessFunction, TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> {
+
+    /**
+     * The {@code #onEventTimeWatermark} method signifies that the EventTimeProcessFunction has
+     * received an EventTimeWatermark. Other types of watermarks will be processed by the {@code
+     * ProcessFunction#onWatermark} method.
+     */
+    default void onEventTimeWatermark(
+            long watermarkTimestamp, Collector<OUT> output, NonPartitionedContext<OUT> ctx)
+            throws Exception {}
+
+    /**
+     * Invoked when an event-time timer fires. Note that it is only used in {@link
+     * KeyedPartitionStream}.
+     */
+    default void onEventTimer(long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {}
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputNonBroadcastEventTimeStreamProcessFunction.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputNonBroadcastEventTimeStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoInputNonBroadcastEventTimeStreamProcessFunction.java
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.function;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/** The {@link TwoInputNonBroadcastStreamProcessFunction} that extends with event time support. */
+@Experimental
+public interface TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+        extends EventTimeProcessFunction, TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> {
+
+    /**
+     * The {@code #onEventTimeWatermark} method signifies that the EventTimeProcessFunction has
+     * received an EventTimeWatermark. Other types of watermarks will be processed by the {@code
+     * ProcessFunction#onWatermark} method.
+     */
+    default void onEventTimeWatermark(
+            long watermarkTimestamp, Collector<OUT> output, NonPartitionedContext<OUT> ctx)
+            throws Exception {}
+
+    /**
+     * Invoked when an event-time timer fires. Note that it is only used in {@link
+     * KeyedPartitionStream}.
+     */
+    default void onEventTimer(long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {}
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoOutputEventTimeStreamProcessFunction.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoOutputEventTimeStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/function/TwoOutputEventTimeStreamProcessFunction.java
@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.function;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.TwoOutputNonPartitionedContext;
+import org.apache.flink.datastream.api.context.TwoOutputPartitionedContext;
+import org.apache.flink.datastream.api.function.TwoOutputStreamProcessFunction;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/** The {@link TwoOutputStreamProcessFunction} that extends with event time support. */
+@Experimental
+public interface TwoOutputEventTimeStreamProcessFunction<IN, OUT1, OUT2>
+        extends EventTimeProcessFunction, TwoOutputStreamProcessFunction<IN, OUT1, OUT2> {
+
+    /**
+     * The {@code #onEventTimeWatermark} method signifies that the EventTimeProcessFunction has
+     * received an EventTimeWatermark. Other types of watermarks will be processed by the {@code
+     * ProcessFunction#onWatermark} method.
+     */
+    default void onEventTimeWatermark(
+            long watermarkTimestamp,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputNonPartitionedContext<OUT1, OUT2> ctx)
+            throws Exception {}
+
+    /**
+     * Invoked when an event-time timer fires. Note that it is only used in {@link
+     * KeyedPartitionStream}.
+     */
+    default void onEventTimer(
+            long timestamp,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputPartitionedContext<OUT1, OUT2> ctx) {}
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeExtractor.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeExtractor.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeExtractor.java
@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.strategy;
+
+import org.apache.flink.annotation.Experimental;
+
+import java.io.Serializable;
+
+/** A user function designed to extract event time from an event. */
+@Experimental
+public interface EventTimeExtractor<T> extends Serializable {
+
+    /** Extract the event time from the event, with the result provided in milliseconds. */
+    long extractTimestamp(T event);
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkGeneratorBuilder.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkGeneratorBuilder.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkGeneratorBuilder.java
@@ -0,0 +1,125 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.strategy;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+
+import java.time.Duration;
+
+/**
+ * A utility class for constructing a processing function that extracts event time and generates
+ * event time watermarks in the {@link EventTimeExtension}.
+ */
+@Experimental
+public class EventTimeWatermarkGeneratorBuilder<T> {
+    // how to extract event time from event
+    private EventTimeExtractor<T> eventTimeExtractor;
+
+    // what frequency to generate event time watermark
+    private EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode generateMode =
+            EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PERIODIC;
+
+    // if not set, it will default to the value of the "pipeline.auto-watermark-interval"
+    // configuration.
+    private Duration periodicWatermarkInterval = Duration.ZERO;
+
+    // if set to zero, it will not generate idle status watermark
+    private Duration idleTimeout = Duration.ZERO;
+
+    // max out-of-order time
+    private Duration maxOutOfOrderTime = Duration.ZERO;
+
+    // =========  how to extract event times from events =========
+
+    public EventTimeWatermarkGeneratorBuilder(EventTimeExtractor<T> eventTimeExtractor) {
+        this.eventTimeExtractor = eventTimeExtractor;
+    }
+
+    // =========  generate the event time watermark with what value =========
+
+    public EventTimeWatermarkGeneratorBuilder<T> withIdleness(Duration idleTimeout) {
+        this.idleTimeout = idleTimeout;
+        return this;
+    }
+
+    public EventTimeWatermarkGeneratorBuilder<T> withMaxOutOfOrderTime(Duration maxOutOfOrderTime) {
+        this.maxOutOfOrderTime = maxOutOfOrderTime;
+        return this;
+    }
+
+    // =========  when to generate event time watermark =========
+
+    public EventTimeWatermarkGeneratorBuilder<T> noWatermark() {
+        this.generateMode = EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.NO_WATERMARK;
+        return this;
+    }
+
+    /**
+     * The periodic watermark interval will be set to the value specified by
+     * PipelineOptions#AUTO_WATERMARK_INTERVAL.
+     */
+    public EventTimeWatermarkGeneratorBuilder<T> periodicWatermark() {
+        this.generateMode = EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PERIODIC;
+        return this;
+    }
+
+    public EventTimeWatermarkGeneratorBuilder<T> periodicWatermark(
+            Duration periodicWatermarkInterval) {
+        this.generateMode = EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PERIODIC;
+        this.periodicWatermarkInterval = periodicWatermarkInterval;
+        return this;
+    }
+
+    public EventTimeWatermarkGeneratorBuilder<T> perEventWatermark() {
+        this.generateMode = EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PER_EVENT;
+        return this;
+    }
+
+    // =========  build the watermark generator as process function =========
+
+    public OneInputStreamProcessFunction<T, T> buildAsProcessFunction() {
+        EventTimeWatermarkStrategy<T> watermarkStrategy =
+                new EventTimeWatermarkStrategy<>(
+                        this.eventTimeExtractor,
+                        this.generateMode,
+                        this.periodicWatermarkInterval,
+                        this.idleTimeout,
+                        this.maxOutOfOrderTime);
+
+        try {
+            return (OneInputStreamProcessFunction<T, T>)
+                    getEventTimeExtensionImplClass()
+                            .getMethod("buildAsProcessFunction", EventTimeWatermarkStrategy.class)
+                            .invoke(null, watermarkStrategy);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static Class<?> getEventTimeExtensionImplClass() {
+        try {
+            return Class.forName(
+                    "org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl");
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException("Please ensure that flink-datastream in your class path");
+        }
+    }
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkStrategy.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkStrategy.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkStrategy.java
@@ -0,0 +1,98 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.strategy;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.annotation.Internal;
+
+import java.io.Serializable;
+import java.time.Duration;
+
+/** Component which encapsulates the logic of how and when to extract event time and watermarks. */
+@Experimental
+public class EventTimeWatermarkStrategy<T> implements Serializable {
+    // how to extract event time from event
+    private final EventTimeExtractor<T> eventTimeExtractor;
+
+    // what frequency to generate event time watermark
+    private final EventTimeWatermarkGenerateMode generateMode;
+
+    // if not set, it will default to the value of the "pipeline.auto-watermark-interval"
+    // configuration.
+    private final Duration periodicWatermarkInterval;
+
+    // if set to zero, it will not generate idle status watermark
+    private final Duration idleTimeout;
+
+    // max out-of-order time
+    private final Duration maxOutOfOrderTime;
+
+    public EventTimeWatermarkStrategy(EventTimeExtractor<T> eventTimeExtractor) {
+        this(
+                eventTimeExtractor,
+                EventTimeWatermarkGenerateMode.PERIODIC,
+                Duration.ZERO,
+                Duration.ZERO,
+                Duration.ZERO);
+    }
+
+    public EventTimeWatermarkStrategy(
+            EventTimeExtractor<T> eventTimeExtractor,
+            EventTimeWatermarkGenerateMode generateMode,
+            Duration periodicWatermarkInterval,
+            Duration idleTimeout,
+            Duration maxOutOfOrderTime) {
+        this.eventTimeExtractor = eventTimeExtractor;
+        this.generateMode = generateMode;
+        this.periodicWatermarkInterval = periodicWatermarkInterval;
+        this.idleTimeout = idleTimeout;
+        this.maxOutOfOrderTime = maxOutOfOrderTime;
+    }
+
+    public EventTimeExtractor<T> getEventTimeExtractor() {
+        return eventTimeExtractor;
+    }
+
+    public EventTimeWatermarkGenerateMode getGenerateMode() {
+        return generateMode;
+    }
+
+    public Duration getPeriodicWatermarkInterval() {
+        return periodicWatermarkInterval;
+    }
+
+    public Duration getIdleTimeout() {
+        return idleTimeout;
+    }
+
+    public Duration getMaxOutOfOrderTime() {
+        return maxOutOfOrderTime;
+    }
+
+    /**
+     * {@link EventTimeWatermarkGenerateMode} indicates the frequency at which event-time watermarks
+     * are generated.
+     */
+    @Internal
+    public enum EventTimeWatermarkGenerateMode {
+        NO_WATERMARK,
+        PERIODIC,
+        PER_EVENT,
+    }
+}
diff --git a/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/timer/EventTimeManager.java b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/timer/EventTimeManager.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/timer/EventTimeManager.java
@@ -0,0 +1,53 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.api.extension.eventtime.timer;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.datastream.api.stream.KeyedPartitionStream;
+
+/**
+ * This class is responsible for managing stuff related to event-time/timer. For example, register
+ * and delete event timers, as well as retrieve event time. Note that methods for timer can only be
+ * used in {@link KeyedPartitionStream}.
+ */
+@Experimental
+public interface EventTimeManager {
+    /**
+     * Register an event timer for this process function. The {@code onEventTimer} method will be
+     * invoked when the event time is reached.
+     *
+     * @param timestamp to trigger timer callback.
+     */
+    void registerTimer(long timestamp);
+
+    /**
+     * Deletes the event-time timer with the given trigger timestamp. This method has only an effect
+     * if such a timer was previously registered and did not already expire.
+     *
+     * @param timestamp indicates the timestamp of the timer to delete.
+     */
+    void deleteTimer(long timestamp);
+
+    /**
+     * Get the current event time.
+     *
+     * @return current event time.
+     */
+    long currentTime();
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/EventTimeExtensionImpl.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/EventTimeExtensionImpl.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/EventTimeExtensionImpl.java
@@ -0,0 +1,83 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime;
+
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
+import org.apache.flink.datastream.api.extension.eventtime.function.OneInputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputNonBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoOutputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.strategy.EventTimeWatermarkStrategy;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+import org.apache.flink.datastream.api.function.TwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.api.function.TwoOutputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedOneInputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoOutputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.ExtractEventTimeProcessFunction;
+
+/** The implementation of {@link EventTimeExtension}. */
+public class EventTimeExtensionImpl {
+
+    // ============= Extract Event Time Process Function =============
+
+    /**
+     * Build an {@link ExtractEventTimeProcessFunction} to extract event time according to {@link
+     * EventTimeWatermarkStrategy}.
+     */
+    public static <T> OneInputStreamProcessFunction<T, T> buildAsProcessFunction(
+            EventTimeWatermarkStrategy<T> strategy) {
+        return new ExtractEventTimeProcessFunction<>(strategy);
+    }
+
+    // ============= Wrap Event Time Process Function =============
+
+    public static <IN, OUT> OneInputStreamProcessFunction<IN, OUT> wrapProcessFunction(
+            OneInputEventTimeStreamProcessFunction<IN, OUT> processFunction) {
+        return new EventTimeWrappedOneInputStreamProcessFunction<>(processFunction);
+    }
+
+    public static <IN, OUT1, OUT2>
+            TwoOutputStreamProcessFunction<IN, OUT1, OUT2> wrapProcessFunction(
+                    TwoOutputEventTimeStreamProcessFunction<IN, OUT1, OUT2> processFunction) {
