This document describes the current stable version of Celery (3.1). For development docs, go here.

Change history

This document contains change notes for bugfix releases in the 3.1.x series (Cipater), please see What’s new in Celery 3.1 (Cipater) for an overview of what’s new in Celery 3.1.


release-date:2014-04-16 11:00 P.M UTC
release-by:Ask Solem
  • Now compatible with RabbitMQ 3.3.0

    You need to run Celery 3.1.11 or later when using RabbitMQ 3.3, and if you use the librabbitmq module you also have to upgrade to librabbitmq 1.5.0:

    $ pip install -U librabbitmq
  • Requirements:

    • Now depends on Kombu 3.0.15.
    • Now depends on billiard
    • Bundle celery[librabbitmq] now depends on librabbitmq 1.5.0.
  • Tasks: The CELERY_DEFAULT_DELIVERY_MODE setting was being ignored (Issue #1953).

  • Worker: New --heartbeat-interval can be used to change the time (in seconds) between sending event heartbeats.

    Contributed by Matthew Duggan and Craig Northway.

  • App: Fixed memory leaks occurring when creating lots of temporary app instances (Issue #1949).

  • MongoDB: SSL configuration with non-MongoDB transport breaks MongoDB results backend (Issue #1973).

    Fix contributed by Brian Bouterse.

  • Logging: The color formatter accidentally modified record.msg (Issue #1939).

  • Results: Fixed problem with task trails being stored multiple times, causing result.collect() to hang (Issue #1936, Issue #1943).

  • Results: ResultSet now implements a .backend attribute for compatibility with AsyncResult.

  • Results: .forget() now also clears the local cache.

  • Results: Fixed problem with multiple calls to result._set_cache (Issue #1940).

  • Results: join_native populated result cache even if disabled.

  • Results: The YAML result serializer should now be able to handle storing exceptions.

  • Worker: No longer sends task error emails for expected errors (in @task(throws=(..., ))).

  • Canvas: Fixed problem with exception deserialization when using the JSON serializer (Issue #1987).

  • Eventlet: Fixes crash when celery.contrib.batches attempted to cancel a non-existing timer (Issue #1984).

  • Can now import celery.version_info_t, and celery.five (Issue #1968).


release-date:2014-03-22 09:40 P.M UTC
release-by:Ask Solem
  • Requirements:

    • Now depends on Kombu 3.0.14.
  • Results:

    Reliability improvements to the SQLAlchemy database backend. Previously the connection from the MainProcess was improperly shared with the workers. (Issue #1786)

  • Redis: Important note about events (Issue #1882).

    There is a new transport option for Redis that enables monitors to filter out unwanted events. Enabling this option in the workers will increase performance considerably:

    BROKER_TRANSPORT_OPTIONS = {'fanout_patterns': True}

    Enabling this option means that your workers will not be able to see workers with the option disabled (or is running an older version of Celery), so if you do enable it then make sure you do so on all nodes.

    See redis-caveats-fanout-patterns.

    This will be the default in Celery 3.2.

  • Results: The celery.AsyncResult object now keeps a local cache of the final state of the task.

    This means that the global result cache can finally be disabled, and you can do so by setting CELERY_MAX_CACHED_RESULTS to -1. The lifetime of the cache will then be bound to the lifetime of the result object, which will be the default behavior in Celery 3.2.

  • Events: The “Substantial drift” warning message is now logged once per node name only (Issue #1802).

  • Worker: Ability to use one log file per child process when using the prefork pool.

    This can be enabled by using the new %i and %I format specifiers for the log file name. See Prefork pool process index.

  • Redis: New experimental chord join implementation.

    This is an optimization for chords when using the Redis result backend, where the join operation is now considerably faster and using less resources than the previous strategy.

    The new option can be set in the result backend URL:

    CELERY_RESULT_BACKEND = ‘redis://localhost?new_join=1’

    This must be enabled manually as it’s incompatible with workers and clients not using it, so be sure to enable the option in all clients and workers if you decide to use it.

  • Multi: With -opt:index (e.g. -c:1) the index now always refers to the position of a node in the argument list.

    This means that referring to a number will work when specifying a list of node names and not just for a number range:

    celery multi start A B C D -c:1 4 -c:2-4 8

    In this example 1 refers to node A (as it’s the first node in the list).

  • Signals: The sender argument to Signal.connect can now be a proxy object, which means that it can be used with the task decorator (Issue #1873).

  • Task: A regression caused the queue argument to Task.retry to be ignored (Issue #1892).

  • App: Fixed error message for config_from_envvar().

