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

Change history for Celery 3.0

If you’re looking for versions prior to 3.0.x you should go to History.


release-date:2013-10-11 04:40 P.M BST
release-by:Ask Solem
  • Now depends on Kombu 2.5.15.

  • Now depends on billiard version

  • AMQP Result backend: No longer caches queue declarations.

    The queues created by the AMQP result backend are always unique, so caching the declarations caused a slow memory leak.

  • Worker: Fixed crash when hostname contained Unicode characters.

    Contributed by Daodao.

  • The worker would no longer start if the -P solo pool was selected (Issue #1548).

  • Redis/Cache result backends would not complete chords if any of the tasks were retried (Issue #1401).

  • Task decorator is no longer lazy if app is finalized.

  • AsyncResult: Fixed bug with copy(AsyncResult) when no current_app available.

  • ResultSet: Now properly propagates app when passed string id’s.

  • Loader now ignores CELERY_CONFIG_MODULE if value is empty string.

  • Fixed race condition in Proxy object where it tried to delete an attribute twice, resulting in AttributeError.

  • Task methods now works with the CELERY_ALWAYS_EAGER setting (Issue #1478).

  • Broadcast queues were accidentally declared when publishing tasks (Issue #1540).

  • New C_FAKEFORK environment variable can be used to debug the init scripts.

    Setting this will skip the daemonization step so that errors printed to stderr after standard outs are closed can be seen:

    $ C_FAKEFORK /etc/init.d/celeryd start

    This works with the celery multi command in general.

  • get_pickleable_etype did not always return a value (Issue #1556).

  • Fixed bug where app.GroupResult.restore would fall back to the default app.

  • Fixed rare bug where built-in tasks would use the current_app.

  • maybe_fileno() now handles ValueError.


release-date:2013-09-02 01:00 P.M BST
release-by:Ask Solem
  • Now depends on Kombu 2.5.14.

  • send_task did not honor link and link_error arguments.

    This had the side effect of chains not calling unregistered tasks, silently discarding them.

    Fix contributed by Taylor Nelson.

  • celery.state: Optimized precedence lookup.

    Contributed by Matt Robenolt.

  • Posix: Daemonization did not redirect sys.stdin to /dev/null.

    Fix contributed by Alexander Smirnov.

  • Canvas: group bug caused fallback to default app when .apply_async used (Issue #1516)

  • Canvas: generator arguments was not always pickleable.


release-date:2013-08-16 04:30 P.M BST
release-by:Ask Solem
  • Now depends on Kombu 2.5.13.

  • Now depends on billiard

  • Fixed bug with monthly and yearly crontabs (Issue #1465).

    Fix contributed by Guillaume Gauvrit.

  • Fixed memory leak caused by time limits (Issue #1129, Issue #1427)

  • Worker will now sleep if being restarted more than 5 times in one second to avoid spamming with worker-online events.

  • Includes documentation fixes

    Contributed by: Ken Fromm, Andreas Savvides, Alex Kiriukha, Michael Fladischer.


release-date:2013-07-05 04:30 P.M BST
release-by:Ask Solem
  • Now depends on billiard

    This version fixed a bug when running without the billiard C extension.

  • 3.0.20 broke eventlet/gevent support (worker not starting).

  • Fixed memory leak problem when MongoDB result backend was used with the gevent pool.

    Fix contributed by Ross Lawley.


release-date:2013-06-28 04:00 P.M BST
release-by:Ask Solem
  • Contains workaround for deadlock problems.

    A better solution will be part of Celery 3.1.

  • Now depends on Kombu 2.5.12.

  • Now depends on billiard

  • --loader argument no longer supported importing loaders from the current directory.

  • [Worker] Fixed memory leak when restarting after connection lost (Issue #1325).

  • [Worker] Fixed UnicodeDecodeError at startup (Issue #1373).

    Fix contributed by Jessica Tallon.

  • [Worker] Now properly rewrites unpickleable exceptions again.

  • Fixed possible race condition when evicting items from the revoked task set.

  • [generic-init.d] Fixed compatibility with Ubuntu’s minimal Dash shell (Issue #1387).

    Fix contributed by monkut.

  • Task.apply/ALWAYS_EAGER now also executes callbacks and errbacks (Issue #1336).

  • [Worker] The worker-shutdown signal was no longer being dispatched (Issue #1339)j

  • [Python 3] Fixed problem with threading.Event.

    Fix contributed by Xavier Ordoquy.

  • [Python 3] Now handles io.UnsupportedOperation that may be raised by file.fileno() in Python 3.

  • [Python 3] Fixed problem with qualname.

  • [events.State] Now ignores unknown event-groups.

  • [MongoDB backend] No longer uses deprecated safe parameter.

    Fix contributed by rfkrocktk

  • The eventlet pool now imports on Windows.

  • [Canvas] Fixed regression where immutable chord members may receive arguments (Issue #1340).

    Fix contributed by Peter Brook.

  • [Canvas] chain now accepts generator argument again (Issue #1319).

