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What is supervision?

Every actor has a parent. When a child fails (panics, returns an error from a handler), the parent’s supervisor decides what to do. This keeps failures localized and recoverable.

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Strategies

StrategyEffect
OneForOneOnly the failing child is affected
OneForAllAll siblings are affected (e.g., all restarted)
Choose OneForOne when failures are independent; OneForAll when siblings share critical state.

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Directives

DirectiveAction
ResumeIgnore the failure; continue processing
RestartRe-initialize the child (PreStart runs again)
StopTerminate the child
EscalatePass the failure to the grandparent
Configure retry windows (max retries within a time period) to avoid infinite restart loops. After the window is exceeded, the supervisor can escalate.

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Supervisor configuration

Supervisors are created with supervisor.NewSupervisor(opts...) and passed via WithSupervisor when spawning. Key options:
OptionPurpose
WithDirective(errType, directive)Map a specific error type to a directive
WithAnyErrorDirective(directive)Catch-all for any error
WithRetry(maxRetries, timeout)Bound restarts within a time window
WithStrategy(strategy)OneForOne (default) or OneForAll
Directives: Resume, Restart, Stop, Escalate. When the retry window is exceeded, the supervisor escalates to the grandparent.