[
 {"type": "http_json", "url": "http://127.0.0.1:9000/health", "entity": "app:api",
  "signals": {"queue_depth": "queue.depth", "p95_ms": "latency.p95"}},
 {"type": "prometheus", "url": "http://127.0.0.1:9100/metrics", "entity": "node", "match": "^node_(load1|filesystem_avail_bytes)"},
 {"type": "command", "cmd": ["sh", "-c", "echo pending=$(ls /var/spool/myqueue | wc -l)"], "entity": "app:queue", "regex": "(\\w+)=([-\\d.]+)"}
]