  • celery.migrate command now consumes from all queues if no queues specified.

    Fix contributed by John Watson.


release-date:2013-04-17 04:30:00 P.M BST
release-by:Ask Solem
  • Now depends on billiard

  • A Python 3 related fix managed to disable the deadlock fix announced in 3.0.18.

    Tests have been added to make sure this does not happen again.

  • Task retry policy: Default max_retries is now 3.

    This ensures clients will not be hanging while the broker is down.


    You can set a longer retry for the worker by using the celeryd_after_setup signal:

    from celery.signals import celeryd_after_setup
    def configure_worker(instance, conf, **kwargs):
            'max_retries': 100,
            'interval_start': 0,
            'interval_max': 1,
            'interval_step': 0.2,
  • Worker: Will now properly display message body in error messages even if the body is a buffer instance.

  • 3.0.18 broke the MongoDB result backend (Issue #1303).


release-date:2013-04-12 05:00:00 P.M BST
release-by:Ask Solem
  • Now depends on kombu 2.5.10.

    See the kombu changelog.

  • Now depends on billiard

  • Can now specify a whitelist of accepted serializers using the new CELERY_ACCEPT_CONTENT setting.

    This means that you can force the worker to discard messages serialized with pickle and other untrusted serializers. For example to only allow JSON serialized messages use:


    you can also specify MIME types in the whitelist:

    CELERY_ACCEPT_CONTENT = ['application/json']
  • Fixed deadlock in multiprocessing’s pool caused by the semaphore not being released when terminated by signal.

  • Processes Pool: It’s now possible to debug pool processes using GDB.

  • celery report now censors possibly secret settings, like passwords and secret tokens.

    You should still check the output before pasting anything on the internet.

  • Connection URLs now ignore multiple ‘+’ tokens.

  • Worker/statedb: Now uses pickle protocol 2 (Py2.5+)

  • Fixed Python 3 compatibility issues.

  • Worker: A warning is now given if a worker is started with the same node name as an existing worker.

  • Worker: Fixed a deadlock that could occur while revoking tasks (Issue #1297).

  • Worker: The HUP handler now closes all open file descriptors before restarting to ensure file descriptors does not leak (Issue #1270).

  • Worker: Optimized storing/loading the revoked tasks list (Issue #1289).

    After this change the --statedb file will take up more disk space, but loading from and storing the revoked tasks will be considerably faster (what before took 5 minutes will now take less than a second).

  • Celery will now suggest alternatives if there’s a typo in the broker transport name (e.g. ampq -> amqp).

  • Worker: The auto-reloader would cause a crash if a monitored file was unlinked.

    Fix contributed by Agris Ameriks.

  • Fixed AsyncResult pickling error.

    Fix contributed by Thomas Minor.

  • Fixed handling of Unicode in logging output when using log colors (Issue #427).

  • ConfigurationView is now a MutableMapping.

    Contributed by Aaron Harnly.

  • Fixed memory leak in LRU cache implementation.

    Fix contributed by Romuald Brunet.

  • celery.contrib.rdb: Now works when sockets are in non-blocking mode.

    Fix contributed by Theo Spears.

  • The inspect reserved remote control command included active (started) tasks with the reserved tasks (Issue #1030).

  • The task_failure signal received a modified traceback object meant for pickling purposes, this has been fixed so that it now receives the real traceback instead.

  • The @task decorator silently ignored positional arguments, it now raises the expected TypeError instead (Issue #1125).

  • The worker will now properly handle messages with invalid eta/expires fields (Issue #1232).

  • The pool_restart remote control command now reports an error if the CELERYD_POOL_RESTARTS setting is not set.

  • celery.conf.add_defaults can now be used with non-dict objects.

  • Fixed compatibility problems in the Proxy class (Issue #1087).

    The class attributes __module__, __name__ and __doc__ are now meaningful string objects.

    Thanks to Marius Gedminas.

  • MongoDB Backend: The MONGODB_BACKEND_SETTINGS setting now accepts a option key that lets you forward arbitrary kwargs to the underlying pymongo.Connection object (Issue #1015).

  • Beat: The daily backend cleanup task is no longer enabled for result backends that support automatic result expiration (Issue #1031).

  • Canvas list operations now takes application instance from the first task in the list, instead of depending on the current_app (Issue #1249).

  • Worker: Message decoding error log message now includes traceback information.

  • Worker: The startup banner now includes system platform.

  • celery inspect|status|control now gives an error if used with an SQL based broker transport.


release-date:2013-03-22 04:00:00 P.M UTC
release-by:Ask Solem
  • Now depends on kombu 2.5.8

  • Now depends on billiard

  • RabbitMQ/Redis: thread-less and lock-free rate-limit implementation.

    This means that rate limits pose minimal overhead when used with RabbitMQ/Redis or future transports using the eventloop, and that the rate-limit implementation is now thread-less and lock-free.

    The thread-based transports will still use the old implementation for now, but the plan is to use the timer also for other broker transports in Celery 3.1.

