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.. contents::
.. _version-2.5.0
:branch: master
* Adds Chord support for the memcached backend (Issue #533).
Contributed by Dan McGee.
* The `--uid` argument to daemons now uses ``initgroups()`` to set
groups to all the groups the user is a member of.
Fix contributed by Łukasz Oleś.
.. _version-2.4.4:
:release-date: 2011-11-25 16:00 P.M GMT
:by: Ask Solem
.. _v244-security-fixes:
Security Fixes
* [Security: `CELERYSA-0001`_] Daemons would set effective id's rather than
real id's when the :option:`--uid`/:option:`--gid` arguments to
:program:`celeryd-multi`, :program:`celeryd_detach`,
:program:`celerybeat` and :program:`celeryev` were used.
This means privileges weren't properly dropped, and that it would
be possible to regain supervisor privileges later.
.. _`CELERYSA-0001`:
.. _v244-fixes:
* Processes pool: Fixed rare deadlock at shutdown (Issue #523).
Fix contributed by Ionel Maries Christian.
* Webhook tasks issued the wrong HTTP POST headers (Issue #515).
The *Content-Type* header has been changed from
``application/json`` ⇒ ``application/x-www-form-urlencoded``,
and adds a proper *Content-Length* header.
Fix contributed by Mitar.
* Daemonization cookbook: Adds a configuration example using Django and
virtualenv together (Issue #505).
Contributed by Juan Ignacio Catalano.
* generic init scripts now automatically creates log and pid file
directories (Issue #545).
Contributed by Chris Streeter.
.. _version-2.4.3:
:release-date: 2011-11-22 18:00 P.M GMT
:by: Ask Solem
* Fixes module import typo in `celeryctl` (Issue #538).
Fix contributed by Chris Streeter.
.. _version-2.4.2:
:release-date: 2011-11-14 12:00 P.M GMT
:by: Ask Solem
* Program module no longer uses relative imports so that it is
possible to do ``python -m``.
.. _version-2.4.1:
:release-date: 2011-11-07 06:00 P.M GMT
:by: Ask Solem
* celeryctl inspect commands was missing output.
* processes pool: Decrease polling interval for less idle CPU usage.
* processes pool: MaybeEncodingError was not wrapped in ExceptionInfo
(Issue #524).
* celeryd: would silence errors occuring after task consumer started.
* logging: Fixed a bug where unicode in stdout redirected log messages
couldn't be written (Issue #522).
.. _version-2.4.0:
:release-date: 2011-11-04 04:00 P.M GMT
:by: Ask Solem
.. _v240-important:
Important Notes
* Now supports Python 3.
* Fixed deadlock in worker process handling (Issue #496).
A deadlock could occur after spawning new child processes because
the logging library's mutex was not properly reset after fork.
The symptoms of this bug affecting would be that the worker simply
stops processing tasks, as none of the workers child processes
are functioning. There was a greater chance of this bug occurring
with ``maxtasksperchild`` or a time-limit enabled.
This is a workaround for
Be aware that while this fixes the logging library lock,
there could still be other locks initialized in the parent
process, introduced by custom code.
Fix contributed by Harm Verhagen.
* AMQP Result backend: Now expires results by default.
The default expiration value is now taken from the
:setting:`CELERY_TASK_RESULT_EXPIRES` setting.
The old :setting:`CELERY_AMQP_TASK_RESULT_EXPIRES` setting has been
deprecated and will be removed in version 3.0.
Note that this means that the result backend requires RabbitMQ 1.1.0 or
higher, and that you have to disable expiration if you are running
with an older version. You can do so by disabling the
:setting:`CELERY_TASK_RESULT_EXPIRES` setting::
* Eventlet: Fixed problem with shutdown (Issue #457).
* Broker transports can be now be specified using URLs
The broker can now be specified as an URL instead.
This URL must have the format::
for example the default broker is written as::
The scheme is required, so that the host is identified
as an URL and not just a host name.
User, password, port and virtual_host are optional and
defaults to the particular transports default value.
.. note::
Note that the path component (virtual_host) always starts with a
forward-slash. This is necessary to distinguish between the virtual
host ``''`` (empty) and ``'/'``, which are both acceptable virtual
host names.
A virtual host of ``'/'`` becomes:
and a virtual host of ``''`` (empty) becomes::
So the leading slash in the path component is **always required**.
In addition the :setting:`BROKER_URL` setting has been added as an alias
to ``BROKER_HOST``. Any broker setting specified in both the URL and in
the configuration will be ignored, if a setting is not provided in the URL
then the value from the configuration will be used as default.
Also, programs now support the :option:`-b|--broker` option to specify
a broker URL on the command line::
$ celeryd -b redis://localhost
$ celeryctl -b amqp://guest:guest@localhost//e
The environment variable :envvar:`CELERY_BROKER_URL` can also be used to
easily override the default broker used.
* The deprecated :func:`celery.loaders.setup_loader` function has been removed.
* The :setting:`CELERY_TASK_ERROR_WHITELIST` setting has been replaced
by a more flexible approach (Issue #447).
The error mail sending logic is now available as ``Task.ErrorMail``,
with the implementation (for reference) in :mod:`celery.utils.mail`.
The error mail class can be sub-classed to gain complete control
of when error messages are sent, thus removing the need for a separate
white-list setting.
The :setting:`CELERY_TASK_ERROR_WHITELIST` setting has been deprecated,
and will be removed completely in version 3.0.
* Additional Deprecations
The following functions has been deprecated and is scheduled for removal in
version 3.0:
===================================== ===================================
**Old function** **Alternative**
===================================== ===================================
`celery.loaders.current_loader` `celery.current_app.loader`
`celery.loaders.load_settings` `celery.current_app.conf`
`celery.execute.apply` `Task.apply`
`celery.execute.apply_async` `Task.apply_async`
`celery.execute.delay_task` `celery.execute.send_task`
===================================== ===================================
The following settings has been deprecated and is scheduled for removal
in version 3.0:
===================================== ===================================
**Old setting** **Alternative**
===================================== ===================================
`CELERYD_LOG_LEVEL` ``celeryd --loglevel=``
`CELERYD_LOG_FILE` ``celeryd --logfile=``
`CELERYBEAT_LOG_LEVEL` ``celerybeat --loglevel=``
`CELERYBEAT_LOG_FILE` ``celerybeat --logfile=``
`CELERYMON_LOG_LEVEL` ``celerymon --loglevel=``
`CELERYMON_LOG_FILE` ``celerymon --logfile=``
===================================== ===================================
.. _v240-news:
* No longer depends on :mod:`pyparsing`.
* Now depends on Kombu 1.4.3.
* CELERY_IMPORTS can now be a scalar value (Issue #485).
It is too easy to forget to add the comma after the sole element of a
tuple, and this is something that often affects newcomers.
The docs should probably use a list in examples, as using a tuple
for this doesn't even make sense. Nonetheless, there are many
tutorials out there using a tuple, and this change should be a help
to new users.
Suggested by jsaxon-cars.
* Fixed a memory leak when using the thread pool (Issue #486).
Contributed by Kornelijus Survila.
* The statedb was not saved at exit.
This has now been fixed and it should again remember previously
revoked tasks when a ``--statedb`` is enabled.