    Fix contributed by Dmitry Malinovsky.

  • Canvas: Chords can now contain a group of other chords (Issue #1921).

  • Canvas: Chords can now be combined when using the amqp result backend (a chord where the callback is also a chord).

  • Canvas: Calling result.get() for a chain task will now complete even if one of the tasks in the chain is ignore_result=True (Issue #1905).

  • Canvas: Worker now also logs chord errors.

  • Canvas: A chord task raising an exception will now result in any errbacks (link_error) to the chord callback to also be called.

  • Results: Reliability improvements to the SQLAlchemy database backend (Issue #1786).

    Previously the connection from the MainProcess was improperly inherited by child processes.

    Fix contributed by Ionel Cristian Mărieș.

  • Task: Task callbacks and errbacks are now called using the group primitive.

  • Task: Task.apply now properly sets request.headers (Issue #1874).

  • Worker: Fixed UnicodeEncodeError occuring when worker is started by supervisord.

    Fix contributed by Codeb Fan.

  • Beat: No longer attempts to upgrade a newly created database file (Issue #1923).

  • Beat: New setting :setting:CELERYBEAT_SYNC_EVERY can be be used to control file sync by specifying the number of tasks to send between each sync.

    Contributed by Chris Clark.

  • Commands: celery inspect memdump no longer crashes if the psutil module is not installed (Issue #1914).

  • Worker: Remote control commands now always accepts json serialized messages (Issue #1870).

  • Worker: Gossip will now drop any task related events it receives by mistake (Issue #1882).


release-date:2014-02-10 06:43 P.M UTC
release-by:Ask Solem
  • Requirements:

    • Now depends on Kombu 3.0.12.
  • Prefork pool: Better handling of exiting child processes.

    Fix contributed by Ionel Cristian Mărieș.

  • Prefork pool: Now makes sure all file descriptors are removed from the hub when a process is cleaned up.

    Fix contributed by Ionel Cristian Mărieș.

  • New Sphinx extension: for autodoc documentation of tasks: celery.contrib.spinx (Issue #1833).

  • Django: Now works with Django 1.7a1.

  • Task: Task.backend is now a property that forwards to app.backend if no custom backend has been specified for the task (Issue #1821).

  • Generic init scripts: Fixed bug in stop command.

    Fix contributed by Rinat Shigapov.

  • Generic init scripts: Fixed compatibility with GNU stat.

    Fix contributed by Paul Kilgo.

  • Generic init scripts: Fixed compatibility with the minimal dash shell (Issue #1815).

  • Commands: The celery amqp basic.publish command was not working properly.

    Fix contributed by Andrey Voronov.

  • Commands: Did no longer emit an error message if the pidfile exists and the process is still alive (Issue #1855).

  • Commands: Better error message for missing arguments to preload options (Issue #1860).

  • Commands: celery -h did not work because of a bug in the argument parser (Issue #1849).

  • Worker: Improved error message for message decoding errors.

  • Time: Now properly parses the Z timezone specifier in ISO 8601 date strings.

    Fix contributed by Martin Davidsson.

  • Worker: Now uses the negotiated heartbeat value to calculate how often to run the heartbeat checks.

  • Beat: Fixed problem with beat hanging after the first schedule iteration (Issue #1822).

    Fix contributed by Roger Hu.

  • Signals: The header argument to before_task_publish is now always a dictionary instance so that signal handlers can add headers.

  • Worker: A list of message headers is now included in message related errors.


release-date:2014-01-17 10:45 P.M UTC
release-by:Ask Solem
  • Worker: The event loop was not properly reinitialized at consumer restart which would force the worker to continue with a closed epoll instance on Linux, resulting in a crash.

  • Events: Fixed issue with both heartbeats and task events that could result in the data not being kept in sorted order.

    As a result this would force the worker to log “heartbeat missed” events even though the remote node was sending heartbeats in a timely manner.

  • Results: The pickle serializer no longer converts group results to tuples, and will keep the original type (Issue #1750).

  • Results: ResultSet.iterate is now pending deprecation.

    The method will be deprecated in version 3.2 and removed in version 3.3.

    Use result.get(callback=) (or result.iter_native() where available) instead.

  • Worker|eventlet/gevent: A regression caused Ctrl+C to be ineffective for shutdown.

  • Redis result backend: Now using a pipeline to store state changes for improved performance.

    Contributed by Pepijn de Vos.

  • Redis result backend: Will now retry storing the result if disconnected.

  • Worker|gossip: Fixed attribute error occurring when another node leaves.