+        return new EventTimeWrappedTwoOutputStreamProcessFunction<>(processFunction);
+    }
+
+    public static <IN1, IN2, OUT>
+            TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> wrapProcessFunction(
+                    TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+                            processFunction) {
+        return new EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction<>(processFunction);
+    }
+
+    public static <IN1, IN2, OUT>
+            TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> wrapProcessFunction(
+                    TwoInputBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+                            processFunction) {
+        return new EventTimeWrappedTwoInputBroadcastStreamProcessFunction<>(processFunction);
+    }
+
+    // ============= Other Utils =============
+    public static boolean isEventTimeExtensionWatermark(Watermark watermark) {
+        return EventTimeExtension.isEventTimeWatermark(watermark)
+                || EventTimeExtension.isIdleStatusWatermark(watermark);
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedOneInputStreamProcessFunction.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedOneInputStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedOneInputStreamProcessFunction.java
@@ -0,0 +1,143 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.functions;
+
+import org.apache.flink.api.common.state.StateDeclaration;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.api.common.watermark.WatermarkHandlingResult;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.extension.eventtime.function.OneInputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.timer.DefaultEventTimeManager;
+import org.apache.flink.runtime.state.VoidNamespace;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.util.Set;
+import java.util.function.Supplier;
+
+/**
+ * The wrapped {@link OneInputEventTimeStreamProcessFunction} that take care of event-time alignment
+ * with idleness.
+ */
+public class EventTimeWrappedOneInputStreamProcessFunction<IN, OUT>
+        implements OneInputStreamProcessFunction<IN, OUT> {
+
+    private final OneInputEventTimeStreamProcessFunction<IN, OUT> wrappedUserFunction;
+
+    private transient EventTimeManager eventTimeManager;
+
+    private transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
+    public EventTimeWrappedOneInputStreamProcessFunction(
+            OneInputEventTimeStreamProcessFunction<IN, OUT> wrappedUserFunction) {
+        this.wrappedUserFunction = Preconditions.checkNotNull(wrappedUserFunction);
+    }
+
+    @Override
+    public void open(NonPartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.initEventTimeProcessFunction(eventTimeManager);
+        wrappedUserFunction.open(ctx);
+    }
+
+    /**
+     * Initialize the event time extension, note that this method should be invoked before open
+     * method.
+     */
+    public void initEventTimeExtension(
+            @Nullable InternalTimerService<VoidNamespace> timerService,
+            Supplier<Long> eventTimeSupplier,
+            EventTimeWatermarkHandler eventTimeWatermarkHandler) {
+        this.eventTimeManager = new DefaultEventTimeManager(timerService, eventTimeSupplier);
+        this.eventTimeWatermarkHandler = eventTimeWatermarkHandler;
+    }
+
+    @Override
+    public void processRecord(IN record, Collector<OUT> output, PartitionedContext<OUT> ctx)
+            throws Exception {
+        wrappedUserFunction.processRecord(record, output, ctx);
+    }
+
+    @Override
+    public void endInput(NonPartitionedContext<OUT> ctx) {
+        wrappedUserFunction.endInput(ctx);
+    }
+
+    @Override
+    public void onProcessingTimer(
+            long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {
+        wrappedUserFunction.onProcessingTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermark(
+            Watermark watermark, Collector<OUT> output, NonPartitionedContext<OUT> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 0);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermark(watermark, output, ctx);
+        }
+    }
+
+    public void onEventTime(long timestamp, Collector<OUT> output, PartitionedContext ctx) {
+        wrappedUserFunction.onEventTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public Set<StateDeclaration> usesStates() {
+        return wrappedUserFunction.usesStates();
+    }
+
+    @Override
+    public Set<? extends WatermarkDeclaration> declareWatermarks() {
+        return wrappedUserFunction.declareWatermarks();
+    }
+
+    @Override
+    public void close() throws Exception {
+        wrappedUserFunction.close();
+    }
+
+    public OneInputStreamProcessFunction<IN, OUT> getWrappedUserFunction() {
+        return wrappedUserFunction;
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputBroadcastStreamProcessFunction.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputBroadcastStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputBroadcastStreamProcessFunction.java
@@ -0,0 +1,180 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.functions;
+
+import org.apache.flink.api.common.state.StateDeclaration;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.api.common.watermark.WatermarkHandlingResult;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.TwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.timer.DefaultEventTimeManager;
+import org.apache.flink.runtime.state.VoidNamespace;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.util.Set;
+import java.util.function.Supplier;
+
+/**
+ * The wrapped {@link TwoInputBroadcastEventTimeStreamProcessFunction} that take care of event-time
+ * alignment with idleness.
+ */
+public class EventTimeWrappedTwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT>
+        implements TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> {
+
+    private final TwoInputBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+            wrappedUserFunction;
+
+    private transient EventTimeManager eventTimeManager;
+
+    private transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
+    public EventTimeWrappedTwoInputBroadcastStreamProcessFunction(
+            TwoInputBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT> wrappedUserFunction) {
+        this.wrappedUserFunction = Preconditions.checkNotNull(wrappedUserFunction);
+    }
+
+    @Override
+    public void open(NonPartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.initEventTimeProcessFunction(eventTimeManager);
+        wrappedUserFunction.open(ctx);
+    }
+
+    /**
+     * Initialize the event time extension, note that this method should be invoked before open
+     * method.
+     */
+    public void initEventTimeExtension(
+            @Nullable InternalTimerService<VoidNamespace> timerService,
+            Supplier<Long> eventTimeSupplier,
+            EventTimeWatermarkHandler eventTimeWatermarkHandler) {
+        this.eventTimeManager = new DefaultEventTimeManager(timerService, eventTimeSupplier);
+        this.eventTimeWatermarkHandler = eventTimeWatermarkHandler;
+    }
+
+    @Override
+    public void processRecordFromNonBroadcastInput(
+            IN1 record, Collector<OUT> output, PartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.processRecordFromNonBroadcastInput(record, output, ctx);
+    }
+
+    @Override
+    public void processRecordFromBroadcastInput(IN2 record, NonPartitionedContext<OUT> ctx)
+            throws Exception {
+        wrappedUserFunction.processRecordFromBroadcastInput(record, ctx);
+    }
+
+    @Override
+    public void endBroadcastInput(NonPartitionedContext<OUT> ctx) {
+        wrappedUserFunction.endBroadcastInput(ctx);
+    }
+
+    @Override
+    public void endNonBroadcastInput(NonPartitionedContext<OUT> ctx) {
+        wrappedUserFunction.endNonBroadcastInput(ctx);
+    }
+
+    @Override
+    public void onProcessingTimer(
+            long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {
+        wrappedUserFunction.onProcessingTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermarkFromBroadcastInput(
+            Watermark watermark, Collector<OUT> output, NonPartitionedContext<OUT> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 0);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermarkFromBroadcastInput(watermark, output, ctx);
+        }
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermarkFromNonBroadcastInput(
+            Watermark watermark, Collector<OUT> output, NonPartitionedContext<OUT> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 1);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermarkFromBroadcastInput(watermark, output, ctx);
+        }
+    }
+
+    public void onEventTime(long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {
+        wrappedUserFunction.onEventTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public void close() throws Exception {
+        wrappedUserFunction.close();
+    }
+
+    @Override
+    public Set<StateDeclaration> usesStates() {
+        return wrappedUserFunction.usesStates();
+    }
+
+    @Override
+    public Set<? extends WatermarkDeclaration> declareWatermarks() {
+        return wrappedUserFunction.declareWatermarks();
+    }
+
+    public TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> getWrappedUserFunction() {
+        return wrappedUserFunction;
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction.java
@@ -0,0 +1,179 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.functions;
+
+import org.apache.flink.api.common.state.StateDeclaration;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.api.common.watermark.WatermarkHandlingResult;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.NonPartitionedContext;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoInputNonBroadcastEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.timer.DefaultEventTimeManager;
+import org.apache.flink.runtime.state.VoidNamespace;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.util.Set;
+import java.util.function.Supplier;
+
+/**
+ * The wrapped {@link TwoInputNonBroadcastEventTimeStreamProcessFunction} that take care of
+ * event-time alignment with idleness.
+ */
+public class EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT>
+        implements TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> {
+
+    private final TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT>
+            wrappedUserFunction;
+
+    private transient EventTimeManager eventTimeManager;
+
+    private transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
+    public EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction(
+            TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1, IN2, OUT> wrappedUserFunction) {
+        this.wrappedUserFunction = Preconditions.checkNotNull(wrappedUserFunction);
+    }
+
+    @Override
+    public void open(NonPartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.initEventTimeProcessFunction(eventTimeManager);
+        wrappedUserFunction.open(ctx);
+    }
+
+    /**
+     * Initialize the event time extension, note that this method should be invoked before open
+     * method.
+     */
+    public void initEventTimeExtension(
+            @Nullable InternalTimerService<VoidNamespace> timerService,
+            Supplier<Long> eventTimeSupplier,
+            EventTimeWatermarkHandler eventTimeWatermarkHandler) {
+        this.eventTimeManager = new DefaultEventTimeManager(timerService, eventTimeSupplier);
+        this.eventTimeWatermarkHandler = eventTimeWatermarkHandler;
+    }
+
+    @Override
+    public void processRecordFromFirstInput(
+            IN1 record, Collector<OUT> output, PartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.processRecordFromFirstInput(record, output, ctx);
+    }
+
+    @Override
+    public void processRecordFromSecondInput(
+            IN2 record, Collector<OUT> output, PartitionedContext<OUT> ctx) throws Exception {
+        wrappedUserFunction.processRecordFromSecondInput(record, output, ctx);
+    }
+
+    @Override
+    public void endFirstInput(NonPartitionedContext<OUT> ctx) {
+        wrappedUserFunction.endFirstInput(ctx);
+    }
+
+    @Override
+    public void endSecondInput(NonPartitionedContext<OUT> ctx) {
+        wrappedUserFunction.endSecondInput(ctx);
+    }
+
+    @Override
+    public void onProcessingTimer(
+            long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {
+        wrappedUserFunction.onProcessingTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermarkFromFirstInput(
+            Watermark watermark, Collector<OUT> output, NonPartitionedContext<OUT> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 0);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermarkFromFirstInput(watermark, output, ctx);
+        }
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermarkFromSecondInput(
+            Watermark watermark, Collector<OUT> output, NonPartitionedContext<OUT> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 1);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermarkFromSecondInput(watermark, output, ctx);
+        }
+    }
+
+    public void onEventTime(long timestamp, Collector<OUT> output, PartitionedContext<OUT> ctx) {
+        wrappedUserFunction.onEventTimer(timestamp, output, ctx);
+    }
+
+    @Override
+    public void close() throws Exception {
+        wrappedUserFunction.close();
+    }
+
+    @Override
+    public Set<StateDeclaration> usesStates() {
+        return wrappedUserFunction.usesStates();
+    }
+
+    @Override
+    public Set<? extends WatermarkDeclaration> declareWatermarks() {
+        return wrappedUserFunction.declareWatermarks();
+    }
+
+    public TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> getWrappedUserFunction() {
+        return wrappedUserFunction;
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoOutputStreamProcessFunction.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoOutputStreamProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/EventTimeWrappedTwoOutputStreamProcessFunction.java
@@ -0,0 +1,156 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.functions;
+
+import org.apache.flink.api.common.state.StateDeclaration;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.api.common.watermark.WatermarkHandlingResult;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.TwoOutputNonPartitionedContext;
+import org.apache.flink.datastream.api.context.TwoOutputPartitionedContext;
+import org.apache.flink.datastream.api.extension.eventtime.function.TwoOutputEventTimeStreamProcessFunction;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.datastream.api.function.TwoOutputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.timer.DefaultEventTimeManager;
+import org.apache.flink.runtime.state.VoidNamespace;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.util.Set;
