This document describes the current stable version of Celery (5.4). 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.



2018-23-03 16:00 PM IST


Omer Katz

  • Fixed a crash caused by tasks cycling between Celery 3 and Celery 4 workers.



2016-10-10 12:00 PM PDT


Ask Solem

  • Requirements

  • Fixed problem with chords in group introduced in 3.1.24 (Issue #3504).



2016-09-30 04:21 PM PDT


Ask Solem

  • Requirements

  • Now supports Task protocol 2 from the future 4.0 release.

    Workers running 3.1.24 are now able to process messages sent using the new task message protocol to be introduced in Celery 4.0.

    Users upgrading to Celery 4.0 when this is released are encouraged to upgrade to this version as an intermediate step, as this means workers not yet upgraded will be able to process messages from clients/workers running 4.0.

  • Task.send_events can now be set to disable sending of events for that task only.

    Example when defining the task:

    def add(x, y):
        return x + y
  • Utils: Fixed compatibility with recent versions (Issue #3262).

  • Canvas: Chord now forwards partial arguments to its subtasks.

    Fix contributed by Tayfun Sen.

  • App: Arguments to app such as backend, broker, etc are now pickled and sent to the child processes on Windows.

    Fix contributed by Jeremy Zafran.

  • Deployment: Generic init scripts now supports being symlinked in runlevel directories (Issue #3208).

  • Deployment: Updated CentOS scripts to work with CentOS 7.

    Contributed by Joe Sanford.

  • Events: The curses monitor no longer crashes when the result of a task is empty.

    Fix contributed by Dongweiming.

  • Worker: repr(worker) would crash when called early in the startup process (Issue #2514).

  • Tasks: GroupResult now defines __bool__ and __nonzero__.

    This is to fix an issue where a ResultSet or GroupResult with an empty result list are not properly tupled with the as_tuple() method when it is a parent result. This is due to the as_tuple() method performing a logical and operation on the ResultSet.

    Fix contributed by Colin McIntosh.

  • Worker: Fixed wrong values in autoscale related logging message.

    Fix contributed by @raducc.

  • Documentation improvements by

    • Alexandru Chirila

    • Michael Aquilina

    • Mikko Ekström

    • Mitchel Humpherys

    • Thomas A. Neil

    • Tiago Moreira Vieira

    • Yuriy Syrovetskiy

    • @dessant



2016-03-09 06:00 P.M PST


Ask Solem

  • Programs: Last release broke support for the --hostnmame argument to celery multi and celery worker --detach (Issue #3103).

  • Results: MongoDB result backend could crash the worker at startup if not configured using an URL.



2016-03-07 01:30 P.M PST


Ask Solem

  • Programs: The worker would crash immediately on startup on backend.as_uri() when using some result backends (Issue #3094).

  • Programs: celery multi/celery worker --detach would create an extraneous logfile including literal formats (e.g. %I) in the filename (Issue #3096).



2016-03-04 11:16 a.m. PST


Ask Solem

  • Requirements

    • Now depends on Kombu 3.0.34.

    • Now depends on billiard

  • Prefork pool: Fixes 100% CPU loop on Linux epoll (Issue #1845).

    Also potential fix for: Issue #2142, Issue #2606

  • Prefork pool: Fixes memory leak related to processes exiting (Issue #2927).

  • Worker: Fixes crash at start-up when trying to censor passwords in MongoDB and Cache result backend URLs (Issue #3079, Issue #3045, Issue #3049, Issue #3068, Issue #3073).

    Fix contributed by Maxime Verger.

  • Task: An exception is now raised if countdown/expires is less than -2147483648 (Issue #3078).

  • Programs: celery shell --ipython now compatible with newer versions.

  • Programs: The DuplicateNodeName warning emitted by inspect/control now includes a list of the node names returned.

    Contributed by Sebastian Kalinowski.

  • Utils: The .discard(item) method of LimitedSet didn’t actually remove the item (Issue #3087).

    Fix contributed by Dave Smith.

  • Worker: Node name formatting now emits less confusing error message for unmatched format keys (Issue #3016).

  • Results: RPC/AMQP backends: Fixed deserialization of JSON exceptions (Issue #2518).

    Fix contributed by Allard Hoeve.

  • Prefork pool: The process inqueue damaged error message now includes the original exception raised.

  • Documentation: Includes improvements by:

    • Jeff Widman.



2016-01-22 06:50 p.m. UTC


Ask Solem

  • Requirements

    • Now depends on Kombu 3.0.33.