  • Rate limits now works with eventlet/gevent if using RabbitMQ/Redis as the broker.

  • A regression caused task.retry to ignore additional keyword arguments.

    Extra keyword arguments are now used as execution options again. Fix contributed by Simon Engledew.

  • Windows: Fixed problem with the worker trying to pickle the Django settings module at worker startup.

  • generic-init.d: No longer double quotes $CELERYD_CHDIR (Issue #1235).

  • generic-init.d: Removes bash-specific syntax.

    Fix contributed by Pär Wieslander.

  • Cassandra Result Backend: Now handles the AllServersUnavailable error (Issue #1010).

    Fix contributed by Jared Biel.

  • Result: Now properly forwards apps to GroupResults when deserializing (Issue #1249).

    Fix contributed by Charles-Axel Dein.

  • GroupResult.revoke now supports the terminate and signal keyword arguments.

  • Worker: Multiprocessing pool workers now import task modules/configuration before setting up the logging system so that logging signals can be connected before they’re dispatched.

  • chord: The AsyncResult instance returned now has its parent attribute set to the header GroupResult.

    This is consistent with how chain works.


release-date:2013-03-07 04:00:00 P.M UTC
release-by:Ask Solem
  • Happy International Women’s Day!

    We have a long way to go, so this is a chance for you to get involved in one of the organizations working for making our communities more diverse.

  • Now depends on kombu version 2.5.7

  • Now depends on billiard version

  • AMQP heartbeats are now disabled by default.

    Some users experiences issues with heartbeats enabled, and it’s not strictly necessary to use them.

    If you’re experiencing problems detecting connection failures, you can re-enable heartbeats by configuring the BROKER_HEARTBEAT setting.

  • Worker: Now propagates connection errors occurring in multiprocessing callbacks, so that the connection can be reset (Issue #1226).

  • Worker: Now propagates connection errors occurring in timer callbacks, so that the connection can be reset.

  • The modules in CELERY_IMPORTS and CELERY_INCLUDE are now imported in the original order (Issue #1161).

    The modules in CELERY_IMPORTS will be imported first, then continued by CELERY_INCLUDE.

    Thanks to Joey Wilhelm.

  • New bash completion for celery available in the git repository:

    You can source this file or put it in bash_completion.d to get auto-completion for the celery command-line utility.

  • The node name of a worker can now include unicode characters (Issue #1186).

  • The repr of a crontab object now displays correctly (Issue #972).

  • events.State no longer modifies the original event dictionary.

  • No longer uses Logger.warn deprecated in Python 3.

  • Cache Backend: Now works with chords again (Issue #1094).

  • Chord unlock now handles errors occurring while calling the callback.

  • Generic worker init.d script: Status check is now performed by querying the pid of the instance instead of sending messages.

    Contributed by Milen Pavlov.

  • Improved init scripts for CentOS.

    • Updated to support celery 3.x conventions.
    • Now uses CentOS built-in status and killproc
    • Support for multi-node / multi-pid worker services.
    • Standard color-coded CentOS service-init output.
    • A test suite.

    Contributed by Milen Pavlov.

  • ResultSet.join now always works with empty result set (Issue #1219).

  • A group consisting of a single task is now supported (Issue #1219).

  • Now supports the pycallgraph program (Issue #1051).

  • Fixed Jython compatibility problems.

  • Django tutorial: Now mentions that the example app must be added to INSTALLED_APPS (Issue #1192).


release-date:2013-02-11 04:30:00 P.M UTC
release-by:Ask Solem


release-date:2013-02-08 05:00:00 P.M UTC
release-by:Ask Solem
  • Now depends on Kombu 2.5.6

  • Now depends on billiard

  • execv is now disabled by default.

    It was causing too many problems for users, you can still enable it using the CELERYD_FORCE_EXECV setting.

    execv was only enabled when transports other than amqp/redis was used, and it’s there to prevent deadlocks caused by mutexes not being released before the process forks. Unfortunately it also changes the environment introducing many corner case bugs that is hard to fix without adding horrible hacks. Deadlock issues are reported far less often than the bugs that execv are causing, so we now disable it by default.

    Work is in motion to create non-blocking versions of these transports so that execv is not necessary (which is the situation with the amqp and redis broker transports)

  • Chord exception behavior defined (Issue #1172).

    From Celery 3.1 the chord callback will change state to FAILURE when a task part of a chord raises an exception.

    It was never documented what happens in this case, and the actual behavior was very unsatisfactory, indeed it will just forward the exception value to the chord callback.

    For backward compatibility reasons we do not change to the new behavior in a bugfix release, even if the current behavior was never documented. Instead you can enable the CELERY_CHORD_PROPAGATES setting to get the new behavior that will be default from Celery 3.1.

    See more at Error handling.

  • worker: Fixes bug with ignored and retried tasks.

    The on_chord_part_return and Task.after_return callbacks, nor the task_postrun signal should be called when the task was retried/ignored.

    Fix contributed by Vlad.