+import java.util.function.Supplier;
+
+/**
+ * The wrapped {@link TwoOutputEventTimeStreamProcessFunction} that take care of event-time
+ * alignment with idleness.
+ */
+public class EventTimeWrappedTwoOutputStreamProcessFunction<IN, OUT1, OUT2>
+        implements TwoOutputStreamProcessFunction<IN, OUT1, OUT2> {
+
+    private final TwoOutputEventTimeStreamProcessFunction<IN, OUT1, OUT2> wrappedUserFunction;
+
+    private transient EventTimeManager eventTimeManager;
+
+    private transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
+    public EventTimeWrappedTwoOutputStreamProcessFunction(
+            TwoOutputEventTimeStreamProcessFunction<IN, OUT1, OUT2> wrappedUserFunction) {
+        this.wrappedUserFunction = Preconditions.checkNotNull(wrappedUserFunction);
+    }
+
+    @Override
+    public void open(TwoOutputNonPartitionedContext<OUT1, OUT2> ctx) throws Exception {
+        wrappedUserFunction.initEventTimeProcessFunction(eventTimeManager);
+        wrappedUserFunction.open(ctx);
+    }
+
+    /**
+     * Initialize the event time extension, note that this method should be invoked before open
+     * method.
+     */
+    public void initEventTimeExtension(
+            @Nullable InternalTimerService<VoidNamespace> timerService,
+            Supplier<Long> eventTimeSupplier,
+            EventTimeWatermarkHandler eventTimeWatermarkHandler) {
+        this.eventTimeManager = new DefaultEventTimeManager(timerService, eventTimeSupplier);
+        this.eventTimeWatermarkHandler = eventTimeWatermarkHandler;
+    }
+
+    @Override
+    public void processRecord(
+            IN record,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputPartitionedContext<OUT1, OUT2> ctx)
+            throws Exception {
+        wrappedUserFunction.processRecord(record, output1, output2, ctx);
+    }
+
+    @Override
+    public void endInput(TwoOutputNonPartitionedContext<OUT1, OUT2> ctx) {
+        wrappedUserFunction.endInput(ctx);
+    }
+
+    @Override
+    public void onProcessingTimer(
+            long timestamp,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputPartitionedContext<OUT1, OUT2> ctx) {
+        wrappedUserFunction.onProcessingTimer(timestamp, output1, output2, ctx);
+    }
+
+    @Override
+    public WatermarkHandlingResult onWatermark(
+            Watermark watermark,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputNonPartitionedContext<OUT1, OUT2> ctx) {
+        if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark)) {
+            // If the watermark is from the event time extension, process it and call {@code
+            // userFunction#onEventTimeWatermark} when the event time is updated; otherwise, forward
+            // the watermark.
+            try {
+                EventTimeWatermarkHandler.EventTimeUpdateStatus eventTimeUpdateStatus =
+                        eventTimeWatermarkHandler.processWatermark(watermark, 0);
+                if (eventTimeUpdateStatus.isEventTimeUpdated()) {
+                    wrappedUserFunction.onEventTimeWatermark(
+                            eventTimeUpdateStatus.getNewEventTime(), output1, output2, ctx);
+                }
+            } catch (Exception e) {
+                ExceptionUtils.rethrow(e);
+            }
+            // return POLL to indicate that the watermark has been processed
+            return WatermarkHandlingResult.POLL;
+        } else {
+            return wrappedUserFunction.onWatermark(watermark, output1, output2, ctx);
+        }
+    }
+
+    public void onEventTime(
+            long timestamp,
+            Collector<OUT1> output1,
+            Collector<OUT2> output2,
+            TwoOutputPartitionedContext<OUT1, OUT2> ctx) {
+        wrappedUserFunction.onEventTimer(timestamp, output1, output2, ctx);
+    }
+
+    @Override
+    public Set<StateDeclaration> usesStates() {
+        return wrappedUserFunction.usesStates();
+    }
+
+    @Override
+    public Set<? extends WatermarkDeclaration> declareWatermarks() {
+        return wrappedUserFunction.declareWatermarks();
+    }
+
+    @Override
+    public void close() throws Exception {
+        wrappedUserFunction.close();
+    }
+
+    public TwoOutputStreamProcessFunction<IN, OUT1, OUT2> getWrappedUserFunction() {
+        return wrappedUserFunction;
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/ExtractEventTimeProcessFunction.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/ExtractEventTimeProcessFunction.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/functions/ExtractEventTimeProcessFunction.java
@@ -0,0 +1,194 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.functions;
+
+import org.apache.flink.api.common.ExecutionConfig;
+import org.apache.flink.api.common.eventtime.WatermarksWithIdleness.IdlenessTimer;
+import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.api.common.watermark.WatermarkManager;
+import org.apache.flink.configuration.PipelineOptions;
+import org.apache.flink.datastream.api.common.Collector;
+import org.apache.flink.datastream.api.context.PartitionedContext;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
+import org.apache.flink.datastream.api.extension.eventtime.strategy.EventTimeWatermarkStrategy;
+import org.apache.flink.datastream.api.function.OneInputStreamProcessFunction;
+import org.apache.flink.streaming.runtime.tasks.ProcessingTimeService;
+
+import java.io.IOException;
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.apache.flink.util.Preconditions.checkState;
+
+/** A specialized process function designed for extracting event timestamps. */
+public class ExtractEventTimeProcessFunction<IN>
+        implements OneInputStreamProcessFunction<IN, IN>,
+                ProcessingTimeService.ProcessingTimeCallback {
+
+    /** User-defined watermark strategy. */
+    private final EventTimeWatermarkStrategy<IN> watermarkStrategy;
+
+    /** The maximum timestamp encountered so far. */
+    private long currentMaxEventTime = Long.MIN_VALUE;
+
+    private long lastEmittedEventTime = Long.MIN_VALUE;
+
+    /**
+     * The periodic processing timer interval; if not configured by user in {@link
+     * EventTimeWatermarkStrategy}, it will default to the value specified by {@link
+     * PipelineOptions#AUTO_WATERMARK_INTERVAL}.
+     */
+    private long periodicTimerInterval = 0;
+
+    /**
+     * Whether enable create and send {@link EventTimeExtension#IDLE_STATUS_WATERMARK_DECLARATION}.
+     */
+    private boolean enableIdleStatus;
+
+    /** The {@link IdlenessTimer} is utilized to check whether the input is currently idle. */
+    private IdlenessTimer idlenessTimer;
+
+    private boolean isIdleNow = false;
+
+    private final long maxOutOfOrderTimeInMs;
+
+    private ProcessingTimeService processingTimeService;
+
+    private WatermarkManager watermarkManager;
+
+    public ExtractEventTimeProcessFunction(EventTimeWatermarkStrategy<IN> watermarkStrategy) {
+        this.watermarkStrategy = watermarkStrategy;
+        if (watermarkStrategy.getIdleTimeout().toMillis() > 0) {
+            this.enableIdleStatus = true;
+        }
+        this.maxOutOfOrderTimeInMs = watermarkStrategy.getMaxOutOfOrderTime().toMillis();
+    }
+
+    public void initEventTimeExtension(
+            ExecutionConfig config,
+            WatermarkManager watermarkManager,
+            ProcessingTimeService processingTimeService) {
+        this.processingTimeService = processingTimeService;
+        this.watermarkManager = watermarkManager;
+
+        if (enableIdleStatus) {
+            this.idlenessTimer =
+                    new IdlenessTimer(
+                            processingTimeService.getClock(), watermarkStrategy.getIdleTimeout());
+        }
+
+        // May need register timer to check whether the input is idle and periodically send event
+        // time watermarks
+        boolean needRegisterTimer =
+                watermarkStrategy.getGenerateMode()
+                                == EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode
+                                        .PERIODIC
+                        || enableIdleStatus;
+        // set timer interval default to config option {@link
+        // PipelineOptions#AUTO_WATERMARK_INTERVAL}
+        this.periodicTimerInterval = config.getAutoWatermarkInterval();
+        if (watermarkStrategy.getGenerateMode()
+                        == EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PERIODIC
+                && !watermarkStrategy.getPeriodicWatermarkInterval().isZero()) {
+            this.periodicTimerInterval =
+                    watermarkStrategy.getPeriodicWatermarkInterval().toMillis();
+        }
+        checkState(
+                periodicTimerInterval > 0,
+                "Watermark interval " + periodicTimerInterval + " should large to 0.");
+
+        if (needRegisterTimer) {
+            processingTimeService.registerTimer(
+                    processingTimeService.getCurrentProcessingTime() + periodicTimerInterval, this);
+        }
+    }
+
+    @Override
+    public Set<? extends WatermarkDeclaration> declareWatermarks() {
+        // declare EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION
+        // if idle status is enabled, also declare
+        // EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.
+        Set<WatermarkDeclaration> watermarkDeclarations = new HashSet<>();
+        watermarkDeclarations.add(EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION);
+        if (enableIdleStatus) {
+            watermarkDeclarations.add(EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION);
+        }
+        return watermarkDeclarations;
+    }
+
+    @Override
+    public void processRecord(IN record, Collector<IN> output, PartitionedContext<IN> ctx)
+            throws Exception {
+        if (enableIdleStatus) {
+            if (isIdleNow) {
+                watermarkManager.emitWatermark(
+                        EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.newWatermark(false));
+                isIdleNow = false;
+            }
+
+            // mark current input as active
+            idlenessTimer.activity();
+        }
+
+        // extract event time from record
+        long extractedEventTime =
+                watermarkStrategy.getEventTimeExtractor().extractTimestamp(record);
+        currentMaxEventTime = Math.max(currentMaxEventTime, extractedEventTime);
+        output.collectAndOverwriteTimestamp(record, extractedEventTime);
+
+        if (watermarkStrategy.getGenerateMode()
+                == EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PER_EVENT) {
+            // If the per event watermark is utilized, create event time watermark and send
+            tryEmitEventTimeWatermark(ctx.getNonPartitionedContext().getWatermarkManager());
+        }
+    }
+
+    /**
+     * The processing timer has two goals: 1. check whether the input is idle 2. periodically emit
+     * event time watermark
+     */
+    @Override
+    public void onProcessingTime(long time) throws IOException, InterruptedException, Exception {
+        if (enableIdleStatus && idlenessTimer.checkIfIdle()) {
+            if (!isIdleNow) {
+                watermarkManager.emitWatermark(
+                        EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.newWatermark(true));
+                isIdleNow = true;
+            }
+        } else if (watermarkStrategy.getGenerateMode()
+                == EventTimeWatermarkStrategy.EventTimeWatermarkGenerateMode.PERIODIC) {
+            tryEmitEventTimeWatermark(watermarkManager);
+        }
+
+        processingTimeService.registerTimer(time + periodicTimerInterval, this);
+    }
+
+    private void tryEmitEventTimeWatermark(WatermarkManager watermarkManager) {
+        if (currentMaxEventTime == Long.MIN_VALUE) {
+            return;
+        }
+
+        long needEmittedEventTime = currentMaxEventTime - maxOutOfOrderTimeInMs;
+        if (needEmittedEventTime > lastEmittedEventTime) {
+            watermarkManager.emitWatermark(
+                    EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION.newWatermark(
+                            needEmittedEventTime));
+            lastEmittedEventTime = needEmittedEventTime;
+        }
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/timer/DefaultEventTimeManager.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/timer/DefaultEventTimeManager.java
new file mode 100644
--- /dev/null
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/extension/eventtime/timer/DefaultEventTimeManager.java
@@ -0,0 +1,72 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.datastream.impl.extension.eventtime.timer;
+
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
+import org.apache.flink.runtime.state.VoidNamespace;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
+
+import javax.annotation.Nullable;
+
+import java.util.function.Supplier;
+
+/** The implementation of {@link EventTimeManager}. */
+public class DefaultEventTimeManager implements EventTimeManager {
+
+    /**
+     * The timer service of operator, used in register event timer. Note that it cloud be null if
+     * the operator is not a keyed operator.
+     */
+    @Nullable private final InternalTimerService<VoidNamespace> timerService;
+
+    /** The supplier of the current event time. */
+    private final Supplier<Long> eventTimeSupplier;
+
+    public DefaultEventTimeManager(
+            @Nullable InternalTimerService<VoidNamespace> timerService,
+            Supplier<Long> eventTimeSupplier) {
+        this.timerService = timerService;
+        this.eventTimeSupplier = eventTimeSupplier;
+    }
+
+    @Override
+    public void registerTimer(long timestamp) {
+        if (timerService == null) {
+            throw new UnsupportedOperationException(
+                    "Registering event timer is not allowed in NonKeyed Stream.");
+        }
+
+        timerService.registerEventTimeTimer(VoidNamespace.INSTANCE, timestamp);
+    }
+
+    @Override
+    public void deleteTimer(long timestamp) {
+        if (timerService == null) {
+            throw new UnsupportedOperationException(
+                    "Deleting event timer is not allowed in NonKeyed Stream.");
+        }
+
+        timerService.deleteEventTimeTimer(VoidNamespace.INSTANCE, timestamp);
+    }
+
+    @Override
+    public long currentTime() {
+        return eventTimeSupplier.get();
+    }
+}
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedProcessOperator.java
@@ -28,6 +28,7 @@
 import org.apache.flink.datastream.impl.common.TimestampCollector;
 import org.apache.flink.datastream.impl.context.DefaultNonPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedOneInputStreamProcessFunction;
 import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.runtime.state.VoidNamespaceSerializer;
 import org.apache.flink.streaming.api.operators.InternalTimer;
@@ -39,6 +40,7 @@
 