    Fix contributed by Brodie Rao.

  • Generic init scripts: Now runs a check at startup to verify that any configuration scripts are owned by root and that they are not world/group writeable.

    The init script configuration is a shell script executed by root, so this is a preventive measure to ensure that users do not leave this file vulnerable to changes by unprivileged users.


    Note that upgrading celery will not update the init scripts, instead you need to manually copy the improved versions from the source distribution:

  • Commands: The celery purge command now warns that the operation will delete all tasks and prompts the user for confirmation.

    A new -f was added that can be used to disable interactive mode.

  • Task: .retry() did not raise the value provided in the exc argument when called outside of an error context (Issue #1755).

  • Commands: The celery multi command did not forward command line configuration to the target workers.

    The change means that multi will forward the special -- argument and configuration content at the end of the arguments line to the specified workers.

    Example using command-line configuration to set a broker heartbeat from celery multi:

    $ celery multi start 1 -c3 -- broker.heartbeat=30

    Fix contributed by Antoine Legrand.

  • Canvas: chain.apply_async() now properly forwards execution options.

    Fix contributed by Konstantin Podshumok.

  • Redis result backend: Now takes connection_pool argument that can be used to change the connection pool class/constructor.

  • Worker: Now truncates very long arguments and keyword arguments logged by the pool at debug severity.

  • Worker: The worker now closes all open files on SIGHUP (regression) (Issue #1768).

    Fix contributed by Brodie Rao

  • Worker: Will no longer accept remote control commands while the worker startup phase is incomplete (Issue #1741).

  • Commands: The output of the event dump utility (celery events -d) can now be piped into other commands.

  • Documentation: The RabbitMQ installation instructions for OS X was updated to use modern homebrew practices.

    Contributed by Jon Chen.

  • Commands: The celery inspect conf utility now works.

  • Commands: The -no-color argument was not respected by all commands (Issue #1799).

  • App: Fixed rare bug with autodiscover_tasks() (Issue #1797).

  • Distribution: The sphinx docs will now always add the parent directory to path so that the current celery source code is used as a basis for API documentation (Issue #1782).

  • Documentation: Supervisord examples contained an extraneous ‘-‘ in a –logfile argument example.

    Fix contributed by Mohammad Almeer.


release-date:2013-12-17 06:00 P.M UTC
release-by:Ask Solem

Important Notes

Init script security improvements

Where the generic init scripts (for celeryd, and celerybeat) before delegated the responsibility of dropping privileges to the target application, it will now use su instead, so that the Python program is not trusted with superuser privileges.

This is not in reaction to any known exploit, but it will limit the possibility of a privilege escalation bug being abused in the future.

You have to upgrade the init scripts manually from this directory:

AMQP result backend

The 3.1 release accidentally left the amqp backend configured to be non-persistent by default.

Upgrading from 3.0 would give a “not equivalent” error when attempting to set or retrieve results for a task. That is unless you manually set the persistence setting:


This version restores the previous value so if you already forced the upgrade by removing the existing exchange you must either keep the configuration by setting CELERY_RESULT_PERSISTENT = False or delete the celeryresults exchange again.

Synchronous subtasks

Tasks waiting for the result of a subtask will now emit a RuntimeWarning warning when using the prefork pool, and in 3.2 this will result in an exception being raised.

It’s not legal for tasks to block by waiting for subtasks as this is likely to lead to resource starvation and eventually deadlock when using the prefork pool (see also Avoid launching synchronous subtasks).

If you really know what you are doing you can avoid the warning (and the future exception being raised) by moving the operation in a whitelist block:

from celery.result import allow_join_result

def misbehaving():
    result = other_task.delay()
    with allow_join_result():

Note also that if you wait for the result of a subtask in any form when using the prefork pool you must also disable the pool prefetching behavior with the worker -Ofair option.


  • Now depends on Kombu 3.0.8.

  • Now depends on billiard

  • Events: Fixed compatibility with non-standard json libraries that sends float as decimal.Decimal (Issue #1731)

  • Events: State worker objects now always defines attributes: active, processed, loadavg, sw_ident, sw_ver and sw_sys.

  • Worker: Now keeps count of the total number of tasks processed, not just by type (all_active_count).

  • Init scripts: Fixed problem with reading configuration file when the init script is symlinked to a runlevel (e.g. S02celeryd). (Issue #1740).

    This also removed a rarely used feature where you can symlink the script to provide alternative configurations. You instead copy the script and give it a new name, but perhaps a better solution is to provide arguments to CELERYD_OPTS to separate them:

    CELERYD_OPTS="-A:X1 x -A:X2 x -A:Y1 y -A:Y2 y"
  • Fallback chord unlock task is now always called after the chord header (Issue #1700).