* Adds :setting:`EMAIL_USE_TLS` to enable secure SMTP connections
(Issue #418).
Contributed by Stefan Kjartansson.
* Now handles missing fields in task messages as documented in the message
format documentation.
* Missing required field throws :exc:`InvalidTaskError`
* Missing args/kwargs is assumed empty.
Contributed by Chris Chamberlin.
* Fixed race condition in (celerymon/celeryev)
where task info would be removed while iterating over it (Issue #501).
* The Cache, Cassandra, MongoDB, Redis and Tyrant backends now respects
the :setting:`CELERY_RESULT_SERIALIZER` setting (Issue #435).
This means that only the database (django/sqlalchemy) backends
currently does not support using custom serializers.
Contributed by Steeve Morin
* Logging calls no longer manually formats messages, but delegates
that to the logging system, so tools like Sentry can easier
work with the messages (Issue #445).
Contributed by Chris Adams.
* ``celeryd_multi`` now supports a ``stop_verify`` command to wait for
processes to shutdown.
* Cache backend did not work if the cache key was unicode (Issue #504).
Fix contributed by Neil Chintomby.
* New setting :setting:`CELERY_RESULT_DB_SHORT_LIVED_SESSIONS` added,
which if enabled will disable the caching of SQLAlchemy sessions
(Issue #449).
Contributed by Leo Dirac.
* All result backends now implements ``__reduce__`` so that they can
be pickled (Issue #441).
Fix contributed by Remy Noel
* celeryd-multi did not work on Windows (Issue #472).
* New-style ``CELERY_REDIS_*`` settings now takes precedence over
the old ``REDIS_*`` configuration keys (Issue #508).
Fix contributed by Joshua Ginsberg
* Generic celerybeat init script no longer sets `bash -e` (Issue #510).
Fix contributed by Roger Hu.
* Documented that Chords do not work well with redis-server versions
before 2.2.
Contributed by Dan McGee.
* The :setting:`CELERYBEAT_MAX_LOOP_INTERVAL` setting was not respected.
* ``inspect.registered_tasks`` renamed to ``inspect.registered`` for naming
The previous name is still available as an alias.
Contributed by Mher Movsisyan
* Worker logged the string representation of args and kwargs
without safe guards (Issue #480).
* RHEL init script: Changed celeryd startup priority.
The default start / stop priorities for MySQL on RHEL are
# chkconfig: - 64 36
Therefore, if Celery is using a database as a broker / message store, it
should be started after the database is up and running, otherwise errors
will ensue. This commit changes the priority in the init script to
# chkconfig: - 85 15
which are the default recommended settings for 3-rd party applications
and assure that Celery will be started after the database service & shut
down before it terminates.
Contributed by Yury V. Zaytsev.
* KeyValueStoreBackend.get_many did not respect the ``timeout`` argument
(Issue #512).
* celerybeat/celeryev's --workdir option did not chdir before after
configuration was attempted (Issue #506).
* After deprecating 2.4 support we can now name modules correctly, since we
can take use of absolute imports.
Therefore the following internal modules have been renamed:
celery.concurrency.evlet -> celery.concurrency.eventlet
celery.concurrency.evg -> celery.concurrency.gevent
* AUTHORS file is now sorted alphabetically.
Also, as you may have noticed the contributors of new features/fixes are
now mentioned in the Changelog.
.. _version-2.3.4:
:release-date: 2011-11-25 16:00 P.M GMT
:by: Ask Solem
.. _v234-security-fixes:
Security Fixes
* [Security: `CELERYSA-0001`_] Daemons would set effective id's rather than
real id's when the :option:`--uid`/:option:`--gid` arguments to
:program:`celeryd-multi`, :program:`celeryd_detach`,
:program:`celerybeat` and :program:`celeryev` were used.
This means privileges weren't properly dropped, and that it would
be possible to regain supervisor privileges later.
.. _`CELERYSA-0001`:
* 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.
.. _version-2.3.3:
:release-date: 2011-16-09 05:00 P.M BST
:by: Mher Movsisyan
* Monkey patching :attr:`sys.stdout` could result in the worker
crashing if the replacing object did not define :meth:`isatty`
(Issue #477).
* ``CELERYD`` option in :file:`/etc/default/celeryd` should not
be used with generic init scripts.
.. _version-2.3.2:
:release-date: 2011-10-07 05:00 P.M BST
.. _v232-news:
* Improved Contributing guide.
If you'd like to contribute to Celery you should read this
We are looking for contributors at all skill levels, so don't
* 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.
(see :class:``).
.. _v232-fixes:
* `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 :file:`tox.ini`.
.. _version-2.3.1:
:release-date: 2011-08-07 08:00 P.M BST
* The :setting:`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).
.. _version-2.3.0:
: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
.. _v230-important:
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
(:class:`celery.backends.base.DisabledBackend`). Saving state is simply an
noop operation, and AsyncResult.wait(), .result, .state, etc. will raise
a :exc:`NotImplementedError` telling the user to configure the result backend.
For help choosing a backend please see :ref:`task-result-backends`.
If you depend on the previous default which was the AMQP backend, then
you have to set this explicitly before upgrading::
.. note::
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
.. _v230-news:
* Automatic connection pool support.
The pool is used by everything that requires a broker connection. For
example applying 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
:setting:`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 :const:`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
`Cω <>`_).
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 :ref:`Chords section in the user guide <chords>`, 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:
.. code-block:: python
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 :func:`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.
.. note::
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.
* celeryd-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
Example use:
$ celeryd-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
:setting:`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).
* celeryd: ``-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.
.. _v230-fixes:
* 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.
.. _version-2.2.8:
:release-date: 2011-11-25 16:00 P.M GMT
:by: Ask Solem
.. _v228-security-fixes:
Security Fixes
* [Security: `CELERYSA-0001`_] Daemons would set effective id's rather than
real id's when the :option:`--uid`/:option:`--gid` arguments to
:program:`celeryd-multi`, :program:`celeryd_detach`,
:program:`celerybeat` and :program:`celeryev` were used.
This means privileges weren't properly dropped, and that it would
be possible to regain supervisor privileges later.
.. _`CELERYSA-0001`:
.. _version-2.2.7:
:release-date: 2011-06-13 16:00 P.M BST
* New signals: :signal:`after_setup_logger` and
These signals can be used to augment logging configuration
after Celery has set up logging.
* Redis result backend now works with Redis 2.4.4.
* celeryd_multi: The :option:`--gid` option now works correctly.
* celeryd: Retry wrongfully used the repr of the traceback instead
of the string representation.
* App.config_from_object: Now loads module, not attribute of module.
* Fixed issue where logging of objects would give "<Unrepresentable: ...>"
.. _version-2.2.6:
:release-date: 2011-04-15 16:00 P.M CEST
.. _v226-important:
Important Notes
* Now depends on Kombu 1.1.2.
* Dependency lists now explicitly specifies that we don't want python-dateutil
2.x, as this version only supports py3k.
If you have installed dateutil 2.0 by accident you should downgrade
to the 1.5.0 version::
pip install -U python-dateutil==1.5.0
or by easy_install::
easy_install -U python-dateutil==1.5.0
.. _v226-fixes:
* The new ``WatchedFileHandler`` broke Python 2.5 support (Issue #367).