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Supplier;
 
 /** Operator for {@link OneInputStreamProcessFunction} in {@link KeyedPartitionStream}. */
 public class KeyedProcessOperator<KEY, IN, OUT> extends ProcessOperator<IN, OUT>
@@ -84,7 +86,10 @@ protected Object currentKey() {
 
     @Override
     public void onEventTime(InternalTimer<KEY, VoidNamespace> timer) throws Exception {
-        // do nothing at the moment.
+        if (userFunction instanceof EventTimeWrappedOneInputStreamProcessFunction) {
+            ((EventTimeWrappedOneInputStreamProcessFunction<IN, OUT>) userFunction)
+                    .onEventTime(timer.getTimestamp(), getOutputCollector(), partitionedContext);
+        }
     }
 
     @Override
@@ -121,4 +126,14 @@ public void setKeyContextElement1(StreamRecord record) throws Exception {
     public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
+
+    @Override
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return timerService;
+    }
+
+    @Override
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> timerService.currentWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputBroadcastProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputBroadcastProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputBroadcastProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputBroadcastProcessOperator.java
@@ -28,6 +28,7 @@
 import org.apache.flink.datastream.impl.common.TimestampCollector;
 import org.apache.flink.datastream.impl.context.DefaultNonPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputBroadcastStreamProcessFunction;
 import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.runtime.state.VoidNamespaceSerializer;
 import org.apache.flink.streaming.api.operators.InternalTimer;
@@ -39,6 +40,7 @@
 
