This document describes the current stable version of Celery (5.4). For development docs, go here.

Change history for Celery 2.4



2011-12-02 05:00 p.m. GMT


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  • Periodic task interval schedules were accidentally rounded down, resulting in some periodic tasks being executed early.

  • Logging of humanized times in the beat log is now more detailed.

  • New Backends and Brokers section in the Getting Started part of the Documentation

    This replaces the old “Other queues” tutorial, and adds documentation for MongoDB, Beanstalk and CouchDB.



2011-11-25 04:00 p.m. GMT


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Security Fixes

  • [Security: CELERYSA-0001] Daemons would set effective id’s rather than real id’s when the --uid/ --gid arguments to celery multi, celeryd_detach, celery beat and celery events were used.

    This means privileges weren’t properly dropped, and that it would be possible to regain supervisor privileges later.


  • Processes pool: Fixed rare deadlock at shutdown (Issue #523).

    Fix contributed by Ionel Maries Christian.

  • Webhook tasks issued the wrong HTTP POST headers (Issue #515).

    The Content-Type header has been changed from application/jsonapplication/x-www-form-urlencoded, and adds a proper Content-Length header.

    Fix contributed by Mitar.

  • Daemonization tutorial: Adds a configuration example using Django and virtualenv together (Issue #505).

    Contributed by Juan Ignacio Catalano.

  • generic init-scripts now automatically creates log and pid file directories (Issue #545).

    Contributed by Chris Streeter.



2011-11-22 06:00 p.m. GMT


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  • Fixes module import typo in celeryctl (Issue #538).

    Fix contributed by Chris Streeter.



2011-11-14 12:00 p.m. GMT


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  • Program module no longer uses relative imports so that it’s possible to do python -m



2011-11-07 06:00 p.m. GMT


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  • celeryctl inspect commands was missing output.

  • processes pool: Decrease polling interval for less idle CPU usage.

  • processes pool: MaybeEncodingError wasn’t wrapped in ExceptionInfo (Issue #524).

  • worker: would silence errors occurring after task consumer started.

  • logging: Fixed a bug where unicode in stdout redirected log messages couldn’t be written (Issue #522).



2011-11-04 04:00 p.m. GMT


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Important Notes

  • Now supports Python 3.

  • Fixed deadlock in worker process handling (Issue #496).

    A deadlock could occur after spawning new child processes because the logging library’s mutex wasn’t properly reset after fork.

    The symptoms of this bug affecting would be that the worker simply stops processing tasks, as none of the workers child processes are functioning. There was a greater chance of this bug occurring with maxtasksperchild or a time-limit enabled.

    This is a workaround for

    Be aware that while this fixes the logging library lock, there could still be other locks initialized in the parent process, introduced by custom code.

    Fix contributed by Harm Verhagen.

  • AMQP Result backend: Now expires results by default.

    The default expiration value is now taken from the CELERY_TASK_RESULT_EXPIRES setting.

    The old CELERY_AMQP_TASK_RESULT_EXPIRES setting has been deprecated and will be removed in version 4.0.

    Note that this means that the result backend requires RabbitMQ 2.1.0 or higher, and that you have to disable expiration if you’re running with an older version. You can do so by disabling the CELERY_TASK_RESULT_EXPIRES setting:

  • Eventlet: Fixed problem with shutdown (Issue #457).

  • Broker transports can be now be specified using URLs

    The broker can now be specified as a URL instead. This URL must have the format:


    for example the default broker is written as:


    The scheme is required, so that the host is identified as a URL and not just a host name. User, password, port and virtual_host are optional and defaults to the particular transports default value.


    Note that the path component (virtual_host) always starts with a forward-slash. This is necessary to distinguish between the virtual host '' (empty) and '/', which are both acceptable virtual host names.

    A virtual host of '/' becomes:


    and a virtual host of '' (empty) becomes:


    So the leading slash in the path component is always required.

    In addition the BROKER_URL setting has been added as an alias to BROKER_HOST. Any broker setting specified in both the URL and in the configuration will be ignored, if a setting isn’t provided in the URL then the value from the configuration will be used as default.

    Also, programs now support the --broker option to specify a broker URL on the command-line:

    $ celery worker -b redis://localhost
    $ celery inspect -b amqp://guest:guest@localhost//e

    The environment variable CELERY_BROKER_URL can also be used to easily override the default broker used.

  • The deprecated celery.loaders.setup_loader() function has been removed.

  • The CELERY_TASK_ERROR_WHITELIST setting has been replaced by a more flexible approach (Issue #447).