  • GroupResult.join_native now respects the propagate argument.

  • added as an alias to subtask['options'].id

    >>> s = add.s(2, 2)
    >>> = 'my-id'
    >>> s['options']
    {'task_id': 'my-id'}
  • worker: Fixed error Could not start worker processes occurring when restarting after connection failure (Issue #1118).

  • Adds new signal task-retried (Issue #1169).

  • celery events –dumper now handles connection loss.

  • Will now retry sending the task-sent event in case of connection failure.

  • amqp backend: Now uses Message.requeue instead of republishing the message after poll.

  • New BROKER_HEARTBEAT_CHECKRATE setting introduced to modify the rate at which broker connection heartbeats are monitored.

    The default value was also changed from 3.0 to 2.0.

  • is now pickleable.

    Fix contributed by Mher Movsisyan.

  • celery.datastructures.LRUCache is now pickleable.

    Fix contributed by Mher Movsisyan.

  • The stats broadcast command now includes the workers pid.

    Contributed by Mher Movsisyan.

  • New conf remote control command to get a workers current configuration.

    Contributed by Mher Movsisyan.

  • Adds the ability to modify the chord unlock task’s countdown argument (Issue #1146).

    Contributed by Jun Sakai

  • beat: The scheduler now uses the now()` method of the schedule, so that schedules can provide a custom way to get the current date and time.

    Contributed by Raphaël Slinckx

  • Fixed pickling of configuration modules on Windows or when execv is used (Issue #1126).

  • Multiprocessing logger is now configured with loglevel ERROR by default.

    Since 3.0 the multiprocessing loggers were disabled by default (only configured when the MP_LOG environment variable was set).


release-date:2013-01-07 04:00:00 P.M UTC
release-by:Ask Solem
  • Now depends on Kombu 2.5

    • py-amqp has replaced amqplib as the default transport, gaining support for AMQP 0.9, and the RabbitMQ extensions including Consumer Cancel Notifications and heartbeats.
    • support for multiple connection URLs for failover.
    • Read more in the Kombu 2.5 changelog.
  • Now depends on billiard

  • Fixed a deadlock issue that could occur when the producer pool inherited the connection pool instance of the parent process.

  • The --loader option now works again (Issue #1066).

  • celery umbrella command: All subcommands now supports the --workdir option (Issue #1063).

  • Groups included in chains now give GroupResults (Issue #1057)

    Previously it would incorrectly add a regular result instead of a group result, but now this works:

    # [4 + 4, 4 + 8, 16 + 8]
    >>> res = (add.s(2, 2) | group(add.s(4), add.s(8), add.s(16)))()
    >>> res
    <GroupResult: a0acf905-c704-499e-b03a-8d445e6398f7 [
  • Chains can now chain other chains and use partial arguments (Issue #1057).


    >>> c1 = (add.s(2) | add.s(4))
    >>> c2 = (add.s(8) | add.s(16))
    >>> c3 = (c1 | c2)
    # 8 + 2 + 4 + 8 + 16
    >>> assert c3(8).get() == 38
  • Subtasks can now be used with unregistered tasks.

    You can specify subtasks even if you just have the name:

    >>> s = subtask(task_name, args=(), kwargs=())
    >>> s.delay()
  • The celery shell command now always adds the current directory to the module path.

  • The worker will now properly handle the pytz.AmbiguousTimeError exception raised when an ETA/countdown is prepared while being in DST transition (Issue #1061).

  • force_execv: Now makes sure that task symbols in the original task modules will always use the correct app instance (Issue #1072).

  • AMQP Backend: Now republishes result messages that have been polled (using result.ready() and friends, result.get() will not do this in this version).

  • Crontab schedule values can now “wrap around”

    This means that values like 11-1 translates to [11, 12, 1].

    Contributed by Loren Abrams.

  • multi stopwait command now shows the pid of processes.

    Contributed by Loren Abrams.

  • Handling of ETA/countdown fixed when the CELERY_ENABLE_UTC

    setting is disabled (Issue #1065).

  • A number of uneeded properties were included in messages, caused by accidentally passing Queue.as_dict as message properties.

  • Rate limit values can now be float

    This also extends the string format so that values like "0.5/s" works.

    Contributed by Christoph Krybus

  • Fixed a typo in the broadcast routing documentation (Issue #1026).

  • Rewrote confusing section about idempotence in the task user guide.

  • Fixed typo in the daemonization tutorial (Issue #1055).

  • Fixed several typos in the documentation.

    Contributed by Marius Gedminas.

  • Batches: Now works when using the eventlet pool.

    Fix contributed by Thomas Grainger.

  • Batches: Added example sending results to celery.contrib.batches.

    Contributed by Thomas Grainger.

  • Mongodb backend: Connection max_pool_size can now be set in CELERY_MONGODB_BACKEND_SETTINGS.

    Contributed by Craig Younkins.

  • Fixed problem when using earlier versions of pytz.

    Fix contributed by Vlad.