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Supplier;
 
 /** Operator for {@link TwoInputBroadcastStreamProcessFunction} in {@link KeyedPartitionStream}. */
 public class KeyedTwoInputBroadcastProcessOperator<KEY, IN1, IN2, OUT>
@@ -90,7 +92,10 @@ protected ProcessingTimeManager getProcessingTimeManager() {
 
     @Override
     public void onEventTime(InternalTimer<KEY, VoidNamespace> timer) throws Exception {
-        // do nothing at the moment.
+        if (userFunction instanceof EventTimeWrappedTwoInputBroadcastStreamProcessFunction) {
+            ((EventTimeWrappedTwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT>) userFunction)
+                    .onEventTime(timer.getTimestamp(), getOutputCollector(), partitionedContext);
+        }
     }
 
     @Override
@@ -123,4 +128,14 @@ public void setKeyContextElement1(StreamRecord record) throws Exception {
     public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
+
+    @Override
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return timerService;
+    }
+
+    @Override
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> timerService.currentWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputNonBroadcastProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputNonBroadcastProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputNonBroadcastProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoInputNonBroadcastProcessOperator.java
@@ -28,6 +28,7 @@
 import org.apache.flink.datastream.impl.common.TimestampCollector;
 import org.apache.flink.datastream.impl.context.DefaultNonPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction;
 import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.runtime.state.VoidNamespaceSerializer;
 import org.apache.flink.streaming.api.operators.InternalTimer;
@@ -39,6 +40,7 @@
 
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Supplier;
 
 /**
  * Operator for {@link TwoInputNonBroadcastStreamProcessFunction} in {@link KeyedPartitionStream}.
@@ -92,7 +94,11 @@ protected ProcessingTimeManager getProcessingTimeManager() {
 
     @Override
     public void onEventTime(InternalTimer<KEY, VoidNamespace> timer) throws Exception {
-        // do nothing at the moment.
+        if (userFunction instanceof EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction) {
+            ((EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT>)
+                            userFunction)
+                    .onEventTime(timer.getTimestamp(), getOutputCollector(), partitionedContext);
+        }
     }
 
     @Override
@@ -131,4 +137,14 @@ public void setKeyContextElement2(StreamRecord record) throws Exception {
     public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
+
+    @Override
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return timerService;
+    }
+
+    @Override
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> timerService.currentWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoOutputProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoOutputProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoOutputProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/KeyedTwoOutputProcessOperator.java
@@ -27,6 +27,7 @@
 import org.apache.flink.datastream.impl.common.TimestampCollector;
 import org.apache.flink.datastream.impl.context.DefaultProcessingTimeManager;
 import org.apache.flink.datastream.impl.context.DefaultTwoOutputNonPartitionedContext;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoOutputStreamProcessFunction;
 import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.runtime.state.VoidNamespaceSerializer;
 import org.apache.flink.streaming.api.operators.InternalTimer;
@@ -40,6 +41,7 @@
 
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Supplier;
 
 /** */
 public class KeyedTwoOutputProcessOperator<KEY, IN, OUT_MAIN, OUT_SIDE>
@@ -113,7 +115,14 @@ protected ProcessingTimeManager getProcessingTimeManager() {
 
     @Override
     public void onEventTime(InternalTimer<KEY, VoidNamespace> timer) throws Exception {
-        // do nothing at the moment.
+        if (userFunction instanceof EventTimeWrappedTwoOutputStreamProcessFunction) {
+            ((EventTimeWrappedTwoOutputStreamProcessFunction<IN, OUT_MAIN, OUT_SIDE>) userFunction)
+                    .onEventTime(
+                            timer.getTimestamp(),
+                            getMainCollector(),
+                            getSideCollector(),
+                            partitionedContext);
+        }
     }
 
     @Override
@@ -146,4 +155,14 @@ public void setKeyContextElement1(StreamRecord record) throws Exception {
     public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
+
+    @Override
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return timerService;
+    }
+
+    @Override
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> timerService.currentWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/ProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/ProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/ProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/ProcessOperator.java
@@ -30,17 +30,24 @@
 import org.apache.flink.datastream.impl.context.DefaultPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultRuntimeContext;
 import org.apache.flink.datastream.impl.context.UnsupportedProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedOneInputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.ExtractEventTimeProcessFunction;
 import org.apache.flink.runtime.asyncprocessing.operators.AbstractAsyncStateUdfStreamOperator;
 import org.apache.flink.runtime.event.WatermarkEvent;
+import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.streaming.api.operators.BoundedOneInput;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
 import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
 import org.apache.flink.streaming.api.operators.StreamingRuntimeContext;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
 
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 /** Operator for {@link OneInputStreamProcessFunction}. */
@@ -59,6 +66,9 @@ public class ProcessOperator<IN, OUT>
     protected transient Map<String, AbstractInternalWatermarkDeclaration<?>>
             watermarkDeclarationMap;
 
+    // {@link EventTimeWatermarkHandler} will be used to process event time related watermarks
+    protected transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
     public ProcessOperator(OneInputStreamProcessFunction<IN, OUT> userFunction) {
         super(userFunction);
     }
@@ -98,6 +108,24 @@ public void open() throws Exception {
         outputCollector = getOutputCollector();
         nonPartitionedContext = getNonPartitionedContext();
         partitionedContext.setNonPartitionedContext(nonPartitionedContext);
+        this.eventTimeWatermarkHandler =
+                new EventTimeWatermarkHandler(1, output, timeServiceManager);
+
+        // Initialize event time extension related ProcessFunction
+        if (userFunction instanceof ExtractEventTimeProcessFunction) {
+            ((ExtractEventTimeProcessFunction<IN>) userFunction)
+                    .initEventTimeExtension(
+                            getExecutionConfig(),
+                            partitionedContext.getNonPartitionedContext().getWatermarkManager(),
+                            getProcessingTimeService());
+        } else if (userFunction instanceof EventTimeWrappedOneInputStreamProcessFunction) {
+            // note that the {@code initEventTimeExtension} in EventTimeWrappedProcessFunction
+            // should be invoked before the {@code open}.
+            ((EventTimeWrappedOneInputStreamProcessFunction<IN, OUT>) userFunction)
+                    .initEventTimeExtension(
+                            getTimerService(), getEventTimeSupplier(), eventTimeWatermarkHandler);
+        }
+
         userFunction.open(nonPartitionedContext);
     }
 
@@ -117,7 +145,14 @@ public void processWatermarkInternal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 0);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -140,6 +175,7 @@ protected BiConsumer<Runnable, Object> getProcessorWithKey() {
         } else {
             return (r, k) -> {
                 Object oldKey = currentKey();
+                setCurrentKey(k);
                 try {
                     r.run();
                 } finally {
@@ -175,4 +211,12 @@ public boolean isAsyncStateProcessingEnabled() {
         // For non-keyed operators, we disable async state processing.
         return false;
     }
+
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return null;
+    }
+
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> eventTimeWatermarkHandler.getLastEmitWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputBroadcastProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputBroadcastProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputBroadcastProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputBroadcastProcessOperator.java
@@ -30,17 +30,23 @@
 import org.apache.flink.datastream.impl.context.DefaultPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultRuntimeContext;
 import org.apache.flink.datastream.impl.context.UnsupportedProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputBroadcastStreamProcessFunction;
 import org.apache.flink.runtime.asyncprocessing.operators.AbstractAsyncStateUdfStreamOperator;
 import org.apache.flink.runtime.event.WatermarkEvent;
+import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.streaming.api.operators.BoundedMultiInput;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
 import org.apache.flink.streaming.api.operators.StreamingRuntimeContext;
 import org.apache.flink.streaming.api.operators.TwoInputStreamOperator;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
 
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 import static org.apache.flink.util.Preconditions.checkState;
@@ -62,6 +68,9 @@ public class TwoInputBroadcastProcessOperator<IN1, IN2, OUT>
     protected transient Map<String, AbstractInternalWatermarkDeclaration<?>>
             watermarkDeclarationMap;
 
+    // {@link EventTimeWatermarkHandler} will be used to process event time related watermarks
+    protected transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
     public TwoInputBroadcastProcessOperator(
             TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> userFunction) {
         super(userFunction);
@@ -100,6 +109,17 @@ public void open() throws Exception {
                         getOperatorStateBackend());
         this.nonPartitionedContext = getNonPartitionedContext();
         this.partitionedContext.setNonPartitionedContext(this.nonPartitionedContext);
+        this.eventTimeWatermarkHandler =
+                new EventTimeWatermarkHandler(2, output, timeServiceManager);
+
+        if (userFunction instanceof EventTimeWrappedTwoInputBroadcastStreamProcessFunction) {
+            // note that the {@code initEventTimeExtension} in EventTimeWrappedProcessFunction
+            // should be invoked before the {@code open}.
+            ((EventTimeWrappedTwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT>) userFunction)
+                    .initEventTimeExtension(
+                            getTimerService(), getEventTimeSupplier(), eventTimeWatermarkHandler);
+        }
+
         this.userFunction.open(this.nonPartitionedContext);
     }
 