    • Now depends on billiard

      Includes binary wheels for Microsoft Windows x86 and x86_64!

  • Task: Error emails now uses utf-8 character set by default (Issue #2737).

  • Task: Retry now forwards original message headers (Issue #3017).

  • Worker: Bootsteps can now hook into on_node_join/leave/lost.

    See Attributes for an example.

  • Events: Fixed handling of DST timezones (Issue #2983).

  • Results: Redis backend stopped respecting certain settings.

    Contributed by Jeremy Llewellyn.

  • Results: Database backend now properly supports JSON exceptions (Issue #2441).

  • Results: Redis new_join didn’t properly call task errbacks on chord error (Issue #2796).

  • Results: Restores Redis compatibility with Python < 2.10.0 (Issue #2903).

  • Results: Fixed rare issue with chord error handling (Issue #2409).

  • Tasks: Using queue-name values in CELERY_ROUTES now works again (Issue #2987).

  • General: Result backend password now sanitized in report output (Issue #2812, Issue #2004).

  • Configuration: Now gives helpful error message when the result backend configuration points to a module, and not a class (Issue #2945).

  • Results: Exceptions sent by JSON serialized workers are now properly handled by pickle configured workers.

  • Programs: celery control autoscale now works (Issue #2950).

  • Programs: celery beat --detached now runs after fork callbacks.

  • General: Fix for LRU cache implementation on Python 3.5 (Issue #2897).

    Contributed by Dennis Brakhane.

    Python 3.5’s OrderedDict doesn’t allow mutation while it is being iterated over. This breaks “update” if it is called with a dict larger than the maximum size.

    This commit changes the code to a version that doesn’t iterate over the dict, and should also be a little bit faster.

  • Init-scripts: The beat init-script now properly reports service as down when no pid file can be found.

    Eric Zarowny

  • Beat: Added cleaning of corrupted scheduler files for some storage backend errors (Issue #2985).

    Fix contributed by Aleksandr Kuznetsov.

  • Beat: Now syncs the schedule even if the schedule is empty.

    Fix contributed by Colin McIntosh.

  • Supervisord: Set higher process priority in the


    Contributed by George Tantiras.

  • Documentation: Includes improvements by:

    @Bryson Caleb Mingle Christopher Martin Dieter Adriaenssens Jason Veatch Jeremy Cline Juan Rossi Kevin Harvey Kevin McCarthy Kirill Pavlov Marco Buttu @Mayflower Mher Movsisyan Michael Floering @michael-k Nathaniel Varona Rudy Attias Ryan Luckie Steven Parker @squfrans Tadej Janež TakesxiSximada Tom S



2015-10-26 01:00 p.m. UTC


Ask Solem

  • Requirements

    • Now depends on Kombu 3.0.29.

    • Now depends on billiard

  • Results: Fixed MongoDB result backend URL parsing problem (Issue celery/kombu#375).

  • Worker: Task request now properly sets priority in delivery_info.

    Fix contributed by Gerald Manipon.

  • Beat: PyPy shelve may raise KeyError when setting keys (Issue #2862).

  • Programs: celery beat --deatched now working on PyPy.

    Fix contributed by Krzysztof Bujniewicz.

  • Results: Redis result backend now ensures all pipelines are cleaned up.

    Contributed by Justin Patrin.

  • Results: Redis result backend now allows for timeout to be set in the query portion of the result backend URL.

    For example CELERY_RESULT_BACKEND = 'redis://?timeout=10'

    Contributed by Justin Patrin.

  • Results: result.get now properly handles failures where the exception value is set to None (Issue #2560).

  • Prefork pool: Fixed attribute error proc.dead.

  • Worker: Fixed worker hanging when gossip/heartbeat disabled (Issue #1847).

    Fix contributed by Aaron Webber and Bryan Helmig.

  • Results: MongoDB result backend now supports pymongo 3.x (Issue #2744).

    Fix contributed by Sukrit Khera.

  • Results: RPC/AMQP backends didn’t deserialize exceptions properly (Issue #2691).

    Fix contributed by Sukrit Khera.

  • Programs: Fixed problem with celery amqp’s basic_publish (Issue #2013).

  • Worker: Embedded beat now properly sets app for thread/process (Issue #2594).

  • Documentation: Many improvements and typos fixed.

    Contributions by:

    Carlos Garcia-Dubus D. Yu @jerry Jocelyn Delalande Josh Kupershmidt Juan Rossi @kanemra Paul Pearce Pavel Savchenko Sean Wang Seungha Kim Zhaorong Ma



2015-04-22 05:30 p.m. UTC


Ask Solem

  • Requirements

    • Now depends on Kombu 3.0.25.