    This means that the unlock task will not be started if there’s an error sending the header.

  • Celery command: Fixed problem with arguments for some control commands.

    Fix contributed by Konstantin Podshumok.

  • Fixed bug in utcoffset where the offset when in DST would be completely wrong (Issue #1743).

  • Worker: Errors occurring while attempting to serialize the result of a task will now cause the task to be marked with failure and a kombu.exceptions.EncodingError error.

    Fix contributed by Ionel Cristian Mărieș.

  • Worker with -B argument did not properly shut down the beat instance.

  • Worker: The %n and %h formats are now also supported by the --logfile, --pidfile and --statedb arguments.


    $ celery -A proj worker -n foo@%h --logfile=%n.log --statedb=%n.db
  • Redis/Cache result backends: Will now timeout if keys evicted while trying to join a chord.

  • The fallbock unlock chord task now raises Retry so that the retry even is properly logged by the worker.

  • Multi: Will no longer apply Eventlet/gevent monkey patches (Issue #1717).

  • Redis result backend: Now supports UNIX sockets.

    Like the Redis broker transport the result backend now also supports using redis+socket:///tmp/redis.sock URLs.

    Contributed by Alcides Viamontes Esquivel.

  • Events: Events sent by clients was mistaken for worker related events (Issue #1714).

    For events.State the tasks now have a Task.client attribute that is set when a task-sent event is being received.

    Also, a clients logical clock is not in sync with the cluster so they live in a “time bubble”. So for this reason monitors will no longer attempt to merge with the clock of an event sent by a client, instead it will fake the value by using the current clock with a skew of -1.

  • Prefork pool: The method used to find terminated processes was flawed in that it did not also take into account missing popen objects.

  • Canvas: group and chord now works with anon signatures as long as the group/chord object is associated with an app instance (Issue #1744).

    You can pass the app by using group(..., app=app).


release-date:2013-12-02 06:00 P.M UTC
release-by:Ask Solem
  • Now depends on billiard

  • Now depends on Kombu 3.0.7.

  • Fixed problem where Mingle caused the worker to hang at startup (Issue #1686).

  • Beat: Would attempt to drop privileges twice (Issue #1708).

  • Windows: Fixed error with geteuid not being available (Issue #1676).

  • Tasks can now provide a list of expected error classes (Issue #1682).

    The list should only include errors that the task is expected to raise during normal operation:

    @task(throws=(KeyError, HttpNotFound))

    What happens when an exceptions is raised depends on the type of error:

    • Expected errors (included in Task.throws)

      Will be logged using severity INFO, and traceback is excluded.

    • Unexpected errors

      Will be logged using severity ERROR, with traceback included.

  • Cache result backend now compatible with Python 3 (Issue #1697).

  • CentOS init script: Now compatible with sys-v style init symlinks.

    Fix contributed by Jonathan Jordan.

  • Events: Fixed problem when task name is not defined (Issue #1710).

    Fix contributed by Mher Movsisyan.

  • Task: Fixed unbound local errors (Issue #1684).

    Fix contributed by Markus Ullmann.

  • Canvas: Now unrolls groups with only one task (optimization) (Issue #1656).

  • Task: Fixed problem with eta and timezones.

    Fix contributed by Alexander Koval.

  • Django: Worker now performs model validation (Issue #1681).

  • Task decorator now emits less confusing errors when used with incorrect arguments (Issue #1692).

  • Task: New method Task.send_event can be used to send custom events to Flower and other monitors.

  • Fixed a compatibility issue with non-abstract task classes

  • Events from clients now uses new node name format (gen<pid>@<hostname>).

  • Fixed rare bug with Callable not being defined at interpreter shutdown (Issue #1678).

    Fix contributed by Nick Johnson.

  • Fixed Python 2.6 compatibility (Issue #1679).


release-date:2013-11-21 06:20 P.M UTC
release-by:Ask Solem
  • Now depends on Kombu 3.0.6.

  • Now depends on billiard

  • App: config_from_object is now lazy (Issue #1665).

  • App: autodiscover_tasks is now lazy.

    Django users should now wrap access to the settings object in a lambda:

    app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)

    this ensures that the settings object is not prepared prematurely.

  • Fixed regression for --app argument experienced by some users (Issue #1653).

  • Worker: Now respects the --uid and --gid arguments even if --detach is not enabled.