* Task: Don't use ``app.main`` if the task name is set explicitly.
* Sending emails did not work on Python 2.5, due to a bug in
the version detection code (Issue #378).
* Beat: Adds method ``ScheduleEntry._default_now``
This method can be overridden to change the default value
of ``last_run_at``.
* An error occurring in process cleanup could mask task errors.
We no longer propagate errors happening at process cleanup,
but log them instead. This way they will not interfere with publishing
the task result (Issue #365).
* Defining tasks did not work properly when using the Django
``shell_plus`` utility (Issue #366).
* ``AsyncResult.get`` did not accept the ``interval`` and ``propagate``
* celeryd: Fixed a bug where celeryd would not shutdown if a
:exc:`socket.error` was raised.
.. _version-2.2.5:
:release-date: 2011-03-28 06:00 P.M CEST
.. _v225-important:
Important Notes
* Now depends on Kombu 1.0.7
.. _v225-news:
* Our documentation is now hosted by Read The Docs
(, and all links have been changed to point to
the new URL.
* Logging: Now supports log rotation using external tools like `logrotate.d`_
(Issue #321)
This is accomplished by using the ``WatchedFileHandler``, which re-opens
the file if it is renamed or deleted.
.. _`logrotate.d`:
* :ref:`tut-otherqueues` now documents how to configure Redis/Database result
* gevent: Now supports ETA tasks.
But gevent still needs ``CELERY_DISABLE_RATE_LIMITS=True`` to work.
* TaskSet User Guide: now contains TaskSet callback recipes.
* Eventlet: New signals:
* ``eventlet_pool_started``
* ``eventlet_pool_preshutdown``
* ``eventlet_pool_postshutdown``
* ``eventlet_pool_apply``
See :mod:`celery.signals` for more information.
* New :setting:`BROKER_TRANSPORT_OPTIONS` setting can be used to pass
additional arguments to a particular broker transport.
* celeryd: ``worker_pid`` is now part of the request info as returned by
broadcast commands.
* TaskSet.apply/Taskset.apply_async now accepts an optional ``taskset_id``
* The taskset_id (if any) is now available in the Task request context.
* SQLAlchemy result backend: taskset_id and taskset_id columns now have a
unique constraint. (Tables need to recreated for this to take affect).
* Task Userguide: Added section about choosing a result backend.
* Removed unused attribute ``AsyncResult.uuid``.
.. _v225-fixes:
* multiprocessing.Pool: Fixes race condition when marking job with
``WorkerLostError`` (Issue #268).
The process may have published a result before it was terminated,
but we have no reliable way to detect that this is the case.
So we have to wait for 10 seconds before marking the result with
WorkerLostError. This gives the result handler a chance to retrieve the
* multiprocessing.Pool: Shutdown could hang if rate limits disabled.
There was a race condition when the MainThread was waiting for the pool
semaphore to be released. The ResultHandler now terminates after 5
seconds if there are unacked jobs, but no worker processes left to start
them (it needs to timeout because there could still be an ack+result
that we haven't consumed from the result queue. It
is unlikely we will receive any after 5 seconds with no worker processes).
* celerybeat: Now creates pidfile even if the ``--detach`` option is not set.
* eventlet/gevent: The broadcast command consumer is now running in a separate
This ensures broadcast commands will take priority even if there are many
active tasks.
* Internal module ``celery.worker.controllers`` renamed to
* celeryd: Threads now terminates the program by calling ``os._exit``, as it
is the only way to ensure exit in the case of syntax errors, or other
unrecoverable errors.
* Fixed typo in ``maybe_timedelta`` (Issue #352).
* celeryd: Broadcast commands now logs with loglevel debug instead of warning.
* AMQP Result Backend: Now resets cached channel if the connection is lost.
* Polling results with the AMQP result backend was not working properly.
* Rate limits: No longer sleeps if there are no tasks, but rather waits for
the task received condition (Performance improvement).
* ConfigurationView: ``iter(dict)`` should return keys, not items (Issue #362).
* celerybeat: PersistentScheduler now automatically removes a corrupted
schedule file (Issue #346).
* Programs that doesn't support positional command line arguments now provides
a user friendly error message.
* Programs no longer tries to load the configuration file when showing
``--version`` (Issue #347).
* Autoscaler: The "all processes busy" log message is now severity debug
instead of error.
* celeryd: If the message body can't be decoded, it is now passed through
``safe_str`` when logging.
This to ensure we don't get additional decoding errors when trying to log
the failure.
* ``app.config_from_object``/``app.config_from_envvar`` now works for all
* Now emits a user-friendly error message if the result backend name is
unknown (Issue #349).
* :mod:`celery.contrib.batches`: Now sets loglevel and logfile in the task
request so ``task.get_logger`` works with batch tasks (Issue #357).
* celeryd: An exception was raised if using the amqp transport and the prefetch
count value exceeded 65535 (Issue #359).
The prefetch count is incremented for every received task with an
ETA/countdown defined. The prefetch count is a short, so can only support
a maximum value of 65535. If the value exceeds the maximum value we now
disable the prefetch count, it is re-enabled as soon as the value is below
the limit again.
* cursesmon: Fixed unbound local error (Issue #303).
* eventlet/gevent is now imported on demand so autodoc can import the modules
without having eventlet/gevent installed.
* celeryd: Ack callback now properly handles ``AttributeError``.
* ``Task.after_return`` is now always called *after* the result has been
* Cassandra Result Backend: Should now work with the latest ``pycassa``
* multiprocessing.Pool: No longer cares if the putlock semaphore is released
too many times. (this can happen if one or more worker processes are
* SQLAlchemy Result Backend: Now returns accidentally removed ``date_done`` again
(Issue #325).
* Task.request contex is now always initialized to ensure calling the task
function directly works even if it actively uses the request context.
* Exception occuring when iterating over the result from ``TaskSet.apply``
* eventlet: Now properly schedules tasks with an ETA in the past.
.. _version-2.2.4:
:release-date: 2011-02-19 12:00 AM CET
.. _v224-fixes:
* celeryd: 2.2.3 broke error logging, resulting in tracebacks not being logged.
* AMQP result backend: Polling task states did not work properly if there were
more than one result message in the queue.
* ``TaskSet.apply_async()`` and ``TaskSet.apply()`` now supports an optional
``taskset_id`` keyword argument (Issue #331).
* The current taskset id (if any) is now available in the task context as
``request.taskset`` (Issue #329).
* SQLAlchemy result backend: `date_done` was no longer part of the results as it had
been accidentally removed. It is now available again (Issue #325).
* SQLAlchemy result backend: Added unique constraint on `Task.task_id` and
`TaskSet.taskset_id`. Tables needs to be recreated for this to take effect.
* Fixed exception raised when iterating on the result of ``TaskSet.apply()``.
* Tasks Userguide: Added section on choosing a result backend.
.. _version-2.2.3:
:release-date: 2011-02-12 04:00 P.M CET
.. _v223-fixes:
* Now depends on Kombu 1.0.3
* Task.retry now supports a ``max_retries`` argument, used to change the
default value.
* `multiprocessing.cpu_count` may raise :exc:`NotImplementedError` on
platforms where this is not supported (Issue #320).
* Coloring of log messages broke if the logged object was not a string.
* Fixed several typos in the init script documentation.