    • Now depends on billiard

  • Django: Now supports Django 1.8 (Issue #2536).

    Fix contributed by Bence Tamas and Mickaël Penhard.

  • Results: MongoDB result backend now compatible with pymongo 3.0.

    Fix contributed by Fatih Sucu.

  • Tasks: Fixed bug only happening when a task has multiple callbacks (Issue #2515).

    Fix contributed by NotSqrt.

  • Commands: Preload options now support --arg value syntax.

    Fix contributed by John Anderson.

  • Compat: A typo caused celery.log.setup_logging_subsystem to be undefined.

    Fix contributed by Gunnlaugur Thor Briem.

  • init-scripts: The beat generic init-script now uses /bin/sh instead of bash (Issue #2496).

    Fix contributed by Jelle Verstraaten.

  • Django: Fixed a TypeError sometimes occurring in logging when validating models.

    Fix contributed by Alexander.

  • Commands: Worker now supports new --executable argument that can be used with celery worker --detach.

    Contributed by Bert Vanderbauwhede.

  • Canvas: Fixed crash in chord unlock fallback task (Issue #2404).

  • Worker: Fixed rare crash occurring with --autoscale enabled (Issue #2411).

  • Django: Properly recycle worker Django database connections when the Django CONN_MAX_AGE setting is enabled (Issue #2453).

    Fix contributed by Luke Burden.



2014-11-19 03:30 p.m. UTC


Ask Solem

Don’t enable the CELERYD_FORCE_EXECV setting!

Please review your configuration and disable this option if you’re using the RabbitMQ or Redis transport.

Keeping this option enabled after 3.1 means the async based prefork pool will be disabled, which can easily cause instability.

  • Requirements

    • Now depends on Kombu 3.0.24.

      Includes the new Qpid transport coming in Celery 3.2, backported to support those who may still require Python 2.6 compatibility.

    • Now depends on billiard

    • celery[librabbitmq] now depends on librabbitmq 1.6.1.

  • Task: The timing of ETA/countdown tasks were off after the example LocalTimezone implementation in the Python documentation no longer works in Python 3.4. (Issue #2306).

  • Task: Raising Ignore no longer sends task-failed event (Issue #2365).

  • Redis result backend: Fixed unbound local errors.

    Fix contributed by Thomas French.

  • Task: Callbacks wasn’t called properly if link was a list of signatures (Issue #2350).

  • Canvas: chain and group now handles json serialized signatures (Issue #2076).

  • Results: .join_native() would accidentally treat the STARTED state as being ready (Issue #2326).

    This could lead to the chord callback being called with invalid arguments when using chords with the CELERY_TRACK_STARTED setting enabled.

  • Canvas: The chord_size attribute is now set for all canvas primitives, making sure more combinations will work with the new_join optimization for Redis (Issue #2339).

  • Task: Fixed problem with app not being properly propagated to trace_task in all cases.

    Fix contributed by @kristaps.

  • Worker: Expires from task message now associated with a timezone.

    Fix contributed by Albert Wang.

  • Cassandra result backend: Fixed problems when using detailed mode.

    When using the Cassandra backend in detailed mode, a regression caused errors when attempting to retrieve results.

    Fix contributed by Gino Ledesma.

  • Mongodb Result backend: Pickling the backend instance will now include the original URL (Issue #2347).

    Fix contributed by Sukrit Khera.

  • Task: Exception info wasn’t properly set for tasks raising Reject (Issue #2043).

  • Worker: Duplicates are now removed when loading the set of revoked tasks from the worker state database (Issue #2336).

  • celery.contrib.rdb: Fixed problems with rdb.set_trace calling stop from the wrong frame.

    Fix contributed by @llllllllll.

  • Canvas: chain and chord can now be immutable.

  • Canvas: chord.apply_async will now keep partial args set in self.args (Issue #2299).

  • Results: Small refactoring so that results are decoded the same way in all result backends.

  • Logging: The processName format was introduced in Python 2.6.2 so for compatibility this format is now excluded when using earlier versions (Issue #1644).



2014-10-03 06:00 p.m. UTC


Ask Solem

  • Worker: 3.1.15 broke -Ofair behavior (Issue #2286).

    This regression could result in all tasks executing in a single child process if -Ofair was enabled.

  • Canvas: celery.signature now properly forwards app argument in all cases.

  • Task: .retry() didn’t raise the exception correctly when called without a current exception.

