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

Change history for Celery 2.3


release-date:2011-11-25 04:00 P.M GMT
release-by:Ask Solem

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.


  • Backported fix for #455 from 2.4 to 2.3.
  • Statedb was not saved at shutdown.
  • Fixes worker sometimes hanging when hard time limit exceeded.


release-date:2011-16-09 05:00 P.M BST
release-by:Mher Movsisyan
  • Monkey patching sys.stdout could result in the worker crashing if the replacing object did not define isatty() (Issue #477).
  • CELERYD option in /etc/default/celeryd should not be used with generic init scripts.


release-date:2011-10-07 05:00 P.M BST
release-by:Ask Solem


  • Improved Contributing guide.

    If you’d like to contribute to Celery you should read the Contributing Gudie.

    We are looking for contributors at all skill levels, so don’t hesitate!

  • Now depends on Kombu 1.3.1

  • Task.request now contains the current worker host name (Issue #460).

    Available as task.request.hostname.

  • It is now easier for app subclasses to extend how they are pickled.



  • purge/discard_all was not working correctly (Issue #455).

  • The coloring of log messages didn’t handle non-ASCII data well (Issue #427).

  • [Windows] the multiprocessing pool tried to import os.kill even though this is not available there (Issue #450).

  • Fixes case where the worker could become unresponsive because of tasks exceeding the hard time limit.

  • The task-sent event was missing from the event reference.

  • ResultSet.iterate now returns results as they finish (Issue #459).

    This was not the case previously, even though the documentation states this was the expected behavior.

  • Retries will no longer be performed when tasks are called directly (using __call__).

    Instead the exception passed to retry will be re-raised.

  • Eventlet no longer crashes if autoscale is enabled.

    growing and shrinking eventlet pools is still not supported.

  • py24 target removed from tox.ini.


release-date:2011-08-07 08:00 P.M BST
release-by:Ask Solem


  • The CELERY_AMQP_TASK_RESULT_EXPIRES setting did not work, resulting in an AMQP related error about not being able to serialize floats while trying to publish task states (Issue #446).


release-date:2011-08-05 12:00 P.M BST
tested:cPython: 2.5, 2.6, 2.7; PyPy: 1.5; Jython: 2.5.2
release-by:Ask Solem

Important Notes

  • Now requires Kombu 1.2.1

  • Results are now disabled by default.

    The AMQP backend was not a good default because often the users were not consuming the results, resulting in thousands of queues.

    While the queues can be configured to expire if left unused, it was not possible to enable this by default because this was only available in recent RabbitMQ versions (2.1.1+)

    With this change enabling a result backend will be a conscious choice, which will hopefully lead the user to read the documentation and be aware of any common pitfalls with the particular backend.

    The default backend is now a dummy backend (celery.backends.base.DisabledBackend). Saving state is simply an noop operation, and AsyncResult.wait(), .result, .state, etc. will raise a NotImplementedError telling the user to configure the result backend.

    For help choosing a backend please see Result Backends.

    If you depend on the previous default which was the AMQP backend, then you have to set this explicitly before upgrading:



    For django-celery users the default backend is still database, and results are not disabled by default.

  • The Debian init scripts have been deprecated in favor of the generic-init.d init scripts.

    In addition generic init scripts for celerybeat and celeryev has been added.


  • Automatic connection pool support.

    The pool is used by everything that requires a broker connection. For example calling tasks, sending broadcast commands, retrieving results with the AMQP result backend, and so on.

    The pool is disabled by default, but you can enable it by configuring the BROKER_POOL_LIMIT setting:


    A limit of 10 means a maximum of 10 simultaneous connections can co-exist. Only a single connection will ever be used in a single-thread environment, but in a concurrent environment (threads, greenlets, etc., but not processes) when the limit has been exceeded, any try to acquire a connection will block the thread and wait for a connection to be released. This is something to take into consideration when choosing a limit.

    A limit of None or 0 means no limit, and connections will be established and closed every time.

  • Introducing Chords (taskset callbacks).

    A chord is a task that only executes after all of the tasks in a taskset has finished executing. It’s a fancy term for “taskset callbacks” adopted from ).

    It works with all result backends, but the best implementation is currently provided by the Redis result backend.

    Here’s an example chord:

    >>> chord(add.subtask((i, i))
    ...         for i in xrange(100))(tsum.subtask()).get()

    Please read the Chords section in the user guide, if you want to know more.

  • Time limits can now be set for individual tasks.

    To set the soft and hard time limits for a task use the time_limit and soft_time_limit attributes:

    import time
    @task(time_limit=60, soft_time_limit=30)
    def sleeptask(seconds):

    If the attributes are not set, then the workers default time limits will be used.

    New in this version you can also change the time limits for a task at runtime using the time_limit() remote control command:

    >>> from celery.task import control
    >>> control.time_limit("tasks.sleeptask",
    ...                    soft=60, hard=120, reply=True)
    [{'': {'ok': 'time limits set successfully'}}]

    Only tasks that starts executing after the time limit change will be affected.


    Soft time limits will still not work on Windows or other platforms that do not have the SIGUSR1 signal.

  • Redis backend configuration directive names changed to include the

    CELERY_ prefix.

    Old setting name Replace with

    The old names are still supported but pending deprecation.

  • PyPy: The default pool implementation used is now multiprocessing if running on PyPy 1.5.

  • multi: now supports “pass through” options.

    Pass through options makes it easier to use celery without a configuration file, or just add last-minute options on the command line.

    Example use:

    $ celery multi start 4  -c 2  -- \
                                     broker.vhost=/               \
  • celerybeat: Now retries establishing the connection (Issue #419).

  • celeryctl: New list bindings command.

    Lists the current or all available bindings, depending on the broker transport used.

  • Heartbeat is now sent every 30 seconds (previously every 2 minutes).

  • ResultSet.join_native() and iter_native() is now supported by the Redis and Cache result backends.

    This is an optimized version of join() using the underlying backends ability to fetch multiple results at once.

  • Can now use SSL when sending error e-mails by enabling the EMAIL_USE_SSL setting.

  • events.default_dispatcher(): Context manager to easily obtain an event dispatcher instance using the connection pool.

  • Import errors in the configuration module will not be silenced anymore.

  • ResultSet.iterate: Now supports the timeout, propagate and interval arguments.

  • with_default_connection -> with default_connection

  • TaskPool.apply_async: Keyword arguments callbacks and errbacks has been renamed to callback and errback and take a single scalar value instead of a list.

  • No longer propagates errors occurring during process cleanup (Issue #365)

  • Added TaskSetResult.delete(), which will delete a previously saved taskset result.

  • Celerybeat now syncs every 3 minutes instead of only at shutdown (Issue #382).

  • Monitors now properly handles unknown events, so user-defined events are displayed.

  • Terminating a task on Windows now also terminates all of the tasks child processes (Issue #384).

  • worker: -I|--include option now always searches the current directory to import the specified modules.

  • Cassandra backend: Now expires results by using TTLs.

  • Functional test suite in funtests is now actually working properly, and passing tests.


  • celeryev was trying to create the pidfile twice.
  • celery.contrib.batches: Fixed problem where tasks failed silently (Issue #393).
  • Fixed an issue where logging objects would give “<Unrepresentable”, even though the objects were.
  • CELERY_TASK_ERROR_WHITE_LIST is now properly initialized in all loaders.
  • celeryd_detach now passes through command line configuration.
  • Remote control command add_consumer now does nothing if the queue is already being consumed from.

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