  • Docs updated to include the default value for the CELERY_TASK_RESULT_EXPIRES setting.

  • Improvements to the django-celery tutorial.

    Contributed by Locker537.

  • The add_consumer control command did not properly persist the addition of new queues so that they survived connection failure (Issue #1079).


release-date:2012-11-06 02:00 P.M UTC
release-by:Ask Solem
  • Now depends on kombu 2.4.8

    • [Redis] New and improved fair queue cycle algorithm (Kevin McCarthy).

    • [Redis] Now uses a Redis-based mutex when restoring messages.

    • [Redis] Number of messages that can be restored in one interval is no

      longer limited (but can be set using the unacked_restore_limit transport option.)

    • Heartbeat value can be specified in broker URLs (Mher Movsisyan).

    • Fixed problem with msgpack on Python 3 (Jasper Bryant-Greene).

  • Now depends on billiard

  • Celery can now be used with static analysis tools like PyDev/PyCharm/pylint etc.

  • Development documentation has moved to Read The Docs.

  • New CELERY_QUEUE_HA_POLICY setting used to set the default HA policy for queues when using RabbitMQ.

  • New method Task.subtask_from_request returns a subtask using the current request.

  • Results get_many method did not respect timeout argument.

    Fix contributed by Remigiusz Modrzejewski

  • generic_init.d scripts now support setting CELERY_CREATE_DIRS to always create log and pid directories (Issue #1045).

    This can be set in your /etc/default/celeryd.

  • Fixed strange kombu import problem on Python 3.2 (Issue #1034).

  • Worker: ETA scheduler now uses millisecond precision (Issue #1040).

  • The --config argument to programs is now supported by all loaders.

  • The CASSANDRA_OPTIONS setting has now been documented.

    Contributed by Jared Biel.

  • Task methods (celery.contrib.methods) cannot be used with the old task base class, the task decorator in that module now inherits from the new.

  • An optimization was too eager and caused some logging messages to never emit.

  • celery.contrib.batches now works again.

  • Fixed missing whitespace in bdist_rpm requirements (Issue #1046).

  • Event state’s tasks_by_name applied limit before filtering by name.

    Fix contributed by Alexander A. Sosnovskiy.


release-date:2012-09-26 04:00 P.M UTC
release-by:Ask Solem
  • [security:low] generic-init.d scripts changed permissions of /var/log & /var/run

    In the daemonization tutorial the recommended directories were as follows:


    But in the scripts themselves the default files were /var/log/celery%n.log and /var/run/, so if the user did not change the location by configuration, the directories /var/log and /var/run would be created - and worse have their permissions and owners changed.

    This change means that:

    • Default pid file is /var/run/celery/
    • Default log file is /var/log/celery/%n.log
    • The directories are only created and have their permissions changed if no custom locations are set.

    Users can force paths to be created by calling the create-paths subcommand:

    $ sudo /etc/init.d/celeryd create-paths

    Upgrading Celery will not update init scripts

    To update the init scripts you have to re-download the files from source control and update them manually. You can find the init scripts for version 3.0.x at:

  • Now depends on billiard

  • Fixes request stack protection when app is initialized more than once (Issue #1003).

  • ETA tasks now properly works when system timezone is not the same as the configured timezone (Issue #1004).

  • Terminating a task now works if the task has been sent to the pool but not yet acknowledged by a pool process (Issue #1007).

    Fix contributed by Alexey Zatelepin

  • Terminating a task now properly updates the state of the task to revoked, and sends a task-revoked event.

  • Generic worker init script now waits for workers to shutdown by default.

  • Multi: No longer parses –app option (Issue #1008).

  • Multi: stop_verify command renamed to stopwait.

  • Daemonization: Now delays trying to create pidfile/logfile until after the working directory has been changed into.

  • celery worker and celery beat commands now respects the --no-color option (Issue #999).

  • Fixed typos in eventlet examples (Issue #1000)

    Fix contributed by Bryan Bishop. Congratulations on opening bug #1000!

  • Tasks that raise Ignore are now acknowledged.

  • Beat: Now shows the name of the entry in sending due task logs.


release-date:2012-09-20 05:30 P.M BST
release-by:Ask Solem
  • Now depends on kombu 2.4.7

  • Now depends on billiard

    • Fixes crash at startup when using Django and pre-1.4 projects (setup_environ).

    • Hard time limits now sends the KILL signal shortly after TERM, to terminate processes that have signal handlers blocked by C extensions.

    • Billiard now installs even if the C extension cannot be built.

      It’s still recommended to build the C extension if you are using a transport other than rabbitmq/redis (or use forced execv for some other reason).

    • Pool now sets a current_process().index attribute that can be used to create as many log files as there are processes in the pool.

  • Canvas: chord/group/chain no longer modifies the state when called

    Previously calling a chord/group/chain would modify the ids of subtasks so that:

    >>> c = chord([add.s(2, 2), add.s(4, 4)], xsum.s())
    >>> c()
    >>> c() <-- call again

    at the second time the ids for the tasks would be the same as in the previous invocation. This is now fixed, so that calling a subtask won’t mutate any options.