@@ -126,7 +146,13 @@ public void processWatermark1Internal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 0);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -140,7 +166,13 @@ public void processWatermark2Internal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 1);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -204,4 +236,12 @@ public boolean isAsyncStateProcessingEnabled() {
         // For non-keyed operators, we disable async state processing.
         return false;
     }
+
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return null;
+    }
+
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> eventTimeWatermarkHandler.getLastEmitWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputNonBroadcastProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputNonBroadcastProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputNonBroadcastProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoInputNonBroadcastProcessOperator.java
@@ -23,25 +23,33 @@
 import org.apache.flink.api.common.watermark.WatermarkHandlingStrategy;
 import org.apache.flink.datastream.api.context.NonPartitionedContext;
 import org.apache.flink.datastream.api.context.ProcessingTimeManager;
+import org.apache.flink.datastream.api.extension.eventtime.timer.EventTimeManager;
 import org.apache.flink.datastream.api.function.TwoInputNonBroadcastStreamProcessFunction;
 import org.apache.flink.datastream.impl.common.OutputCollector;
 import org.apache.flink.datastream.impl.common.TimestampCollector;
 import org.apache.flink.datastream.impl.context.DefaultNonPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultRuntimeContext;
 import org.apache.flink.datastream.impl.context.UnsupportedProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.timer.DefaultEventTimeManager;
 import org.apache.flink.runtime.asyncprocessing.operators.AbstractAsyncStateUdfStreamOperator;
 import org.apache.flink.runtime.event.WatermarkEvent;
 import org.apache.flink.runtime.state.OperatorStateBackend;
+import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.streaming.api.operators.BoundedMultiInput;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
 import org.apache.flink.streaming.api.operators.StreamingRuntimeContext;
 import org.apache.flink.streaming.api.operators.TwoInputStreamOperator;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
 
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 import static org.apache.flink.util.Preconditions.checkState;
@@ -63,6 +71,9 @@ public class TwoInputNonBroadcastProcessOperator<IN1, IN2, OUT>
     protected transient Map<String, AbstractInternalWatermarkDeclaration<?>>
             watermarkDeclarationMap;
 
+    // {@link EventTimeWatermarkHandler} will be used to process event time related watermarks
+    protected transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
     public TwoInputNonBroadcastProcessOperator(
             TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> userFunction) {
         super(userFunction);
@@ -103,6 +114,20 @@ public void open() throws Exception {
                         operatorStateBackend);
         this.nonPartitionedContext = getNonPartitionedContext();
         this.partitionedContext.setNonPartitionedContext(this.nonPartitionedContext);
+        this.eventTimeWatermarkHandler =
+                new EventTimeWatermarkHandler(2, output, timeServiceManager);
+
+        if (userFunction instanceof EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction) {
+            // note that the {@code initEventTimeExtension} in EventTimeWrappedProcessFunction
+            // should be invoked before the {@code open}.
+            EventTimeManager eventTimeManager =
+                    new DefaultEventTimeManager(getTimerService(), getEventTimeSupplier());
+            ((EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT>)
+                            userFunction)
+                    .initEventTimeExtension(
+                            getTimerService(), getEventTimeSupplier(), eventTimeWatermarkHandler);
+        }
+
         this.userFunction.open(this.nonPartitionedContext);
     }
 
@@ -129,7 +154,13 @@ public void processWatermark1Internal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 0);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -143,7 +174,13 @@ public void processWatermark2Internal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 1);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -207,4 +244,12 @@ public boolean isAsyncStateProcessingEnabled() {
         // For non-keyed operators, we disable async state processing.
         return false;
     }
+
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return null;
+    }
+
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> eventTimeWatermarkHandler.getLastEmitWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoOutputProcessOperator.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoOutputProcessOperator.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoOutputProcessOperator.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/operators/TwoOutputProcessOperator.java
@@ -31,19 +31,25 @@
 import org.apache.flink.datastream.impl.context.DefaultTwoOutputNonPartitionedContext;
 import org.apache.flink.datastream.impl.context.DefaultTwoOutputPartitionedContext;
 import org.apache.flink.datastream.impl.context.UnsupportedProcessingTimeManager;
+import org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoOutputStreamProcessFunction;
 import org.apache.flink.runtime.asyncprocessing.operators.AbstractAsyncStateUdfStreamOperator;
 import org.apache.flink.runtime.event.WatermarkEvent;
+import org.apache.flink.runtime.state.VoidNamespace;
 import org.apache.flink.streaming.api.operators.BoundedOneInput;
+import org.apache.flink.streaming.api.operators.InternalTimerService;
 import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
 import org.apache.flink.streaming.api.operators.Output;
 import org.apache.flink.streaming.api.operators.StreamingRuntimeContext;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkHandler;
 import org.apache.flink.util.OutputTag;
 
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 /**
@@ -70,6 +76,9 @@ public class TwoOutputProcessOperator<IN, OUT_MAIN, OUT_SIDE>
     protected transient Map<String, AbstractInternalWatermarkDeclaration<?>>
             watermarkDeclarationMap;
 
+    // {@link EventTimeWatermarkHandler} will be used to process event time related watermarks
+    protected transient EventTimeWatermarkHandler eventTimeWatermarkHandler;
+
     public TwoOutputProcessOperator(
             TwoOutputStreamProcessFunction<IN, OUT_MAIN, OUT_SIDE> userFunction,
             OutputTag<OUT_SIDE> outputTag) {
@@ -112,6 +121,16 @@ public void open() throws Exception {
                         operatorStateStore);
         this.nonPartitionedContext = getNonPartitionedContext();
         this.partitionedContext.setNonPartitionedContext(nonPartitionedContext);
+        this.eventTimeWatermarkHandler =
+                new EventTimeWatermarkHandler(1, output, timeServiceManager);
+        if (userFunction instanceof EventTimeWrappedTwoOutputStreamProcessFunction) {
+            // note that the {@code initEventTimeExtension} in EventTimeWrappedProcessFunction
+            // should be invoked before the {@code open}.
+            ((EventTimeWrappedTwoOutputStreamProcessFunction<IN, OUT_MAIN, OUT_SIDE>) userFunction)
+                    .initEventTimeExtension(
+                            getTimerService(), getEventTimeSupplier(), eventTimeWatermarkHandler);
+        }
+
         this.userFunction.open(this.nonPartitionedContext);
     }
 
@@ -136,7 +155,13 @@ public void processWatermarkInternal(WatermarkEvent watermark) throws Exception
                                 .get(watermark.getWatermark().getIdentifier())
                                 .getDefaultHandlingStrategy()
                         == WatermarkHandlingStrategy.FORWARD) {
-            output.emitWatermark(watermark);
+            if (EventTimeExtensionImpl.isEventTimeExtensionWatermark(watermark.getWatermark())) {
+                // if the watermark is event time related watermark, process them to advance event
+                // time
+                eventTimeWatermarkHandler.processWatermark(watermark.getWatermark(), 0);
+            } else {
+                output.emitWatermark(watermark);
+            }
         }
     }
 
@@ -222,4 +247,12 @@ public boolean isAsyncStateProcessingEnabled() {
         // For non-keyed operators, we disable async state processing.
         return false;
     }
+
+    protected InternalTimerService<VoidNamespace> getTimerService() {
+        return null;
+    }
+
+    protected Supplier<Long> getEventTimeSupplier() {
+        return () -> eventTimeWatermarkHandler.getLastEmitWatermark();
+    }
 }
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/BroadcastStreamImpl.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/BroadcastStreamImpl.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/BroadcastStreamImpl.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/BroadcastStreamImpl.java
@@ -63,6 +63,11 @@ public <K, T_OTHER, OUT> ProcessConfigurableAndNonKeyedPartitionStream<OUT> conn
         // no state redistribution mode check is required here, since all redistribution modes are
         // acceptable
 
+        other =
+                other instanceof ProcessConfigurableAndKeyedPartitionStreamImpl
+                        ? ((ProcessConfigurableAndKeyedPartitionStreamImpl) other)
+                                .getKeyedPartitionStream()
+                        : other;
         TypeInformation<OUT> outTypeInfo =
                 StreamUtils.getOutputTypeForTwoInputBroadcastProcessFunction(
                         processFunction,
@@ -92,6 +97,11 @@ public <T_OTHER, OUT> ProcessConfigurableAndNonKeyedPartitionStream<OUT> connect
                 processFunction.usesStates(),
                 new HashSet<>(Collections.singletonList(StateDeclaration.RedistributionMode.NONE)));
 
+        other =
+                other instanceof ProcessConfigurableAndNonKeyedPartitionStreamImpl
+                        ? ((ProcessConfigurableAndNonKeyedPartitionStreamImpl) other)
+                                .getNonKeyedPartitionStream()
+                        : other;
         TypeInformation<OUT> outTypeInfo =
                 StreamUtils.getOutputTypeForTwoInputBroadcastProcessFunction(
                         processFunction,
@@ -118,6 +128,11 @@ public <K, T_OTHER, OUT> ProcessConfigurableAndKeyedPartitionStream<K, OUT> conn
             KeyedPartitionStream<K, T_OTHER> other,
             TwoInputBroadcastStreamProcessFunction<T_OTHER, T, OUT> processFunction,
             KeySelector<OUT, K> newKeySelector) {
+        other =
+                other instanceof ProcessConfigurableAndKeyedPartitionStreamImpl
+                        ? ((ProcessConfigurableAndKeyedPartitionStreamImpl) other)
+                                .getKeyedPartitionStream()
+                        : other;
         TypeInformation<OUT> outTypeInfo =
                 StreamUtils.getOutputTypeForTwoInputBroadcastProcessFunction(
                         processFunction,
diff --git a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/utils/StreamUtils.java b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/utils/StreamUtils.java
--- a/flink-datastream/src/main/java/org/apache/flink/datastream/impl/utils/StreamUtils.java
+++ b/flink-datastream/src/main/java/org/apache/flink/datastream/impl/utils/StreamUtils.java
@@ -34,6 +34,10 @@
 import org.apache.flink.datastream.api.stream.GlobalStream.ProcessConfigurableAndGlobalStream;
 import org.apache.flink.datastream.api.stream.KeyedPartitionStream.ProcessConfigurableAndKeyedPartitionStream;
 import org.apache.flink.datastream.api.stream.NonKeyedPartitionStream.ProcessConfigurableAndNonKeyedPartitionStream;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedOneInputStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction;
+import org.apache.flink.datastream.impl.extension.eventtime.functions.EventTimeWrappedTwoOutputStreamProcessFunction;
 import org.apache.flink.datastream.impl.extension.join.operators.TwoInputNonBroadcastJoinProcessFunction;
 import org.apache.flink.datastream.impl.stream.AbstractDataStream;
 import org.apache.flink.datastream.impl.stream.GlobalStreamImpl;
@@ -66,6 +70,12 @@ public final class StreamUtils {
     public static <IN, OUT> TypeInformation<OUT> getOutputTypeForOneInputProcessFunction(
             OneInputStreamProcessFunction<IN, OUT> processFunction,
             TypeInformation<IN> inTypeInformation) {
+        if (processFunction instanceof EventTimeWrappedOneInputStreamProcessFunction) {
+            processFunction =
+                    ((EventTimeWrappedOneInputStreamProcessFunction) processFunction)
+                            .getWrappedUserFunction();
+        }
+
         return TypeExtractor.getUnaryOperatorReturnType(
                 processFunction,
                 OneInputStreamProcessFunction.class,
@@ -101,6 +111,12 @@ TypeInformation<OUT> getOutputTypeForTwoInputNonBroadcastProcessFunction(
                     true);
         }
 