* A regression caused `` and `Task.routing_key` to no longer
have any effect. This is now fixed.
* Routing Userguide: Fixes typo, routers in :setting:`CELERY_ROUTES` must be
instances, not classes.
* :program:`celeryev` did not create pidfile even though the
:option:`--pidfile` argument was set.
* Task logger format was no longer used. (Issue #317).
The id and name of the task is now part of the log message again.
* A safe version of ``repr()`` is now used in strategic places to ensure
objects with a broken ``__repr__`` does not crash the worker, or otherwise
make errors hard to understand (Issue #298).
* Remote control command ``active_queues``: did not account for queues added
at runtime.
In addition the dictionary replied by this command now has a different
structure: the exchange key is now a dictionary containing the
exchange declaration in full.
* The :option:`-Q` option to :program:`celeryd` removed unused queue
declarations, so routing of tasks could fail.
Queues are no longer removed, but rather `app.amqp.queues.consume_from()`
is used as the list of queues to consume from.
This ensures all queues are available for routing purposes.
* celeryctl: Now supports the `inspect active_queues` command.
.. _version-2.2.2:
:release-date: 2011-02-03 04:00 P.M CET
.. _v222-fixes:
* Celerybeat could not read the schedule properly, so entries in
:setting:`CELERYBEAT_SCHEDULE` would not be scheduled.
* Task error log message now includes `exc_info` again.
* The `eta` argument can now be used with `task.retry`.
Previously it was overwritten by the countdown argument.
* celeryd-multi/celeryd_detach: Now logs errors occuring when executing
the `celeryd` command.
* daemonizing cookbook: Fixed typo ``--time-limit 300`` ->
* Colors in logging broke non-string objects in log messages.
* ``setup_task_logger`` no longer makes assumptions about magic task kwargs.
.. _version-2.2.1:
:release-date: 2011-02-02 04:00 P.M CET
.. _v221-fixes:
* Eventlet pool was leaking memory (Issue #308).
* Deprecated function ``celery.execute.delay_task`` was accidentally removed,
now available again.
* ``BasePool.on_terminate`` stub did not exist
* celeryd detach: Adds readable error messages if user/group name does not
* Smarter handling of unicode decod errors when logging errors.
.. _version-2.2.0:
:release-date: 2011-02-01 10:00 AM CET
.. _v220-important:
Important Notes
* Carrot has been replaced with `Kombu`_
Kombu is the next generation messaging framework for Python,
fixing several flaws present in Carrot that was hard to fix
without breaking backwards compatibility.
Also it adds:
* First-class support for virtual transports; Redis, Django ORM,
SQLAlchemy, Beanstalk, MongoDB, CouchDB and in-memory.
* Consistent error handling with introspection,
* The ability to ensure that an operation is performed by gracefully
handling connection and channel errors,
* Message compression (zlib, bzip2, or custom compression schemes).
This means that `ghettoq` is no longer needed as the
functionality it provided is already available in Celery by default.
The virtual transports are also more feature complete with support
for exchanges (direct and topic). The Redis transport even supports
fanout exchanges so it is able to perform worker remote control
.. _`Kombu`:
* Magic keyword arguments pending deprecation.
The magic keyword arguments were responsibile for many problems
and quirks: notably issues with tasks and decorators, and name
collisions in keyword arguments for the unaware.
It wasn't easy to find a way to deprecate the magic keyword arguments,
but we think this is a solution that makes sense and it will not
have any adverse effects for existing code.
The path to a magic keyword argument free world is:
* the `celery.decorators` module is deprecated and the decorators
can now be found in `celery.task`.
* The decorators in `celery.task` disables keyword arguments by
* All examples in the documentation have been changed to use
This means that the following will have magic keyword arguments
enabled (old style):
.. code-block:: python
from celery.decorators import task
def add(x, y, **kwargs):
print("In task %s" % kwargs["task_id"])
return x + y
And this will not use magic keyword arguments (new style):
.. code-block:: python
from celery.task import task
def add(x, y):
print("In task %s" %
return x + y
In addition, tasks can choose not to accept magic keyword arguments by
setting the `task.accept_magic_kwargs` attribute.
.. admonition:: Deprecation
Using the decorators in :mod:`celery.decorators` emits a
:class:`PendingDeprecationWarning` with a helpful message urging
you to change your code, in version 2.4 this will be replaced with
a :class:`DeprecationWarning`, and in version 3.0 the
:mod:`celery.decorators` module will be removed and no longer exist.
Similarly, the `task.accept_magic_kwargs` attribute will no
longer have any effect starting from version 3.0.
* The magic keyword arguments are now available as `task.request`
This is called *the context*. Using thread-local storage the
context contains state that is related to the current request.
It is mutable and you can add custom attributes that will only be seen
by the current task request.
The following context attributes are always available:
===================================== ===================================
**Magic Keyword Argument** **Replace with**
===================================== ===================================
`kwargs["task_id"]` ``
`kwargs["delivery_info"]` `self.request.delivery_info`
`kwargs["task_retries"]` `self.request.retries`
`kwargs["logfile"]` `self.request.logfile`
`kwargs["loglevel"]` `self.request.loglevel`
`kwargs["task_is_eager` `self.request.is_eager`
**NEW** `self.request.args`
**NEW** `self.request.kwargs`
===================================== ===================================
In addition, the following methods now automatically uses the current
context, so you don't have to pass `kwargs` manually anymore:
* `task.retry`
* `task.get_logger`
* `task.update_state`
* `Eventlet`_ support.
This is great news for I/O-bound tasks!
To change pool implementations you use the :option:`-P|--pool` argument
to :program:`celeryd`, or globally using the
:setting:`CELERYD_POOL` setting. This can be the full name of a class,
or one of the following aliases: `processes`, `eventlet`, `gevent`.
For more information please see the :ref:`concurrency-eventlet` section
in the User Guide.
.. admonition:: Why not gevent?
For our first alternative concurrency implementation we have focused
on `Eventlet`_, but there is also an experimental `gevent`_ pool
available. This is missing some features, notably the ability to
schedule ETA tasks.
Hopefully the `gevent`_ support will be feature complete by
version 2.3, but this depends on user demand (and contributions).
.. _`Eventlet`:
.. _`gevent`:
* Python 2.4 support deprecated!
We're happy^H^H^H^H^Hsad to announce that this is the last version
to support Python 2.4.
You are urged to make some noise if you're currently stuck with
Python 2.4. Complain to your package maintainers, sysadmins and bosses:
tell them it's time to move on!
Apart from wanting to take advantage of with-statements, coroutines,
conditional expressions and enhanced try blocks, the code base
now contains so many 2.4 related hacks and workarounds it's no longer
just a compromise, but a sacrifice.
If it really isn't your choice, and you don't have the option to upgrade
to a newer version of Python, you can just continue to use Celery 2.2.
Important fixes can be backported for as long as there is interest.
* `celeryd`: Now supports Autoscaling of child worker processes.
The :option:`--autoscale` option can be used to configure the minimum
and maximum number of child worker processes::
Enable autoscaling by providing
max_concurrency,min_concurrency. Example:
--autoscale=10,3 (always keep 3 processes, but grow to
10 if necessary).
