Supervisor Strategies

The ProcessManager supports supervisor strategies that control which processes are restarted when one process in a group crashes. This follows the Erlang OTP supervisor model.

Strategies

How it works

When the reaper detects a crash and determines that a restart should occur (based on restart_on_exit, restart_trigger, and rate limiting), it reads the supervisor_strategy from the crashed process’s config.

• OneForOne - Only the crashed process is restarted. Other processes in the group are unaffected.
• OneForAll - All processes in the same label group are stopped and restarted. Each process gets its own backoff timer.
• RestForOne - The crashed process and all processes with a higher spawn_sequence in the same group are stopped and restarted.

Interaction with dependencies

When using OneForAll or RestForOne with dependencies, restart order follows the dependency chain. The compositor restarts first, then dependent processes start once the compositor is Running.

Cascade flag

When a process is cascade-killed (stopped because another process in its group crashed), it is marked with cascade_flag = true. The reaper skips supervisor strategy logic for cascade-killed processes and emits a Stopped event instead of triggering another restart cycle. This prevents recursive cascades.

Example

#![allow(unused)]
fn main() {
use process_manager::{ProcessConfig, ProcessManager, SupervisorStrategy, StdioConfig};

let manager = ProcessManager::new();

let config = ProcessConfig::builder()
    .command("my-service".to_string())
    .restart_on_exit(true)
    .supervisor_strategy(SupervisorStrategy::OneForAll)
    .stdout(StdioConfig::Null)
    .stderr(StdioConfig::Null)
    .build();

let id = manager.start("group-a", &config)?;
}