    Fix contributed by Andrea Rabbaglietti.

  • Worker: The enable_events remote control command disabled worker-related events by mistake (Issue #2272).

    Fix contributed by Konstantinos Koukopoulos.

  • Django: Adds support for Django 1.7 class names in INSTALLED_APPS when using app.autodiscover_tasks() (Issue #2248).

  • Sphinx: celery.contrib.sphinx now uses getfullargspec on Python 3 (Issue #2302).

  • Redis/Cache Backends: Chords will now run at most once if one or more tasks in the chord are executed multiple times for some reason.



2014-09-14 11:00 p.m. UTC


Ask Solem

  • Django: Now makes sure django.setup() is called before importing any task modules (Django 1.7 compatibility, Issue #2227)

  • Results: result.get() was misbehaving by calling backend.get_task_meta in a finally call leading to AMQP result backend queues not being properly cleaned up (Issue #2245).



2014-09-08 03:00 p.m. UTC


Ask Solem

  • Requirements

  • Init-scripts: The generic worker init-scripts status command now gets an accurate pidfile list (Issue #1942).

  • Init-scripts: The generic beat script now implements the status


    Contributed by John Whitlock.

  • Commands: Multi now writes informational output to stdout instead of stderr.

  • Worker: Now ignores not implemented error for pool.restart (Issue #2153).

  • Task: Retry no longer raises retry exception when executed in eager mode (Issue #2164).

  • AMQP Result backend: Now ensured on_interval is called at least every second for blocking calls to properly propagate parent errors.

  • Django: Compatibility with Django 1.7 on Windows (Issue #2126).

  • Programs: --umask argument can now be specified in both octal (if starting with 0) or decimal.


Security Fixes

  • [Security: CELERYSA-0002] Insecure default umask.

    The built-in utility used to daemonize the Celery worker service sets an insecure umask by default (umask 0).

    This means that any files or directories created by the worker will end up having world-writable permissions.

    Special thanks to Red Hat for originally discovering and reporting the issue!

    This version will no longer set a default umask by default, so if unset the umask of the parent process will be used.


  • Requirements

    • Now depends on Kombu 3.0.21.

    • Now depends on billiard

  • App: backend argument now also sets the CELERY_RESULT_BACKEND setting.

  • Task: signature_from_request now propagates reply_to so that the RPC backend works with retried tasks (Issue #2113).

  • Task: retry will no longer attempt to re-queue the task if sending the retry message fails.

    Unrelated exceptions being raised could cause a message loop, so it was better to remove this behavior.

  • Beat: Accounts for standard 1ms drift by always waking up 0.010s earlier.

    This will adjust the latency so that the periodic tasks won’t move 1ms after every invocation.

  • Documentation fixes

    Contributed by Yuval Greenfield, Lucas Wiman, @nicholsonjf.

  • Worker: Removed an outdated assert statement that could lead to errors being masked (Issue #2086).



2014-06-09 10:12 p.m. UTC


Ask Solem

  • Requirements

    Now depends on Kombu 3.0.19.

  • App: Connections weren’t being closed after fork due to an error in the after fork handler (Issue #2055).

    This could manifest itself by causing framing errors when using RabbitMQ. (Unexpected frame).

  • Django: django.setup() was being called too late when using Django 1.7 (Issue #1802).

  • Django: Fixed problems with event timezones when using Django (Substantial drift).

    Celery didn’t take into account that Django modifies the time.timeone attributes and friends.

  • Canvas: now works when the link option is a scalar value (Issue #2019).

  • Prefork pool: Fixed race conditions for when file descriptors are removed from the event loop.

    Fix contributed by Roger Hu.

  • Prefork pool: Improved solution for dividing tasks between child processes.

    This change should improve performance when there are many child processes, and also decrease the chance that two subsequent tasks are written to the same child process.

  • Worker: Now ignores unknown event types, instead of crashing.

    Fix contributed by Illes Solt.

  • Programs: celery worker --detach no longer closes open file descriptors when C_FAKEFORK is used so that the workers output can be seen.

  • Programs: The default working directory for celery worker --detach is now the current working directory, not /.

  • Canvas: signature(s, app=app) didn’t upgrade serialized signatures to their original class (subtask_type) when the app keyword argument was used.

  • Control: The duplicate nodename warning emitted by control commands now shows the duplicate node name.

  • Tasks: Can now call ResultSet.get() on a result set without members.

    Fix contributed by Alexey Kotlyarov.

  • App: Fixed strange traceback mangling issue for app.connection_or_acquire.