* Remote Debugging of Tasks
``celery.contrib.rdb`` is an extended version of :mod:`pdb` that
enables remote debugging of processes that does not have terminal
Example usage:
.. code-block:: python
from celery.contrib import rdb
from celery.task import task
def add(x, y):
result = x + y
rdb.set_trace() # <- set breakpoint
return result
:func:`~celery.contrib.rdb.set_trace` sets a breakpoint at the current
location and creates a socket you can telnet into to remotely debug
your task.
The debugger may be started by multiple processes at the same time,
so rather than using a fixed port the debugger will search for an
available port, starting from the base port (6900 by default).
The base port can be changed using the environment variable
By default the debugger will only be available from the local host,
to enable access from the outside you have to set the environment
variable :envvar:`CELERY_RDB_HOST`.
When `celeryd` encounters your breakpoint it will log the following
[INFO/MainProcess] Got task from broker:
[WARNING/PoolWorker-1] Remote Debugger:6900:
Please telnet 6900. Type `exit` in session to continue.
[2011-01-18 14:25:44,119: WARNING/PoolWorker-1] Remote Debugger:6900:
Waiting for client...
If you telnet the port specified you will be presented
with a ``pdb`` shell::
$ telnet localhost 6900
Connected to localhost.
Escape character is '^]'.
> /opt/devel/demoapp/
-> return result
Enter ``help`` to get a list of available commands,
It may be a good idea to read the `Python Debugger Manual`_ if
you have never used `pdb` before.
.. _`Python Debugger Manual`:
* Events are now transient and is using a topic exchange (instead of direct).
`CELERYD_EVENT_EXCHANGE_TYPE` settings are no longer in use.
This means events will not be stored until there is a consumer, and the
events will be gone as soon as the consumer stops. Also it means there
can be multiple monitors running at the same time.
The routing key of an event is the type of event (e.g. `worker.started`,
`worker.heartbeat`, `task.succeeded`, etc. This means a consumer can
filter on specific types, to only be alerted of the events it cares about.
Each consumer will create a unique queue, meaning it is in effect a
broadcast exchange.
This opens up a lot of possibilities, for example the workers could listen
for worker events to know what workers are in the neighborhood, and even
restart workers when they go down (or use this information to optimize
.. note::
The event exchange has been renamed from "celeryevent" to "celeryev"
so it does not collide with older versions.
If you would like to remove the old exchange you can do so
by executing the following command::
$ camqadm exchange.delete celeryevent
* `celeryd` now starts without configuration, and configuration can be
specified directly on the command line.
Configuration options must appear after the last argument, separated
by two dashes::
$ celeryd -l info -I tasks -- broker.vhost=/app
* Configuration is now an alias to the original configuration, so changes
to the original will reflect Celery at runtime.
* `celery.conf` has been deprecated, and modifying `celery.conf.ALWAYS_EAGER`
will no longer have any effect.
The default configuration is now available in the
:mod:`` module. The available configuration options
and their types can now be introspected.
* Remote control commands are now provided by `kombu.pidbox`, the generic
process mailbox.
* Internal module `celery.worker.listener` has been renamed to
`celery.worker.consumer`, and `.CarrotListener` is now `.Consumer`.
* Previously deprecated modules `celery.models` and
`` have now been removed as per the deprecation
* [Security: Low severity] Removed `celery.task.RemoteExecuteTask` and
accompanying functions: `dmap`, `dmap_async`, and `execute_remote`.
Executing arbitrary code using pickle is a potential security issue if
someone gains unrestricted access to the message broker.
If you really need this functionality, then you would have to add
this to your own project.
* [Security: Low severity] The `stats` command no longer transmits the
broker password.
One would have needed an authenticated broker connection to receive
this password in the first place, but sniffing the password at the
wire level would have been possible if using unencrypted communication.
.. _v220-news:
* The internal module `celery.task.builtins` has been removed.
* The module `celery.task.schedules` is deprecated, and
`celery.schedules` should be used instead.
For example if you have::
from celery.task.schedules import crontab
You should replace that with::
from celery.schedules import crontab
The module needs to be renamed because it must be possible
to import schedules without importing the `celery.task` module.
* The following functions have been deprecated and is scheduled for
removal in version 2.3:
* `celery.execute.apply_async`
Use `task.apply_async()` instead.
* `celery.execute.apply`
Use `task.apply()` instead.
* `celery.execute.delay_task`
Use `registry.tasks[name].delay()` instead.
* Importing `TaskSet` from `celery.task.base` is now deprecated.
You should use::
>>> from celery.task import TaskSet
* New remote control commands:
* `active_queues`
Returns the queue declarations a worker is currently consuming from.
* Added the ability to retry publishing the task message in
the event of connection loss or failure.
This is disabled by default but can be enabled using the
:setting:`CELERY_TASK_PUBLISH_RETRY` setting, and tweaked by
the :setting:`CELERY_TASK_PUBLISH_RETRY_POLICY` setting.
In addition `retry`, and `retry_policy` keyword arguments have
been added to `Task.apply_async`.
.. note::
Using the `retry` argument to `apply_async` requires you to
handle the publisher/connection manually.
* Periodic Task classes (`@periodic_task`/`PeriodicTask`) will *not* be
deprecated as previously indicated in the source code.
But you are encouraged to use the more flexible
:setting:`CELERYBEAT_SCHEDULE` setting.
* Built-in daemonization support of celeryd using `celeryd-multi`
is no longer experimental and is considered production quality.
See :ref:`daemon-generic` if you want to use the new generic init
* Added support for message compression using the
:setting:`CELERY_MESSAGE_COMPRESSION` setting, or the `compression` argument
to `apply_async`. This can also be set using routers.
* `celeryd`: Now logs stacktrace of all threads when receiving the
`SIGUSR1` signal. (Does not work on cPython 2.4, Windows or Jython).
Inspired by
* Can now remotely terminate/kill the worker process currently processing
a task.
The `revoke` remote control command now supports a `terminate` argument
Default signal is `TERM`, but can be specified using the `signal`
argument. Signal can be the uppercase name of any signal defined
in the :mod:`signal` module in the Python Standard Library.
Terminating a task also revokes it.
>>> from celery.task.control import revoke
>>> revoke(task_id, terminate=True)
>>> revoke(task_id, terminate=True, signal="KILL")
>>> revoke(task_id, terminate=True, signal="SIGKILL")
* `TaskSetResult.join_native`: Backend-optimized version of `join()`.
If available, this version uses the backends ability to retrieve
multiple results at once, unlike `join()` which fetches the results
one by one.
So far only supported by the AMQP result backend. Support for memcached
and Redis may be added later.
* Improved implementations of `TaskSetResult.join` and `AsyncResult.wait`.
An `interval` keyword argument have been added to both so the
polling interval can be specified (default interval is 0.5 seconds).
A `propagate` keyword argument have been added to `result.wait()`,
errors will be returned instead of raised if this is set to False.
.. warning::
You should decrease the polling interval when using the database
result backend, as frequent polling can result in high database load.
* The PID of the child worker process accepting a task is now sent as a field
with the `task-started` event.
* The following fields have been added to all events in the worker class:
* `sw_ident`: Name of worker software (e.g. celeryd).
* `sw_ver`: Software version (e.g. 2.2.0).
* `sw_sys`: Operating System (e.g. Linux, Windows, Darwin).