+        if (processFunction instanceof EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction) {
+            processFunction =
+                    ((EventTimeWrappedTwoInputNonBroadcastStreamProcessFunction) processFunction)
+                            .getWrappedUserFunction();
+        }
+
         return TypeExtractor.getBinaryOperatorReturnType(
                 processFunction,
                 TwoInputNonBroadcastStreamProcessFunction.class,
@@ -123,6 +139,12 @@ TypeInformation<OUT> getOutputTypeForTwoInputBroadcastProcessFunction(
                     TwoInputBroadcastStreamProcessFunction<IN1, IN2, OUT> processFunction,
                     TypeInformation<IN1> in1TypeInformation,
                     TypeInformation<IN2> in2TypeInformation) {
+        if (processFunction instanceof EventTimeWrappedTwoInputBroadcastStreamProcessFunction) {
+            processFunction =
+                    ((EventTimeWrappedTwoInputBroadcastStreamProcessFunction) processFunction)
+                            .getWrappedUserFunction();
+        }
+
         return TypeExtractor.getBinaryOperatorReturnType(
                 processFunction,
                 TwoInputBroadcastStreamProcessFunction.class,
@@ -146,6 +168,15 @@ TypeInformation<OUT> getOutputTypeForTwoInputBroadcastProcessFunction(
                             TwoOutputStreamProcessFunction<IN, OUT1, OUT2>
                                     twoOutputStreamProcessFunction,
                             TypeInformation<IN> inTypeInformation) {
+
+        if (twoOutputStreamProcessFunction
+                instanceof EventTimeWrappedTwoOutputStreamProcessFunction) {
+            twoOutputStreamProcessFunction =
+                    ((EventTimeWrappedTwoOutputStreamProcessFunction)
+                                    twoOutputStreamProcessFunction)
+                            .getWrappedUserFunction();
+        }
+
         TypeInformation<OUT1> firstOutputType =
                 TypeExtractor.getUnaryOperatorReturnType(
                         twoOutputStreamProcessFunction,
diff --git a/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/io/AbstractStreamTaskNetworkInput.java b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/io/AbstractStreamTaskNetworkInput.java
--- a/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/io/AbstractStreamTaskNetworkInput.java
+++ b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/io/AbstractStreamTaskNetworkInput.java
@@ -36,6 +36,7 @@
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
 import org.apache.flink.streaming.runtime.watermark.WatermarkCombiner;
 import org.apache.flink.streaming.runtime.watermarkstatus.StatusWatermarkValve;
+import org.apache.flink.streaming.util.watermark.WatermarkUtils;
 import org.apache.flink.util.ExceptionUtils;
 
 import java.io.IOException;
@@ -118,8 +119,14 @@ public AbstractStreamTaskNetworkInput(
         this.recordAttributesCombiner =
                 new RecordAttributesCombiner(checkpointedInputGate.getNumberOfInputChannels());
 