  • Canvas: Chaining a chord to another task now works (Issue #965).

  • Worker: Fixed a bug where the request stack could be corrupted if relative imports are used.

    Problem usually manifested itself as an exception while trying to send a failed task result (NoneType does not have id attribute).

    Fix contributed by Sam Cooke.

  • Tasks can now raise Ignore to skip updating states or events after return.


    from celery.exceptions import Ignore
    def custom_revokes():
        if redis.sismember('tasks.revoked',
            raise Ignore()
  • The worker now makes sure the request/task stacks are not modified by the initial Task.__call__.

    This would previously be a problem if a custom task class defined __call__ and also called super().

  • Because of problems the fast local optimization has been disabled, and can only be enabled by setting the USE_FAST_LOCALS attribute.

  • Worker: Now sets a default socket timeout of 5 seconds at shutdown so that broken socket reads do not hinder proper shutdown (Issue #975).

  • More fixes related to late eventlet/gevent patching.

  • Documentation for settings out of sync with reality:


      Documented as disabled by default, but it was enabled by default since 2.5 as stated by the 2.5 changelog.


      The default max_retries had been set to 100, but documented as being 3, and the interval_max was set to 1 but documented as 0.2. The default setting are now set to 3 and 0.2 as it was originally documented.

    Fix contributed by Matt Long.

  • Worker: Log messages when connection established and lost have been improved.

  • The repr of a crontab schedule value of ‘0’ should be ‘*’ (Issue #972).

  • Revoked tasks are now removed from reserved/active state in the worker (Issue #969)

    Fix contributed by Alexey Zatelepin.

  • gevent: Now supports hard time limits using gevent.Timeout.

  • Documentation: Links to init scripts now point to the 3.0 branch instead of the development branch (master).

  • Documentation: Fixed typo in signals user guide (Issue #986). ->

  • Eventlet/gevent: The worker did not properly set the custom app for new greenlets.

  • Eventlet/gevent: Fixed a bug where the worker could not recover from connection loss (Issue #959).

    Also, because of a suspected bug in gevent the BROKER_CONNECTION_TIMEOUT setting has been disabled when using gevent


release-date:2012-08-31 06:00 P.M BST
release-by:Ask Solem
  • Important note for users of Django and the database scheduler!

    Recently a timezone issue has been fixed for periodic tasks, but erroneous timezones could have already been stored in the database, so for the fix to work you need to reset the last_run_at fields.

    You can do this by executing the following command:

    $ python shell
    >>> from djcelery.models import PeriodicTask
    >>> PeriodicTask.objects.update(last_run_at=None)

    You also have to do this if you change the timezone or CELERY_ENABLE_UTC setting.

  • Note about the CELERY_ENABLE_UTC setting.

    If you previously disabled this just to force periodic tasks to work with your timezone, then you are now encouraged to re-enable it.

  • Now depends on Kombu 2.4.5 which fixes PyPy + Jython installation.

  • Fixed bug with timezones when CELERY_ENABLE_UTC is disabled (Issue #952).

  • Fixed a typo in the celerybeat upgrade mechanism (Issue #951).

  • Make sure the exc_info argument to logging is resolved (Issue #899).

  • Fixed problem with Python 3.2 and thread join timeout overflow (Issue #796).

  • A test case was occasionally broken for Python 2.5.

  • Unit test suite now passes for PyPy 1.9.

  • App instances now supports the with statement.

    This calls the new close() method at exit, which cleans up after the app like closing pool connections.

    Note that this is only necessary when dynamically creating apps, e.g. for “temporary” apps.

  • Support for piping a subtask to a chain.

    For example:

    pipe = sometask.s() | othertask.s()
    new_pipe = mytask.s() | pipe

    Contributed by Steve Morin.

  • Fixed problem with group results on non-pickle serializers.

    Fix contributed by Steeve Morin.


release-date:2012-08-29 05:00 P.M BST
release-by:Ask Solem
  • Now depends on Kombu 2.4.4

  • Fixed problem with amqplib and receiving larger message payloads (Issue #922).

    The problem would manifest itself as either the worker hanging, or occasionally a Framing error exception appearing.

    Users of the new pyamqp:// transport must upgrade to amqp 0.9.3.

  • Beat: Fixed another timezone bug with interval and crontab schedules (Issue #943).

  • Beat: The schedule file is now automatically cleared if the timezone is changed.

    The schedule is also cleared when you upgrade to 3.0.8 from an earlier version, this to register the initial timezone info.

  • Events: The worker-heartbeat event now include processed and active count fields.

    Contributed by Mher Movsisyan.

  • Fixed error with error email and new task classes (Issue #931).

  • BaseTask.__call__ is no longer optimized away if it has been monkey patched.

  • Fixed shutdown issue when using gevent (Issue #911 & Issue #936).