* For better accuracy the start time reported by the multiprocessing worker
process is used when calculating task duration.
Previously the time reported by the accept callback was used.
* `celerybeat`: New built-in daemonization support using the `--detach`
* `celeryev`: New built-in daemonization support using the `--detach`
* `TaskSet.apply_async`: Now supports custom publishers by using the
`publisher` argument.
* Added :setting:`CELERY_SEND_TASK_SENT_EVENT` setting.
If enabled an event will be sent with every task, so monitors can
track tasks before the workers receive them.
* `celerybeat`: Now reuses the broker connection when applying
scheduled tasks.
* The configuration module and loader to use can now be specified on
the command line.
For example::
$ celeryd --loader=myloader.Loader
* Added signals: `beat_init` and `beat_embedded_init`
* :signal:`celery.signals.beat_init`
Dispatched when :program:`celerybeat` starts (either standalone or
embedded). Sender is the :class:`celery.beat.Service` instance.
* :signal:`celery.signals.beat_embedded_init`
Dispatched in addition to the :signal:`beat_init` signal when
:program:`celerybeat` is started as an embedded process. Sender
is the :class:`celery.beat.Service` instance.
* Redis result backend: Removed deprecated settings `REDIS_TIMEOUT` and
* CentOS init script for :program:`celeryd` now available in `contrib/centos`.
* Now depends on `pyparsing` version 1.5.0 or higher.
There have been reported issues using Celery with pyparsing 1.4.x,
so please upgrade to the latest version.
* Lots of new unit tests written, now with a total coverage of 95%.
.. _v220-fixes:
* `celeryev` Curses Monitor: Improved resize handling and UI layout
(Issue #274 + Issue #276)
* AMQP Backend: Exceptions occurring while sending task results are now
propagated instead of silenced.
`celeryd` will then show the full traceback of these errors in the log.
* AMQP Backend: No longer deletes the result queue after successful
poll, as this should be handled by the
:setting:`CELERY_AMQP_TASK_RESULT_EXPIRES` setting instead.
* AMQP Backend: Now ensures queues are declared before polling results.
* Windows: celeryd: Show error if running with `-B` option.
Running celerybeat embedded is known not to work on Windows, so
users are encouraged to run celerybeat as a separate service instead.
* Windows: Utilities no longer output ANSI color codes on Windows
* camqadm: Now properly handles Ctrl+C by simply exiting instead of showing
confusing traceback.
* Windows: All tests are now passing on Windows.
* Remove bin/ directory, and `scripts` section from
This means we now rely completely on setuptools entrypoints.
.. _v220-experimental:
* Jython: celeryd now runs on Jython using the threaded pool.
All tests pass, but there may still be bugs lurking around the corners.
* PyPy: celeryd now runs on PyPy.
It runs without any pool, so to get parallel execution you must start
multiple instances (e.g. using :program:`celeryd-multi`).
Sadly an initial benchmark seems to show a 30% performance decrease on
pypy-1.4.1 + JIT. We would like to find out why this is, so stay tuned.
* :class:`PublisherPool`: Experimental pool of task publishers and
connections to be used with the `retry` argument to `apply_async`.
The example code below will re-use connections and channels, and
retry sending of the task message if the connection is lost.
.. code-block:: python
from celery import current_app
# Global pool
pool = current_app().amqp.PublisherPool(limit=10)
def my_view(request):
with pool.acquire() as publisher:
add.apply_async((2, 2), publisher=publisher, retry=True)
.. _version-2.1.4:
:release-date: 2010-12-03 12:00 P.M CEST
.. _v214-fixes:
* Execution options to `apply_async` now takes precedence over options
returned by active routers. This was a regression introduced recently
(Issue #244).
* `celeryev` curses monitor: Long arguments are now truncated so curses
doesn't crash with out of bounds errors. (Issue #235).
* `celeryd`: Channel errors occurring while handling control commands no
longer crash the worker but are instead logged with severity error.
* SQLAlchemy database backend: Fixed a race condition occurring when
the client wrote the pending state. Just like the Django database backend,
it does no longer save the pending state (Issue #261 + Issue #262).
* Error email body now uses `repr(exception)` instead of `str(exception)`,
as the latter could result in Unicode decode errors (Issue #245).
* Error email timeout value is now configurable by using the
:setting:`EMAIL_TIMEOUT` setting.
* `celeryev`: Now works on Windows (but the curses monitor won't work without
having curses).
* Unit test output no longer emits non-standard characters.
* `celeryd`: The broadcast consumer is now closed if the connection is reset.
* `celeryd`: Now properly handles errors occurring while trying to acknowledge
the message.
* `TaskRequest.on_failure` now encodes traceback using the current filesystem
encoding. (Issue #286).
* `EagerResult` can now be pickled (Issue #288).
.. _v214-documentation:
* Adding :ref:`contributing`.
* Added :ref:`guide-optimizing`.
* Added :ref:`faq-security` section to the FAQ.
.. _version-2.1.3:
:release-date: 2010-11-09 05:00 P.M CEST
.. _v213-fixes:
* Fixed deadlocks in `timer2` which could lead to `djcelerymon`/`celeryev -c`
* `EventReceiver`: now sends heartbeat request to find workers.
This means :program:`celeryev` and friends finds workers immediately
at startup.
* celeryev cursesmon: Set screen_delay to 10ms, so the screen refreshes more
* Fixed pickling errors when pickling :class:`AsyncResult` on older Python
* celeryd: prefetch count was decremented by eta tasks even if there
were no active prefetch limits.
.. _version-2.1.2:
:release-data: TBA
.. _v212-fixes:
* celeryd: Now sends the `task-retried` event for retried tasks.
* celeryd: Now honors ignore result for
:exc:`~celery.exceptions.WorkerLostError` and timeout errors.
* celerybeat: Fixed :exc:`UnboundLocalError` in celerybeat logging
when using logging setup signals.
* celeryd: All log messages now includes `exc_info`.
.. _version-2.1.1:
:release-date: 2010-10-14 02:00 P.M CEST
.. _v211-fixes:
* Now working on Windows again.
Removed dependency on the pwd/grp modules.
* snapshots: Fixed race condition leading to loss of events.
* celeryd: Reject tasks with an eta that cannot be converted to a time stamp.
See issue #209
* concurrency.processes.pool: The semaphore was released twice for each task
(both at ACK and result ready).
This has been fixed, and it is now released only once per task.
* docs/configuration: Fixed typo `CELERYD_SOFT_TASK_TIME_LIMIT` ->
See issue #214
* control command `dump_scheduled`: was using old .info attribute
* :program:`celeryd-multi`: Fixed `set changed size during iteration` bug
occurring in the restart command.
* celeryd: Accidentally tried to use additional command line arguments.
This would lead to an error like:
`got multiple values for keyword argument 'concurrency'`.
Additional command line arguments are now ignored, and does not
produce this error. However -- we do reserve the right to use
positional arguments in the future, so please do not depend on this
* celerybeat: Now respects routers and task execution options again.
* celerybeat: Now reuses the publisher instead of the connection.
* Cache result backend: Using :class:`float` as the expires argument
to `cache.set` is deprecated by the memcached libraries,
so we now automatically cast to :class:`int`.
* unit tests: No longer emits logging and warnings in test output.
