An arbitrary actor can be told to monitor other actors or Julia tasks. Monitored actors or tasks send a Down message with an exit reason to their monitor(s) before they terminate. A monitor then gives a warning or executes a specified action dispatched on the received reason.


Monitors do not forward Down messages. They give warnings or execute specified actions for Down signals (even with reason :normal). Monitoring is not bidirectional. If a monitor fails, the monitored actor gets no notification. Monitoring can be stopped with demonitor. An actor can have several monitors (if that makes sense).

You can see a script illustrating monitoring in the How-to section.