Module supervisor 

Erlang-style supervisor trees for hierarchical actor supervision.

This module implements the supervisor pattern from Erlang/OTP, providing fault-tolerant actor management with automatic restart policies and hierarchical supervision trees.

Overview

Supervisors manage child actors with configurable restart strategies:

• One-for-one: Restart only the failed child
• One-for-all: Restart all children when one fails
• Rest-for-one: Restart failed child and those started after it
• Simple one-for-one: No restart, just acknowledge failure

Example

use actor_kit::supervisor::{
    SupervisorTree, SupervisionStrategy, ChildSpec, RestartPolicy,
};
use std::time::Duration;

// Create a supervisor tree with one-for-one strategy
let mut tree = SupervisorTree::new(
    SupervisionStrategy::one_for_one(5, Duration::from_secs(60))
);

// Start a child actor under the root supervisor
let child_id = tree.start_child_under(
    tree.root(),
    ChildSpec {
        name: "worker-1".into(),
        actor_config: Default::default(),
        restart_policy: RestartPolicy::Permanent,
        shutdown_timeout: Duration::from_secs(30),
        significant: false,
    },
)?;

Structs

ActorConfig

Startup and behavioral configuration for a child actor, controlling parameters such as mailbox capacity, dispatch priority, and initialization arguments.

ChildSpec

Specification for a supervised child actor.

DegradationController

Graceful degradation controller that wraps a ResourceMonitor and makes admission-control decisions.

FnResourceMonitor

A resource monitor that reports Elevated when a closure returns true and Critical when a second closure returns true.

StaticResourceMonitor

A static resource monitor that always reports the same pressure level.

SupervisedChild

A child actor being supervised.

Supervisor

A supervisor that manages child actors.

SupervisorHandle

Thread-safe wrapper for supervisor operations.

SupervisorStats

Statistics about a supervisor’s children.

SupervisorTree

Hierarchical supervisor tree structure.

SupervisorTreeStats

Statistics for the entire supervisor tree.

Enums

ChildState

State of a supervised child.

DegradationDecision

Result of a graceful degradation decision.

EscalationAction

Action to take when max restarts are exceeded.

ExitReason

Why an actor terminated.

PressureLevel

Resource pressure level reported by a ResourceMonitor.

RestartPolicy

Restart policy for a supervised child.

SupervisionStrategy

How a supervisor should handle child failures.

SupervisorError

Error type for supervisor operations.

Traits

ResourceMonitor

Trait for monitoring system resource pressure.