.. _v211-news:
* Now depends on carrot version 0.10.7.
* Added :setting:`CELERY_REDIRECT_STDOUTS`, and
:setting:`CELERY_REDIRECT_STDOUTS` is used by :program:`celeryd` and
:program:`celerybeat`. All output to `stdout` and `stderr` will be
redirected to the current logger if enabled.
:setting:`CELERY_REDIRECT_STDOUTS_LEVEL` decides the log level used and is
:const:`WARNING` by default.
* Added :setting:`CELERYBEAT_SCHEDULER` setting.
This setting is used to define the default for the -S option to
.. code-block:: python
CELERYBEAT_SCHEDULER = "djcelery.schedulers.DatabaseScheduler"
* Added Task.expires: Used to set default expiry time for tasks.
* New remote control commands: `add_consumer` and `cancel_consumer`.
.. method:: add_consumer(queue, exchange, exchange_type, routing_key,
Tells the worker to declare and consume from the specified
.. method:: cancel_consumer(queue_name)
Tells the worker to stop consuming from queue (by queue name).
Commands also added to :program:`celeryctl` and
Example using celeryctl to start consuming from queue "queue", in
exchange "exchange", of type "direct" using binding key "key"::
$ celeryctl inspect add_consumer queue exchange direct key
$ celeryctl inspect cancel_consumer queue
See :ref:`monitoring-celeryctl` for more information about the
:program:`celeryctl` program.
Another example using :class:`~celery.task.control.inspect`:
.. code-block:: python
>>> from celery.task.control import inspect
>>> inspect.add_consumer(queue="queue", exchange="exchange",
... exchange_type="direct",
... routing_key="key",
... durable=False,
... auto_delete=True)
>>> inspect.cancel_consumer("queue")
* celerybeat: Now logs the traceback if a message can't be sent.
* celerybeat: Now enables a default socket timeout of 30 seconds.
* README/introduction/homepage: Added link to `Flask-Celery`_.
.. _`Flask-Celery`:
.. _version-2.1.0:
:release-date: 2010-10-08 12:00 P.M CEST
.. _v210-important:
Important Notes
* Celery is now following the versioning semantics defined by `semver`_.
This means we are no longer allowed to use odd/even versioning semantics
By our previous versioning scheme this stable release should have
been version 2.2.
.. _`semver`:
* Now depends on Carrot 0.10.7.
* No longer depends on SQLAlchemy, this needs to be installed separately
if the database result backend is used.
* django-celery now comes with a monitor for the Django Admin interface.
This can also be used if you're not a Django user. See
:ref:`monitoring-django-admin` and :ref:`monitoring-nodjango` for more information.
* If you get an error after upgrading saying:
`AttributeError: 'module' object has no attribute 'system'`,
Then this is because the `celery.platform` module has been
renamed to `celery.platforms` to not collide with the built-in
:mod:`platform` module.
You have to remove the old :file:`` (and maybe
:file:`platform.pyc`) file from your previous Celery installation.
To do this use :program:`python` to find the location
of this module::
$ python
>>> import celery.platform
>>> celery.platform
<module 'celery.platform' from '/opt/devel/celery/celery/platform.pyc'>
Here the compiled module is in :file:`/opt/devel/celery/celery/`,
to remove the offending files do::
$ rm -f /opt/devel/celery/celery/*
.. _v210-news:
* Added support for expiration of AMQP results (requires RabbitMQ 2.1.0)
The new configuration option :setting:`CELERY_AMQP_TASK_RESULT_EXPIRES`
sets the expiry time in seconds (can be int or float):
.. code-block:: python
CELERY_AMQP_TASK_RESULT_EXPIRES = 30 * 60 # 30 minutes.
* celeryev: Event Snapshots
If enabled, :program:`celeryd` sends messages about what the worker is doing.
These messages are called "events".
The events are used by real-time monitors to show what the
cluster is doing, but they are not very useful for monitoring
over a longer period of time. Snapshots
lets you take "pictures" of the clusters state at regular intervals.
This can then be stored in a database to generate statistics
with, or even monitoring over longer time periods.
django-celery now comes with a Celery monitor for the Django
Admin interface. To use this you need to run the django-celery
snapshot camera, which stores snapshots to the database at configurable
intervals. See :ref:`monitoring-nodjango` for information about using
this monitor if you're not using Django.
To use the Django admin monitor you need to do the following:
1. Create the new database tables.
$ python syncdb
2. Start the django-celery snapshot camera::
$ python celerycam
3. Open up the django admin to monitor your cluster.
The admin interface shows tasks, worker nodes, and even
lets you perform some actions, like revoking and rate limiting tasks,
and shutting down worker nodes.
There's also a Debian init.d script for :mod:`~celery.bin.celeryev` available,
see :doc:`cookbook/daemonizing` for more information.
New command line arguments to celeryev:
* :option:`-c|--camera`: Snapshot camera class to use.
* :option:`--logfile|-f`: Log file
* :option:`--loglevel|-l`: Log level
* :option:`--maxrate|-r`: Shutter rate limit.
* :option:`--freq|-F`: Shutter frequency
The :option:`--camera` argument is the name of a class used to take
snapshots with. It must support the interface defined by
Shutter frequency controls how often the camera thread wakes up,
while the rate limit controls how often it will actually take
a snapshot.
The rate limit can be an integer (snapshots/s), or a rate limit string
which has the same syntax as the task rate limit strings (`"200/m"`,
`"10/s"`, `"1/h",` etc).
For the Django camera case, this rate limit can be used to control
how often the snapshots are written to the database, and the frequency
used to control how often the thread wakes up to check if there's
anything new.
The rate limit is off by default, which means it will take a snapshot
for every :option:`--frequency` seconds.
.. seealso::
:ref:`monitoring-django-admin` and :ref:`monitoring-snapshots`.
* :func:`~celery.task.control.broadcast`: Added callback argument, this can be
used to process replies immediately as they arrive.
* celeryctl: New command-line utility to manage and inspect worker nodes,
apply tasks and inspect the results of tasks.
.. seealso::
The :ref:`monitoring-celeryctl` section in the :ref:`guide`.
Some examples::
$ celeryctl apply tasks.add -a '[2, 2]' --countdown=10
$ celeryctl inspect active
$ celeryctl inspect registered_tasks
$ celeryctl inspect scheduled
$ celeryctl inspect --help
$ celeryctl apply --help
* Added the ability to set an expiry date and time for tasks.
>>> # Task expires after one minute from now.
>>> task.apply_async(args, kwargs, expires=60)
>>> # Also supports datetime
>>> task.apply_async(args, kwargs,
... + timedelta(days=1)
When a worker receives a task that has been expired it will be
marked as revoked (:exc:`celery.exceptions.TaskRevokedError`).
* Changed the way logging is configured.
We now configure the root logger instead of only configuring
our custom logger. In addition we don't hijack
the multiprocessing logger anymore, but instead use a custom logger name
for different applications:
===================================== =====================================
**Application** **Logger Name**
===================================== =====================================
`celeryd` "celery"
`celerybeat` "celery.beat"
`celeryev` "celery.ev"
===================================== =====================================
This means that the `loglevel` and `logfile` arguments will
affect all registered loggers (even those from 3rd party libraries).
