This document describes the current stable version of Celery (5.5). For development docs, go here.

celery.worker.worker

WorkController can be used to instantiate in-process workers.

The command-line interface for the worker is in celery.bin.worker, while the worker program is in celery.apps.worker.

The worker program is responsible for adding signal handlers, setting up logging, etc. This is a bare-bones worker without global side-effects (i.e., except for the global state stored in celery.worker.state).

The worker consists of several components, all managed by bootsteps (mod:celery.bootsteps).

class celery.worker.worker.WorkController(app=None, hostname=None, **kwargs)

Unmanaged worker instance.

class Blueprint(steps=None, name=None, on_start=None, on_close=None, on_stopped=None)

Worker bootstep blueprint.

default_steps = {'celery.worker.autoscale:WorkerComponent', 'celery.worker.components:Beat', 'celery.worker.components:Consumer', 'celery.worker.components:Hub', 'celery.worker.components:Pool', 'celery.worker.components:StateDB', 'celery.worker.components:Timer'}

name = 'Worker'

app = None

blueprint = None

exitcode = None

contains the exit code if a SystemExit event is handled.

info()

on_after_init(**kwargs)

on_before_init(**kwargs)

on_close()

on_consumer_ready(consumer)

on_init_blueprint()

on_start()

on_stopped()

pidlock = None

pool = None

prepare_args(**kwargs)

register_with_event_loop(hub)

reload(modules=None, reload=False, reloader=None)

rusage()

semaphore = None

setup_defaults(concurrency=None, loglevel='WARN', logfile=None, task_events=None, pool=None, consumer_cls=None, timer_cls=None, timer_precision=None, autoscaler_cls=None, pool_putlocks=None, pool_restarts=None, optimization=None, O=None, statedb=None, time_limit=None, soft_time_limit=None, scheduler=None, pool_cls=None, state_db=None, task_time_limit=None, task_soft_time_limit=None, scheduler_cls=None, schedule_filename=None, max_tasks_per_child=None, prefetch_multiplier=None, disable_rate_limits=None, worker_lost_wait=None, max_memory_per_child=None, **_kw)

setup_includes(includes)

setup_instance(queues=None, ready_callback=None, pidfile=None, include=None, use_eventloop=None, exclude_queues=None, **kwargs)

setup_queues(include, exclude=None)

should_use_eventloop()

signal_consumer_close()

start()

property state

stats()

stop(in_sighandler=False, exitcode=None)

Graceful shutdown of the worker server (Warm shutdown).

terminate(in_sighandler=False)

Not so graceful shutdown of the worker server (Cold shutdown).

wait_for_soft_shutdown()

Wait worker_soft_shutdown_timeout if soft shutdown is enabled.

To enable soft shutdown, set the worker_soft_shutdown_timeout in the configuration. Soft shutdown can be used to allow the worker to finish processing few more tasks before initiating a cold shutdown. This mechanism allows the worker to finish short tasks that are already in progress and requeue long-running tasks to be picked up by another worker.

Warning

If there are no tasks in the worker, the worker will not wait for the soft shutdown timeout even if it is set as it makes no sense to wait for the timeout when there are no tasks to process.