# Celery: Workers Guide (time limits, remote control)

## Metadata

| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | background-work-limits |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | Celery: Workers Guide (time limits, remote control) |
| Source URL | https://docs.celeryq.dev/en/stable/userguide/workers.html |
| Source publisher / author | Celery project |
| Source type | vendor docs |
| Source date (published) | Unknown — not stated |
| Date researched | 2026-10-25 |
| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
| Research method | direct page fetch |
| Confidence | High |
| Status | Active |

## Summary

The current Celery worker guide, read for time limits and revocation.

## Key findings

- Soft time limit raises `SoftTimeLimitExceeded` inside the task so it can clean up; the hard limit cannot be caught and force-terminates the task.
- Time limits work in the prefork and gevent pools; the gevent pool does not implement soft limits; limits do not work on platforms without SIGUSR1.
- `revoke` skips a task that has not started; it does not stop a running task unless `terminate` is set, which terminates the worker child (default signal TERM, configurable).
- `--max-tasks-per-child` and `--max-memory-per-child` replace a worker process after N tasks or a resident-memory ceiling, containing leaks.
- Autoscale keeps a minimum number of processes and grows to a maximum under load (`--autoscale=10,3`).

## Pros / strengths

Shows the soft-before-hard ordering and that cancelling a running job needs an explicit escalation.

## Cons / limitations / caveats

Process-pool specifics; time limits depend on signals, which tai's cooperative agents cannot rely on.

## Relevance to tai

Pattern for tai's cancel path: first a soft cancel the worker can honor (cancel flag read between steps, `cap.cancel` to a CAP agent), and only then the hard stop (closing the session after `ORCH_CANCEL_GRACE`). Replacing a worker after a bounded amount of work is the same idea as depth and step caps.

## Changelog

| Date | Change |
|---|---|
| 2026-10-25 | Initial dossier created. |