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Start vs Spawn

start is now the primary process-creation command. :::warning Deprecated sysg spawn is deprecated. Use sysg start --parent-pid ... for child-process workflows. :::

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Quick comparison

start (manifest/ad-hoc)start (child mode)spawn (deprecated)
Flagssysg start [--config ...] [-- command...]sysg start --parent-pid <pid> [--ttl ...] -- <cmd...>sysg spawn ...
LifecycleTop-level managed unit(s)Parent-attached child unitParent-attached child unit
Use caseCore services and ad-hoc unitsDynamic child workersLegacy compatibility

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start - Unified command

Manifest services: 
services:
  web:
    command: "python app.py"
    restart_policy: always
  database:
    command: "postgres"
    depends_on: []
Run with: 
$ sysg start
Ad-hoc single command: 
$ sysg start --name quick-task -- ./task.sh
Child-mode replacement for spawn: 
$ sysg start --parent-pid 12345 --name worker_1 --ttl 3600 -- python job.py

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Legacy spawn mapping

Existing invocations: 
$ sysg spawn --name worker_1 -- python job.py
Equivalent start command: 
$ sysg start --parent-pid <parent_pid> --name worker_1 -- python job.py
Use the term child mode for the former spawn workflow:
  • start in child mode (--parent-pid)
  • start in ad-hoc mode (command without --parent-pid)
  • start in manifest mode (no command)

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Example: Job queue with child mode

services:
  queue:
    command: "redis-server"
    restart_policy: always

  scheduler:
    command: "python scheduler.py"
    depends_on: ["queue"]
    spawn:
      mode: dynamic
      limit: 50
The scheduler reads from queue and spawns workers: 
# scheduler.py
import os
import subprocess

while job := queue.pop():
    subprocess.run(["sysg", "start", "--parent-pid", str(os.getpid()),
                    "--name", f"job_{job.id}",
                    "--ttl", "3600", "--", "python", "worker.py", job.id])

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See also