+        WatermarkUtils.addEventTimeWatermarkCombinerIfNeeded(
+                watermarkDeclarationSet, watermarkCombiners, flattenedChannelIndices.size());
         for (AbstractInternalWatermarkDeclaration<?> watermarkDeclaration :
                 watermarkDeclarationSet) {
+            if (watermarkCombiners.containsKey(watermarkDeclaration.getIdentifier())) {
+                continue;
+            }
+
             watermarkCombiners.put(
                     watermarkDeclaration.getIdentifier(),
                     watermarkDeclaration.createWatermarkCombiner(
diff --git a/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkCombiner.java b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkCombiner.java
new file mode 100644
--- /dev/null
+++ b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkCombiner.java
@@ -0,0 +1,117 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.runtime.watermark.extension.eventtime;
+
+import org.apache.flink.api.common.watermark.BoolWatermark;
+import org.apache.flink.api.common.watermark.LongWatermark;
+import org.apache.flink.api.common.watermark.Watermark;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
+import org.apache.flink.runtime.event.WatermarkEvent;
+import org.apache.flink.streaming.runtime.io.PushingAsyncDataInput.DataOutput;
+import org.apache.flink.streaming.runtime.streamrecord.LatencyMarker;
+import org.apache.flink.streaming.runtime.streamrecord.RecordAttributes;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.streaming.runtime.watermark.WatermarkCombiner;
+import org.apache.flink.streaming.runtime.watermarkstatus.StatusWatermarkValve;
+import org.apache.flink.streaming.runtime.watermarkstatus.WatermarkStatus;
+
+import java.util.function.Consumer;
+
+/**
+ * A {@link WatermarkCombiner} used to combine {@link EventTimeExtension} related watermarks in
+ * input channels.
+ */
+public class EventTimeWatermarkCombiner extends StatusWatermarkValve implements WatermarkCombiner {
+
+    private WrappedDataOutput<?> output;
+
+    public EventTimeWatermarkCombiner(int numInputChannels) {
+        super(numInputChannels);
+        this.output = new WrappedDataOutput<>();
+    }
+
+    @Override
+    public void combineWatermark(
+            Watermark watermark, int channelIndex, Consumer<Watermark> watermarkEmitter)
+            throws Exception {
+        output.setWatermarkEmitter(watermarkEmitter);
+
+        if (EventTimeExtension.isEventTimeWatermark(watermark)) {
+            inputWatermark(
+                    new org.apache.flink.streaming.api.watermark.Watermark(
+                            ((LongWatermark) watermark).getValue()),
+                    channelIndex,
+                    output);
+        } else if (EventTimeExtension.isIdleStatusWatermark(watermark.getIdentifier())) {
+            inputWatermarkStatus(
+                    new WatermarkStatus(
+                            ((BoolWatermark) watermark).getValue()
+                                    ? WatermarkStatus.IDLE_STATUS
+                                    : WatermarkStatus.ACTIVE_STATUS),
+                    channelIndex,
+                    output);
+        }
+    }
+
+    /** Wrap {@link DataOutput} to emit watermarks using {@code watermarkEmitter}. */
+    static class WrappedDataOutput<T> implements DataOutput<T> {
+
+        private Consumer<Watermark> watermarkEmitter;
+
+        public WrappedDataOutput() {}
+
+        public void setWatermarkEmitter(Consumer<Watermark> watermarkEmitter) {
+            this.watermarkEmitter = watermarkEmitter;
+        }
+
+        @Override
+        public void emitRecord(StreamRecord<T> streamRecord) throws Exception {
+            throw new RuntimeException("Should not emit records with this output.");
+        }
+
+        @Override
+        public void emitWatermark(org.apache.flink.streaming.api.watermark.Watermark watermark)
+                throws Exception {
+            watermarkEmitter.accept(
+                    EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION.newWatermark(
+                            watermark.getTimestamp()));
+        }
+
+        @Override
+        public void emitWatermarkStatus(WatermarkStatus watermarkStatus) throws Exception {
+            watermarkEmitter.accept(
+                    EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.newWatermark(
+                            watermarkStatus.isIdle()));
+        }
+
+        @Override
+        public void emitLatencyMarker(LatencyMarker latencyMarker) throws Exception {
+            throw new RuntimeException("Should not emit LatencyMarker with this output.");
+        }
+
+        @Override
+        public void emitRecordAttributes(RecordAttributes recordAttributes) throws Exception {
+            throw new RuntimeException("Should not emit RecordAttributes with this output.");
+        }
+
+        @Override
+        public void emitWatermark(WatermarkEvent watermark) throws Exception {
+            throw new RuntimeException("Should not emit WatermarkEvent with this output.");
+        }
+    }
+}
diff --git a/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkHandler.java b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkHandler.java
new file mode 100644
--- /dev/null
+++ b/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/watermark/extension/eventtime/EventTimeWatermarkHandler.java
@@ -0,0 +1,220 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.runtime.watermark.extension.eventtime;
+
+import org.apache.flink.api.common.watermark.BoolWatermark;
+import org.apache.flink.api.common.watermark.LongWatermark;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
+import org.apache.flink.runtime.event.WatermarkEvent;
+import org.apache.flink.streaming.api.operators.InternalTimeServiceManager;
+import org.apache.flink.streaming.api.operators.Output;
+import org.apache.flink.streaming.api.watermark.Watermark;
+
+import javax.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.List;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * This class is used to handle {@link EventTimeExtension} related watermarks in operator, such as
+ * {@link EventTimeExtension#EVENT_TIME_WATERMARK_DECLARATION} and {@link
+ * EventTimeExtension#IDLE_STATUS_WATERMARK_DECLARATION}. It will emit event time watermark and idle
+ * status to downstream operators according to received watermarks.
+ */
+public class EventTimeWatermarkHandler {
+
+    /** number of input of operator, it should between 1 and 2 in current design. */
+    private final int numOfInput;
+
+    private final Output<?> output;
+
+    private final List<EventTimeWithIdleStatus> eventTimePerInput;
+
+    /**
+     * time service manager is used to advance event time in operator, and it may be null if the
+     * operator is not keyed.
+     */
+    @Nullable private final InternalTimeServiceManager<?> timeServiceManager;
+
+    private long lastEmitWatermark = Long.MIN_VALUE;
+
+    private boolean lastEmitIdleStatus = false;
+
+    /** A bitset to record whether the watermark has been received from each input. */
+    private final BitSet hasReceiveWatermarks;
+
+    public EventTimeWatermarkHandler(
+            int numOfInput,
+            Output<?> output,
+            @Nullable InternalTimeServiceManager<?> timeServiceManager) {
+        checkArgument(numOfInput >= 1 && numOfInput <= 2, "numOfInput should between 1 and 2");
+        this.numOfInput = numOfInput;
+        this.output = output;
+        this.eventTimePerInput = new ArrayList<>(numOfInput);
+        for (int i = 0; i < numOfInput; i++) {
+            eventTimePerInput.add(new EventTimeWithIdleStatus());
+        }
+        this.timeServiceManager = timeServiceManager;
+        this.hasReceiveWatermarks = new BitSet(numOfInput);
+    }
+
+    private EventTimeUpdateStatus processEventTime(long timestamp, int inputIndex)
+            throws Exception {
+        checkState(inputIndex < numOfInput);
+        hasReceiveWatermarks.set(inputIndex);
+        eventTimePerInput.get(inputIndex).setEventTime(timestamp);
+        eventTimePerInput.get(inputIndex).setIdleStatus(false);
+
+        return tryAdvanceEventTimeAndEmitWatermark();
+    }
+
+    private EventTimeUpdateStatus tryAdvanceEventTimeAndEmitWatermark() throws Exception {
+        // if current event time is larger than last emit watermark, emit it
+        long currentEventTime = getCurrentEventTime();
+        if (currentEventTime > lastEmitWatermark
+                && hasReceiveWatermarks.cardinality() == numOfInput) {
+            output.emitWatermark(
+                    new WatermarkEvent(
+                            EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION.newWatermark(
+                                    currentEventTime),
+                            false));
+            lastEmitWatermark = currentEventTime;
+            if (timeServiceManager != null) {
+                timeServiceManager.advanceWatermark(new Watermark(currentEventTime));
+            }
+            return EventTimeUpdateStatus.ofUpdatedWatermark(lastEmitWatermark);
+        }
+        return EventTimeUpdateStatus.NO_UPDATE;
+    }
+
+    private void processEventTimeIdleStatus(boolean isIdle, int inputIndex) {
+        checkState(inputIndex < numOfInput);
+        hasReceiveWatermarks.set(inputIndex);
+        eventTimePerInput.get(inputIndex).setIdleStatus(isIdle);
+        tryEmitEventTimeIdleStatus();
+    }
+
+    private void tryEmitEventTimeIdleStatus() {
+        // emit idle status if current idle status is different from last emit
+        boolean inputIdle = isAllInputIdle();
+        if (inputIdle != lastEmitIdleStatus) {
+            output.emitWatermark(
+                    new WatermarkEvent(
+                            EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.newWatermark(
+                                    inputIdle),
+                            false));
+            lastEmitIdleStatus = inputIdle;
+        }
+    }
+
+    private long getCurrentEventTime() {
+        long currentEventTime = Long.MAX_VALUE;
+        for (EventTimeWithIdleStatus eventTimeWithIdleStatus : eventTimePerInput) {
+            if (!eventTimeWithIdleStatus.isIdle()) {
+                currentEventTime =
+                        Math.min(currentEventTime, eventTimeWithIdleStatus.getEventTime());
+            }
+        }
+        return currentEventTime;
+    }
+
+    private boolean isAllInputIdle() {
+        boolean allInputIsIdle = true;
+        for (EventTimeWithIdleStatus eventTimeWithIdleStatus : eventTimePerInput) {
+            allInputIsIdle &= eventTimeWithIdleStatus.isIdle();
+        }
+        return allInputIsIdle;
+    }
+
+    public long getLastEmitWatermark() {
+        return lastEmitWatermark;
+    }
+
+    /**
+     * Process EventTimeWatermark/IdleStatusWatermark.
+     *
+     * <p>It's caller's responsibility to check whether the watermark is
+     * EventTimeWatermark/IdleStatusWatermark.
+     *
+     * @return the status of event time watermark update.
+     */
+    public EventTimeUpdateStatus processWatermark(
+            org.apache.flink.api.common.watermark.Watermark watermark, int inputIndex)
+            throws Exception {
+        if (EventTimeExtension.isEventTimeWatermark(watermark.getIdentifier())) {
+            long timestamp = ((LongWatermark) watermark).getValue();
+            return this.processEventTime(timestamp, inputIndex);
+        } else if (EventTimeExtension.isIdleStatusWatermark(watermark.getIdentifier())) {
+            boolean isIdle = ((BoolWatermark) watermark).getValue();
+            this.processEventTimeIdleStatus(isIdle, inputIndex);
+        }
+        return EventTimeUpdateStatus.NO_UPDATE;
+    }
+
+    /** This class represents event-time updated status. */
+    public static class EventTimeUpdateStatus {
+
+        public static final EventTimeUpdateStatus NO_UPDATE = new EventTimeUpdateStatus(false, -1L);
+
+        private final boolean isEventTimeUpdated;
+
+        private final long newEventTime;
+
+        private EventTimeUpdateStatus(boolean isEventTimeUpdated, long newEventTime) {
+            this.isEventTimeUpdated = isEventTimeUpdated;
+            this.newEventTime = newEventTime;
+        }
+
+        public boolean isEventTimeUpdated() {
+            return isEventTimeUpdated;
+        }
+
+        public long getNewEventTime() {
+            return newEventTime;
+        }
+
+        public static EventTimeUpdateStatus ofUpdatedWatermark(long newEventTime) {
+            return new EventTimeUpdateStatus(true, newEventTime);
+        }
+    }
+
+    static class EventTimeWithIdleStatus {
+        private long eventTime = Long.MIN_VALUE;
+        private boolean isIdle = false;
+
+        public long getEventTime() {
+            return eventTime;
+        }
+
+        public void setEventTime(long eventTime) {
+            this.eventTime = Math.max(this.eventTime, eventTime);
+        }
+
+        public boolean isIdle() {
+            return isIdle;
+        }
+
+        public void setIdleStatus(boolean idle) {
+            isIdle = idle;
+        }
+    }
+}
diff --git a/flink-runtime/src/main/java/org/apache/flink/streaming/util/watermark/WatermarkUtils.java b/flink-runtime/src/main/java/org/apache/flink/streaming/util/watermark/WatermarkUtils.java
--- a/flink-runtime/src/main/java/org/apache/flink/streaming/util/watermark/WatermarkUtils.java
+++ b/flink-runtime/src/main/java/org/apache/flink/streaming/util/watermark/WatermarkUtils.java
@@ -21,6 +21,7 @@
 import org.apache.flink.api.common.functions.Function;
 import org.apache.flink.api.common.watermark.Watermark;
 import org.apache.flink.api.common.watermark.WatermarkDeclaration;
+import org.apache.flink.datastream.api.extension.eventtime.EventTimeExtension;
 import org.apache.flink.datastream.api.function.ProcessFunction;
 import org.apache.flink.runtime.asyncprocessing.operators.AbstractAsyncStateUdfStreamOperator;
 import org.apache.flink.streaming.api.graph.StreamGraph;
@@ -29,9 +30,12 @@
 import org.apache.flink.streaming.api.operators.SourceOperatorFactory;
 import org.apache.flink.streaming.api.operators.StreamOperator;
 import org.apache.flink.streaming.runtime.watermark.AbstractInternalWatermarkDeclaration;
+import org.apache.flink.streaming.runtime.watermark.WatermarkCombiner;
+import org.apache.flink.streaming.runtime.watermark.extension.eventtime.EventTimeWatermarkCombiner;
 
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -95,4 +99,26 @@ private static Collection<? extends WatermarkDeclaration> getWatermarkDeclaratio
                 .map(AbstractInternalWatermarkDeclaration::from)
                 .collect(Collectors.toSet());
     }
+
+    /** Create watermark combiners if there are event time watermark declarations. */
+    public static void addEventTimeWatermarkCombinerIfNeeded(
+            Set<AbstractInternalWatermarkDeclaration<?>> watermarkDeclarationSet,
+            Map<String, WatermarkCombiner> watermarkCombiners,
+            int numberOfInputChannels) {
+        if (watermarkDeclarationSet.stream()
+                .anyMatch(
+                        declaration ->
+                                EventTimeExtension.isEventTimeWatermark(
+                                        declaration.getIdentifier()))) {
+            // create event time watermark combiner
+            EventTimeWatermarkCombiner eventTimeWatermarkCombiner =
+                    new EventTimeWatermarkCombiner(numberOfInputChannels);
+            watermarkCombiners.put(
+                    EventTimeExtension.EVENT_TIME_WATERMARK_DECLARATION.getIdentifier(),
+                    eventTimeWatermarkCombiner);
+            watermarkCombiners.put(
+                    EventTimeExtension.IDLE_STATUS_WATERMARK_DECLARATION.getIdentifier(),
+                    eventTimeWatermarkCombiner);
+        }
+    }
 }