  • Beat: Now respects the --uid and --gid arguments even if --detach is not enabled.

  • Python 3: Fixed unorderable error occuring with the worker -B argument enabled.

  • celery.VERSION is now a named tuple.

  • maybe_signature(list) is now applied recursively (Issue #1645).

  • celery shell command: Fixed IPython.frontend deprecation warning.

  • The default app no longer includes the builtin fixups.

    This fixes a bug where celery multi would attempt to load the Django settings module before entering the target working directory.

  • The Django daemonization tutorial was changed.

    Users no longer have to explicitly export DJANGO_SETTINGS_MODULE in /etc/default/celeryd when the new project layout is used.

  • Redis result backend: expiry value can now be 0 (Issue #1661).

  • Censoring settings now accounts for non-string keys (Issue #1663).

  • App: New autofinalize option.

    Apps are automatically finalized when the task registry is accessed. You can now disable this behavior so that an exception is raised instead.


    app = Celery(autofinalize=False)
    # raises RuntimeError
    tasks = app.tasks
    def add(x, y):
        return x + y
    # raises RuntimeError
    add.delay(2, 2)
    # no longer raises:
    tasks = app.tasks
    add.delay(2, 2)
  • The worker did not send monitoring events during shutdown.

  • Worker: Mingle and gossip is now automatically disabled when used with an unsupported transport (Issue #1664).

  • celery command: Preload options now supports the rare --opt value format (Issue #1668).

  • celery command: Accidentally removed options appearing before the subcommand, these are now moved to the end instead.

  • Worker now properly responds to inspect stats commands even if received before startup is complete (Issue #1659).

  • task_postrun is now sent within a finally block, to make sure the signal is always sent.

  • Beat: Fixed syntax error in string formatting.

    Contributed by nadad.

  • Fixed typos in the documentation.

    Fixes contributed by Loic Bistuer, sunfinite.

  • Nested chains now works properly when constructed using the chain type instead of the | operator (Issue #1656).


release-date:2013-11-15 11:40 P.M UTC
release-by:Ask Solem
  • Now depends on Kombu 3.0.5.

  • Now depends on billiard

  • Worker accidentally set a default socket timeout of 5 seconds.

  • Django: Fixup now sets the default app so that threads will use the same app instance (e.g. for runserver).

  • Worker: Fixed Unicode error crash at startup experienced by some users.

  • Calling .apply_async on an empty chain now works again (Issue #1650).

  • The celery multi show command now generates the same arguments as the start command does.

  • The --app argument could end up using a module object instead of an app instance (with a resulting crash).

  • Fixed a syntax error problem in the celerybeat init script.

    Fix contributed by Vsevolod.

  • Tests now passing on PyPy 2.1 and 2.2.


release-date:2013-11-13 00:55 A.M UTC
release-by:Ask Solem
  • Fixed compatibility problem with Python 2.7.0 - 2.7.5 (Issue #1637)

    unpack_from started supporting memoryview arguments in Python 2.7.6.

  • Worker: -B argument accidentally closed files used for logging.

  • Task decorated tasks now keep their docstring (Issue #1636)


release-date:2013-11-12 08:00 P.M UTC
release-by:Ask Solem
  • Now depends on billiard

  • No longer needs the billiard C extension to be installed.

  • The worker silently ignored task errors.

  • Django: Fixed ImproperlyConfigured error raised when no database backend specified.

    Fix contributed by j0hnsmith

  • Prefork pool: Now using with memoryview if available.

  • close_open_fds now uses os.closerange if available.

  • get_fdmax now takes value from sysconfig if possible.


release-date:2013-11-11 06:30 P.M UTC
release-by:Ask Solem
  • Now depends on billiard

  • Python 3: Fixed compatibility issues.

  • Windows: Accidentally showed warning that the billiard C extension was not installed (Issue #1630).

  • Django: Tutorial updated with a solution that sets a default DJANGO_SETTINGS_MODULE so that it doesn’t have to be typed in with the celery command.

    Also fixed typos in the tutorial, and added the settings required to use the Django database backend.

    Thanks to Chris Ward, orarbel.

  • Django: Fixed a problem when using the Django settings in Django 1.6.

  • Django: Fixup should not be applied if the django loader is active.

  • Worker: Fixed attribute error for human_write_stats when using the compatibility prefork pool implementation.

  • Worker: Fixed compatibility with billiard without C extension.

  • Inspect.conf: Now supports a with_defaults argument.

  • Group.restore: The backend argument was not respected.


release-date:2013-11-09 11:00 P.M UTC
release-by:Ask Solem

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