Sender { # Webhook Sender
n1: circle label:"Start"
n2: rectangle label:"Event occurs in system"
n3: rectangle label:"Build webhook payload"
n4: rectangle label:"Log delivery result"
n5: circle label:"End"
n1.handle(right) -> n2.handle(left)
n2.handle(right) -> n3.handle(left)
n3.handle(bottom) -> Delivery.n6.handle(top) [label="Send"]
n4.handle(right) -> n5.handle(left)
}
Delivery { # Webhook Delivery
n6: rectangle label:"Sign payload with HMAC"
n7: rectangle label:"POST to subscriber URL"
n8: diamond label:"Response status?"
n9: rectangle label:"Mark as delivered"
n10: rectangle label:"Schedule retry"
n11: diamond label:"Max retries reached?"
n12: rectangle label:"Mark as failed"
n6.handle(right) -> n7.handle(left)
n7.handle(right) -> n8.handle(left)
n8.handle(right) -> n9.handle(left) [label="2xx"]
n8.handle(bottom) -> n10.handle(top) [label="4xx/5xx"]
n9.handle(top) -> Sender.n4.handle(bottom) [label="Success"]
n10.handle(right) -> n11.handle(left)
n11.handle(right) -> n12.handle(left) [label="Yes"]
n11.handle(bottom) -> n7.handle(bottom) [label="No"]
n12.handle(top) -> Sender.n4.handle(bottom) [label="Failed"]
loop [retry up to 5 times] n7 n8 n10 n11
}
Receiver { # Webhook Receiver
n13: rectangle label:"Receive POST request"
n14: rectangle label:"Verify HMAC signature"
n15: diamond label:"Signature valid?"
n16: rectangle label:"Parse JSON payload"
n17: rectangle label:"Return 401 Unauthorized"
n18: rectangle label:"Process event"
n19: rectangle label:"Return 200 OK"
n13.handle(right) -> n14.handle(left)
n14.handle(right) -> n15.handle(left)
n15.handle(right) -> n16.handle(left) [label="Yes"]
n15.handle(bottom) -> n17.handle(top) [label="No"]
n16.handle(right) -> n18.handle(left)
n17.handle(top) -> Sender.n4.handle(bottom) [label="Rejected"]
n18.handle(right) -> n19.handle(left)
n19.handle(top) -> Sender.n4.handle(bottom) [label="Processed"]
}