Supervision

In GoAkt, the supervision mechanism enables you to specify the supervisor strategy to handle actor failures. That strategy is configured at the time of actor creation by using the SpawnOption method WithSupervisor. To define a custom supervisor strategy, call the NewSupervisor function and supply the desired options via SupervisorOption.

GoAkt also provides built-in error types to use with supervisor directives:

• PanicError: Wraps an error as an alternative to triggering the standard Go panic.

• InternalError: Serves as a wrapper for errors classified as internal.

• SpawnError: Recommended for situations where the creation of an actor fails

Example

supervisor := NewSupervisor(
	WithStrategy(OneForOneStrategy),
	WithDirective(PanicError{}, RestartDirective),
	WithDirective(&runtime.PanicNilError{}, RestartDirective),
	WithDirective(InternalError{}, ResumeDirective),
	WithDirective(SpawnError{}, ResumeDirective),
)

Strategies

GoAkt supports the following supervisor strategies:

• OneForOneStrategy: if a child actor fails, only that specific child actor is affected by the supervisor's Directive . This is the default supervisor strategy.

• OneForAllStrategy: if a child actor fails, that specific child actor and its siblings are affected by the supervisor's Directive .This strategy is particularly appropriate when the child actors are tightly coupled or interdependent—where the malfunction of one actor can adversely affect the overall functionality of the ensemble.

Directives

GoAkt supports the following supervisor directives:

• StopDirective: Instructs the supervisor to stop the failing actor along its siblings depending upon the strategy used.

• ResumeDirective: Instructs the supervisor to resume the failing actor without restarting it allowing it to continue processing messages (typically used for recoverable errors)

• RestartDirective: Instructs the supervisor to restart the failing actor along its siblings depending upon the strategy used, reinitialising its state or their states.

  With the RestartDirective directive, only the direct alive children of the given actor will be shutdown and respawned with their initial state. There are only two scenarios where an actor can supervise another actor:

  • It watches the given actor via the Watch method. With this method the parent actor can also listen to the Terminated message to decide what happens next to the child actor.

  • The actor to be supervised is a child of the given actor.

Note

GoAkt will suspend a faulty actor when there is no supervisor strategy set in place for the corresponding error type. Once can check the state of the actor using the IsSuspended method on the PID. A suspended actor can be restarted or shutdown, however it cannot handle any messages sent to it.