    Fix contributed by Thomas Meson.


release-date:2012-08-24 05:00 P.M BST
release-by:Ask Solem
  • Fixes several problems with periodic tasks and timezones (Issue #937).

  • Now depends on kombu 2.4.2

    • Redis: Fixes a race condition crash
    • Fixes an infinite loop that could happen when retrying establishing the broker connection.
  • Daemons now redirect standard file descriptors to /dev/null

    Though by default the standard outs are also redirected to the logger instead, but you can disable this by changing the CELERY_REDIRECT_STDOUTS setting.

  • Fixes possible problems when eventlet/gevent is patched too late.

  • LoggingProxy no longer defines fileno() (Issue #928).

  • Results are now ignored for the chord unlock task.

    Fix contributed by Steeve Morin.

  • Cassandra backend now works if result expiry is disabled.

    Fix contributed by Steeve Morin.

  • The traceback object is now passed to signal handlers instead of the string representation.

    Fix contributed by Adam DePue.

  • Celery command: Extensions are now sorted by name.

  • A regression caused the task-failed event to be sent with the exception object instead of its string representation.

  • The worker daemon would try to create the pid file before daemonizing to catch errors, but this file was not immediately released (Issue #923).

  • Fixes Jython compatibility.

  • billiard.forking_enable was called by all pools not just the processes pool, which would result in a useless warning if the billiard C extensions were not installed.


release-date:2012-08-17 11:00 P.M BST
release-by:Ask Solem
  • Now depends on kombu 2.4.0

  • Now depends on billiard

  • Redis: Celery now tries to restore messages whenever there are no messages in the queue.

  • Crontab schedules now properly respects CELERY_TIMEZONE setting.

    It’s important to note that crontab schedules uses UTC time by default unless this setting is set.

    Issue #904 and django-celery #150.

  • billiard.enable_forking is now only set by the processes pool.

  • The transport is now properly shown by celery report (Issue #913).

  • The –app argument now works if the last part is a module name (Issue #921).

  • Fixed problem with unpickleable exceptions (billiard #12).

  • Adds task_name attribute to EagerResult which is always None (Issue #907).

  • Old Task class in celery.task no longer accepts magic kwargs by default (Issue #918).

    A regression long ago disabled magic kwargs for these, and since no one has complained about it we don’t have any incentive to fix it now.

  • The inspect reserved control command did not work properly.

  • Should now play better with static analyzation tools by explicitly specifying dynamically created attributes in the celery and celery.task modules.

  • Terminating a task now results in RevokedTaskError instead of a WorkerLostError.

  • AsyncResult.revoke now accepts terminate and signal arguments.

  • The task-revoked event now includes new fields: terminated, signum, and expired.

  • The argument to TaskRevokedError is now one of the reasons revoked, expired or terminated.

  • Old Task class does no longer use classmethods for push_request and pop_request (Issue #912).

  • GroupResult now supports the children attribute (Issue #916).

  • AsyncResult.collect now respects the intermediate argument (Issue #917).

  • Fixes example task in documentation (Issue #902).

  • Eventlet fixed so that the environment is patched as soon as possible.

  • eventlet: Now warns if celery related modules that depends on threads are imported before eventlet is patched.

  • Improved event and camera examples in the monitoring guide.

  • Disables celery command setuptools entrypoints if the command can’t be loaded.

  • Fixed broken dump_request example in the tasks guide.


release-date:2012-08-01 04:00 P.M BST
release-by:Ask Solem
  • Now depends on kombu 2.3.1 + billiard

  • Fixed a bug with the -B option (cannot pickle thread.lock objects) (Issue #894 + Issue #892, + django-celery #154).

  • The restart_pool control command now requires the CELERYD_POOL_RESTARTS setting to be enabled

    This change was necessary as the multiprocessing event that the restart command depends on is responsible for creating many semaphores/file descriptors, resulting in problems in some environments.

  • chain.apply now passes args to the first task (Issue #889).

  • Documented previously secret options to the Django-Celery monitor in the monitoring userguide (Issue #396).

  • Old changelog are now organized in separate documents for each series, see History.


release-date:2012-07-26 07:00 P.M BST
release-by:Ask Solem
  • Now depends on Kombu 2.3

  • New experimental standalone Celery monitor: Flower

    See Flower: Real-time Celery web-monitor to read more about it!

    Contributed by Mher Movsisyan.

  • Now supports AMQP heartbeats if using the new pyamqp:// transport.

    • The py-amqp transport requires the amqp library to be installed:

      $ pip install amqp
    • Then you need to set the transport URL prefix to pyamqp://.

    • The default heartbeat value is 10 seconds, but this can be changed using the BROKER_HEARTBEAT setting:

    • If the broker heartbeat is set to 10 seconds, the heartbeats will be monitored every 5 seconds (double the hertbeat rate).

    See the Kombu 2.3 changelog for more information.

  • Now supports RabbitMQ Consumer Cancel Notifications, using the pyamqp:// transport.

    This is essential when running RabbitMQ in a cluster.

    See the Kombu 2.3 changelog for more information.