  • Programs: The celery multi stopwait command is now documented in usage.

  • Other: Fixed cleanup problem with PromiseProxy when an error is raised while trying to evaluate the promise.

  • Other: The utility used to censor configuration values now handles non-string keys.

    Fix contributed by Luke Pomfrey.

  • Other: The inspect conf command didn’t handle non-string keys well.

    Fix contributed by Jay Farrimond.

  • Programs: Fixed argument handling problem in celery worker --detach.

    Fix contributed by Dmitry Malinovsky.

  • Programs: celery worker --detach didn’t forward working directory option (Issue #2003).

  • Programs: celery inspect registered no longer includes the list of built-in tasks.

  • Worker: The requires attribute for boot steps weren’t being handled correctly (Issue #2002).

  • Eventlet: The eventlet pool now supports the pool_grow and pool_shrink remote control commands.

    Contributed by Mher Movsisyan.

  • Eventlet: The eventlet pool now implements statistics for :program:celery inspect stats.

    Contributed by Mher Movsisyan.

  • Documentation: Clarified Task.rate_limit behavior.

    Contributed by Jonas Haag.

  • Documentation: AbortableTask examples now updated to use the new API (Issue #1993).

  • Documentation: The security documentation examples used an out of date import.

    Fix contributed by Ian Dees.

  • Init-scripts: The CentOS init-scripts didn’t quote CELERY_CHDIR.

    Fix contributed by @ffeast.



2014-04-16 11:00 p.m. UTC


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:

  • Tasks: The CELERY_DEFAULT_DELIVERY_MODE setting was being ignored (Issue #1953).

  • Worker: New celery worker --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).



2014-03-22 09:40 p.m. UTC


Ask Solem

  • Requirements:

  • 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’s 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 won’t 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 Caveats.

    This will be the default in Celery 3.2.

  • Results: The app.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 occurring when worker is started by

    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 isn’t 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).



2014-02-10 06:43 p.m. UTC


Ask Solem

  • Requirements:

  • 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 wasn’t 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 didn’t 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.



2014-01-17 10:45 p.m. UTC


Ask Solem

  • Worker: The event loop wasn’t 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 Control-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 start-up to verify that any configuration scripts are owned by root and that they aren’t world/group writable.

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


    Note that upgrading Celery won’t 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() didn’t raise the value provided in the exc argument when called outside of an error context (Issue #1755).

  • Commands: The celery multi command didn’t 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 start-up 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 macOS 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: examples contained an extraneous ‘-’ in a --logfile argument example.

    Fix contributed by Mohammad Almeer.



2013-12-17 06:00 p.m. UTC


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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 isn’t trusted with superuser privileges.

This isn’t 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’s 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’re doing you can avoid the warning (and the future exception being raised) by moving the operation in a white-list 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 won’t 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 didn’t 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 fallback 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’s set when a task-sent event is being received.

    Also, a clients logical clock isn’t 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 didn’t 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).



2013-12-02 06:00 p.m. UTC


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  • Now depends on billiard

  • Now depends on Kombu 3.0.7.

  • Fixed problem where Mingle caused the worker to hang at start-up (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 SysV style init symlinks.

    Fix contributed by Jonathan Jordan.

  • Events: Fixed problem when task name isn’t 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).



2013-11-21 06:20 p.m. UTC


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 isn’t prepared prematurely.

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

  • Worker: Now respects the --uid and --gid arguments even if --detach isn’t enabled.

  • Beat: Now respects the --uid and --gid arguments even if --detach isn’t enabled.

  • Python 3: Fixed unorderable error occurring 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 built-in fix-ups.

    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 didn’t 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 sub-command, these are now moved to the end instead.

  • Worker now properly responds to inspect stats commands even if received before start-up 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).



2013-11-15 11:40 p.m. UTC


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  • Now depends on Kombu 3.0.5.

  • Now depends on billiard

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

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

  • Worker: Fixed Unicode error crash at start-up 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 beat init-script.

    Fix contributed by Vsevolod.

  • Tests now passing on PyPy 2.1 and 2.2.



2013-11-13 00:55 a.m. UTC


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  • 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)



2013-11-12 08:00 p.m. UTC


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.



2013-11-11 06:30 p.m. UTC


Ask Solem

  • Now depends on billiard

  • Python 3: Fixed compatibility issues.

  • Windows: Accidentally showed warning that the billiard C extension wasn’t 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: Fix-up shouldn’t 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 wasn’t respected.



2013-11-09 11:00 p.m. UTC


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See What’s new in Celery 3.1 (Cipater).