    The error mail sending logic is now available as Task.ErrorMail, with the implementation (for reference) in celery.utils.mail.

    The error mail class can be sub-classed to gain complete control of when error messages are sent, thus removing the need for a separate white-list setting.

    The CELERY_TASK_ERROR_WHITELIST setting has been deprecated, and will be removed completely in version 4.0.

  • Additional Deprecations

    The following functions has been deprecated and is scheduled for removal in version 4.0:

    Old function












    The following settings has been deprecated and is scheduled for removal in version 4.0:

    Old setting



    celery worker --loglevel=


    celery worker --logfile=


    celery beat --loglevel=


    celery beat --logfile=


    celerymon --loglevel=


    celerymon --logfile=


  • No longer depends on

  • Now depends on Kombu 1.4.3.

  • CELERY_IMPORTS can now be a scalar value (Issue #485).

    It’s too easy to forget to add the comma after the sole element of a tuple, and this is something that often affects newcomers.

    The docs should probably use a list in examples, as using a tuple for this doesn’t even make sense. Nonetheless, there are many tutorials out there using a tuple, and this change should be a help to new users.

    Suggested by @jsaxon-cars.

  • Fixed a memory leak when using the thread pool (Issue #486).

    Contributed by Kornelijus Survila.

  • The statedb wasn’t saved at exit.

    This has now been fixed and it should again remember previously revoked tasks when a --statedb is enabled.

  • Adds EMAIL_USE_TLS to enable secure SMTP connections (Issue #418).

    Contributed by Stefan Kjartansson.

  • Now handles missing fields in task messages as documented in the message format documentation.

    • Missing required field throws InvalidTaskError

    • Missing args/kwargs is assumed empty.

    Contributed by Chris Chamberlin.

  • Fixed race condition in (celerymon/celeryev) where task info would be removed while iterating over it (Issue #501).

  • The Cache, Cassandra, MongoDB, Redis and Tyrant backends now respects the CELERY_RESULT_SERIALIZER setting (Issue #435).

    This means that only the database (Django/SQLAlchemy) backends currently doesn’t support using custom serializers.

    Contributed by Steeve Morin

  • Logging calls no longer manually formats messages, but delegates that to the logging system, so tools like Sentry can easier work with the messages (Issue #445).

    Contributed by Chris Adams.

  • multi now supports a stop_verify command to wait for processes to shutdown.

  • Cache backend didn’t work if the cache key was unicode (Issue #504).

    Fix contributed by Neil Chintomby.

  • New setting CELERY_RESULT_DB_SHORT_LIVED_SESSIONS added, which if enabled will disable the caching of SQLAlchemy sessions (Issue #449).

    Contributed by Leo Dirac.

  • All result backends now implements __reduce__ so that they can be pickled (Issue #441).

    Fix contributed by Remy Noel

  • multi didn’t work on Windows (Issue #472).

  • New-style CELERY_REDIS_* settings now takes precedence over the old REDIS_* configuration keys (Issue #508).

    Fix contributed by Joshua Ginsberg

  • Generic beat init-script no longer sets bash -e (Issue #510).

    Fix contributed by Roger Hu.

  • Documented that Chords don’t work well with redis-server versions before 2.2.

    Contributed by Dan McGee.

  • The CELERYBEAT_MAX_LOOP_INTERVAL setting wasn’t respected.

  • inspect.registered_tasks renamed to inspect.registered for naming consistency.

    The previous name is still available as an alias.

    Contributed by Mher Movsisyan

  • Worker logged the string representation of args and kwargs without safe guards (Issue #480).

  • RHEL init-script: Changed worker start-up priority.

    The default start / stop priorities for MySQL on RHEL are:

    # chkconfig: - 64 36

    Therefore, if Celery is using a database as a broker / message store, it should be started after the database is up and running, otherwise errors will ensue. This commit changes the priority in the init-script to:

    # chkconfig: - 85 15

    which are the default recommended settings for 3-rd party applications and assure that Celery will be started after the database service & shut down before it terminates.

    Contributed by Yury V. Zaytsev.

  • KeyValueStoreBackend.get_many didn’t respect the timeout argument (Issue #512).

  • beat/events’s --workdir option didn’t chdir(2) before after configuration was attempted (Issue #506).

  • After deprecating 2.4 support we can now name modules correctly, since we can take use of absolute imports.

    Therefore the following internal modules have been renamed:

    celery.concurrency.evlet -> celery.concurrency.eventlet celery.concurrency.evg -> celery.concurrency.gevent

  • AUTHORS file is now sorted alphabetically.

    Also, as you may have noticed the contributors of new features/fixes are now mentioned in the Changelog.