  • Delivery info is no longer passed directly through.

    It was discovered that the SQS transport adds objects that can’t be pickled to the delivery info mapping, so we had to go back to using the whitelist again.

    Fixing this bug also means that the SQS transport is now working again.

  • The semaphore was not properly released when a task was revoked (Issue #877).

    This could lead to tasks being swallowed and not released until a worker restart.

    Thanks to Hynek Schlawack for debugging the issue.

  • Retrying a task now also forwards any linked tasks.

    This means that if a task is part of a chain (or linked in some other way) and that even if the task is retried, then the next task in the chain will be executed when the retry succeeds.

  • Chords: Now supports setting the interval and other keyword arguments to the chord unlock task.

    • The interval can now be set as part of the chord subtasks kwargs:

      chord(header)(body, interval=10.0)
    • In addition the chord unlock task now honors the Task.default_retry_delay option, used when none is specified, which also means that the default interval can also be changed using annotations:

          'celery.chord_unlock': {
              'default_retry_delay': 10.0,
  • New Celery.add_defaults() method can add new default configuration dicts to the applications configuration.

    For example:

    config = {'FOO': 10}

    is the same as celery.conf.update(config) except that data will not be copied, and that it will not be pickled when the worker spawns child processes.

    In addition the method accepts a callable:

    def initialize_config():
        # insert heavy stuff that can't be done at import time here.

    which means the same as the above except that it will not happen until the celery configuration is actually used.

    As an example, Celery can lazily use the configuration of a Flask app:

    flask_app = Flask()
    celery = Celery()
    celery.add_defaults(lambda: flask_app.config)
  • Revoked tasks were not marked as revoked in the result backend (Issue #871).

    Fix contributed by Hynek Schlawack.

  • Eventloop now properly handles the case when the epoll poller object has been closed (Issue #882).

  • Fixed syntax error in funtests/

    Fix contributed by Catalin Iacob.

  • group/chunks: Now accepts empty task list (Issue #873).

  • New method names:

    The old names still work for backward compatibility.


release-date:2012-07-20 09:17 P.M BST
release-by:Ask Solem
  • amqplib passes the channel object as part of the delivery_info and it’s not pickleable, so we now remove it.


release-date:2012-07-20 04:00 P.M BST
release-by:Ask Solem
  • A bug caused the following task options to not take defaults from the

    configuration (Issue #867 + Issue #858)

    The following settings were affected:

    Fix contributed by John Watson.

  • Task Request: delivery_info is now passed through as-is (Issue #807).

  • The eta argument now supports datetime’s with a timezone set (Issue #855).

  • The worker’s banner displayed the autoscale settings in the wrong order (Issue #859).

  • Extension commands are now loaded after concurrency is set up so that they don’t interfere with e.g. eventlet patching.

  • Fixed bug in the threaded pool (Issue #863)

  • The task failure handler mixed up the fields in sys.exc_info().

    Fix contributed by Rinat Shigapov.

  • Fixed typos and wording in the docs.

    Fix contributed by Paul McMillan


    If enabled each worker will consume from their own dedicated queue which can be used to route tasks to specific workers.

  • Fixed several edge case bugs in the add consumer remote control command.

  • migrate: Can now filter and move tasks to specific workers if CELERY_WORKER_DIRECT is enabled.

    Among other improvements, the following functions have been added:

    • move_direct(filterfun, **opts)
    • move_direct_by_id(task_id, worker_hostname, **opts)
    • move_direct_by_idmap({task_id: worker_hostname, ...}, **opts)
    • move_direct_by_taskmap({task_name: worker_hostname, ...}, **opts)
  • default_connection() now accepts a pool argument that if set to false causes a new connection to be created instead of acquiring one from the pool.

  • New signal: celeryd_after_setup.

  • Default loader now keeps lowercase attributes from the configuration module.


release-date:2012-07-10 06:00 P.M BST
release-by:Ask Solem
  • Now depends on kombu 2.2.5

  • inspect now supports limit argument:

  • Beat: now works with timezone aware datetime’s.

  • Task classes inheriting from celery import Task mistakingly enabled accept_magic_kwargs.

  • Fixed bug in inspect scheduled (Issue #829).

  • Beat: Now resets the schedule to upgrade to UTC.

  • The celery worker command now works with eventlet/gevent.

    Previously it would not patch the environment early enough.

  • The celery command now supports extension commands using setuptools entry-points.

    Libraries can add additional commands to the celery command by adding an entry-point like:

            'celery.commands': [
                'foo = my.module:Command',

    The command must then support the interface of celery.bin.base.Command.

  • contrib.migrate: New utilities to move tasks from one queue to another.

  • The task-sent event now contains exchange and routing_key fields.

  • Fixes bug with installing on Python 3.

    Fix contributed by Jed Smith.

3.0.0 (Chiastic Slide)

release-date:2012-07-07 01:30 P.M BST
release-by:Ask Solem

See What’s new in Celery 3.0 (Chiastic Slide).

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