dispatcher_progress_watchdog_timeout

Since: Dev Builds Only

The functionality described in this section requires a dev build of KumoMTA. You can obtain a dev build by following the instructions in the Installation section.

Sets the maximum duration a connection-handling dispatcher task for this egress path may go without making any forward progress before the maintainer aborts it.

kumo.on('get_egress_path_config', function(domain, source_name, site_name)
  return kumo.make_egress_path {
    dispatcher_progress_watchdog_timeout = '5m',
  }
end)

The value is a humantime duration string (e.g. '30s', '2m', '10m'), or nil (the default) to use the value derived at runtime from the egress path's other timeouts and the scheduled queue's protocol. For SMTP-family protocols the derived value is max(2 * longest per-command timeout, 60s); for protocols that delegate to user code or external services and do not expose a per-operation timeout, it is 10 minutes.

If you set a max_batch_latency larger than the derived default, set this option explicitly so the watchdog does not flag batch accumulation as a wedge.

When the watchdog fires, the connection's in-flight message is returned to the scheduled queue for another delivery attempt, and a Delayed record is written to the delivery log identifying the watchdog as the cause:

{
  "type": "Delayed",
  "recipient": "victim@wedge.example.com",
  "queue": "wedge.example.com",
  "response": {
    "code": 451,
    "enhanced_code": {"class": 4, "subject": 4, "detail": 1},
    "content": "dispatcher watchdog aborted task; phase=DeliveringMessage detail=\"lua: send\" session=db5e6704-05d3-4c8b-9cac-e3edd39e5c7a age=2s 481ms 890us 590ns time_in_phase=2s 478ms 972us 45ns"
  },
  "session_id": "db5e6704-05d3-4c8b-9cac-e3edd39e5c7a"
}

The session value embedded in the response, and the session_id field on the log record, both match the id present on the diagnostic that kumod logs at the time of the abort, so the two can be correlated.

The dispatcher_watchdog_aborted_total prometheus counter increments each time the watchdog fires.