Unless you configure the loggers manually as shown below, that is.
*Users can choose to configure logging by subscribing to the
:signal:`~celery.signals.setup_logging` signal:*
.. code-block:: python
from logging.config import fileConfig
from celery import signals
def setup_logging(**kwargs):
If there are no receivers for this signal, the logging subsystem
will be configured using the :option:`--loglevel`/:option:`--logfile`
argument, this will be used for *all defined loggers*.
Remember that celeryd also redirects stdout and stderr
to the celery logger, if manually configure logging
you also need to redirect the stdouts manually:
.. code-block:: python
from logging.config import fileConfig
from celery import log
def setup_logging(**kwargs):
import logging
stdouts = logging.getLogger("mystdoutslogger")
log.redirect_stdouts_to_logger(stdouts, loglevel=logging.WARNING)
* celeryd: Added command-line option :option:`-I`/:option:`--include`:
A comma separated list of (task) modules to be imported.
$ celeryd -I app1.tasks,app2.tasks
* celeryd: now emits a warning if running as the root user (euid is 0).
* :func:`celery.messaging.establish_connection`: Ability to override defaults
used using keyword argument "defaults".
* celeryd: Now uses `multiprocessing.freeze_support()` so that it should work
with **py2exe**, **PyInstaller**, **cx_Freeze**, etc.
* celeryd: Now includes more metadata for the :state:`STARTED` state: PID and
host name of the worker that started the task.
See issue #181
* subtask: Merge additional keyword arguments to `subtask()` into task keyword
>>> s = subtask((1, 2), {"foo": "bar"}, baz=1)
>>> s.args
(1, 2)
>>> s.kwargs
{"foo": "bar", "baz": 1}
See issue #182.
* celeryd: Now emits a warning if there is already a worker node using the same
name running on the same virtual host.
* AMQP result backend: Sending of results are now retried if the connection
is down.
* AMQP result backend: `result.get()`: Wait for next state if state is not
in :data:`~celery.states.READY_STATES`.
* TaskSetResult now supports subscription.
>>> res = TaskSet(tasks).apply_async()
>>> res[0].get()
* Added `Task.send_error_emails` + `Task.error_whitelist`, so these can
be configured per task instead of just by the global setting.
* Added `Task.store_errors_even_if_ignored`, so it can be changed per Task,
not just by the global setting.
* The crontab scheduler no longer wakes up every second, but implements
`remaining_estimate` (*Optimization*).
* celeryd: Store :state:`FAILURE` result if the
:exc:`~celery.exceptions.WorkerLostError` exception occurs (worker process
* celeryd: Store :state:`FAILURE` result if one of the `*TimeLimitExceeded`
exceptions occurs.
* Refactored the periodic task responsible for cleaning up results.
* The backend cleanup task is now only added to the schedule if
* If the schedule already contains a periodic task named
"celery.backend_cleanup" it won't change it, so the behavior of the
backend cleanup task can be easily changed.
* The task is now run every day at 4:00 AM, rather than every day since
the first time it was run (using crontab schedule instead of
* Renamed `celery.task.builtins.DeleteExpiredTaskMetaTask`
-> :class:`celery.task.builtins.backend_cleanup`
* The task itself has been renamed from "celery.delete_expired_task_meta"
to "celery.backend_cleanup"
See issue #134.
* Implemented `AsyncResult.forget` for sqla/cache/redis/tyrant backends.
(Forget and remove task result).
See issue #184.
* :meth:`TaskSetResult.join <celery.result.TaskSetResult.join>`:
Added 'propagate=True' argument.
When set to :const:`False` exceptions occurring in subtasks will
not be re-raised.
* Added `Task.update_state(task_id, state, meta)`
as a shortcut to `task.backend.store_result(task_id, meta, state)`.
The backend interface is "private" and the terminology outdated,
so better to move this to :class:`~celery.task.base.Task` so it can be
* timer2: Set `self.running=False` in
:meth:`~celery.utils.timer2.Timer.stop` so it won't try to join again on
subsequent calls to `stop()`.
* Log colors are now disabled by default on Windows.
* `celery.platform` renamed to :mod:`celery.platforms`, so it doesn't
collide with the built-in :mod:`platform` module.
* Exceptions occurring in Mediator+Pool callbacks are now caught and logged
instead of taking down the worker.
* Redis result backend: Now supports result expiration using the Redis
`EXPIRE` command.
* unit tests: Don't leave threads running at tear down.
* celeryd: Task results shown in logs are now truncated to 46 chars.
* `Task.__name__` is now an alias to `self.__class__.__name__`.
This way tasks introspects more like regular functions.
* `Task.retry`: Now raises :exc:`TypeError` if kwargs argument is empty.
See issue #164.
* timedelta_seconds: Use `timedelta.total_seconds` if running on Python 2.7
* :class:`~celery.datastructures.TokenBucket`: Generic Token Bucket algorithm
* :mod:``: Recording of cluster state can now
be paused and resumed, including support for buffering.
.. method:: State.freeze(buffer=True)
Pauses recording of the stream.
If `buffer` is true, events received while being frozen will be
buffered, and may be replayed later.
.. method:: State.thaw(replay=True)
Resumes recording of the stream.
If `replay` is true, then the recorded buffer will be applied.
.. method:: State.freeze_while(fun)
With a function to apply, freezes the stream before,
and replays the buffer after the function returns.
* :meth:`EventReceiver.capture <>`
Now supports a timeout keyword argument.
* celeryd: The mediator thread is now disabled if
:setting:`CELERY_RATE_LIMITS` is enabled, and tasks are directly sent to the
pool without going through the ready queue (*Optimization*).
.. _v210-fixes:
* Pool: Process timed out by `TimeoutHandler` must be joined by the Supervisor,
so don't remove it from the internal process list.
See issue #192.
* `TaskPublisher.delay_task` now supports exchange argument, so exchange can be
overridden when sending tasks in bulk using the same publisher
See issue #187.
* celeryd no longer marks tasks as revoked if :setting:`CELERY_IGNORE_RESULT`
is enabled.
See issue #207.
* AMQP Result backend: Fixed bug with `result.get()` if
:setting:`CELERY_TRACK_STARTED` enabled.
`result.get()` would stop consuming after receiving the
:state:`STARTED` state.
* Fixed bug where new processes created by the pool supervisor becomes stuck
while reading from the task Queue.
* Fixed timing issue when declaring the remote control command reply queue
This issue could result in replies being lost, but have now been fixed.
* Backward compatible `LoggerAdapter` implementation: Now works for Python 2.4.
Also added support for several new methods:
`fatal`, `makeRecord`, `_log`, `log`, `isEnabledFor`,
`addHandler`, `removeHandler`.
.. _v210-experimental:
* celeryd-multi: Added daemonization support.
celeryd-multi can now be used to start, stop and restart worker nodes.
$ celeryd-multi start jerry elaine george kramer
This also creates PID files and log files (:file:``,
..., :file:`celeryd@jerry.log`. To specify a location for these files
use the `--pidfile` and `--logfile` arguments with the `%n`
$ celeryd-multi start jerry elaine george kramer \
--logfile=/var/log/celeryd@%n.log \
$ celeryd-multi stop jerry elaine george kramer
Restarting. The nodes will be restarted one by one as the old ones
are shutdown::
$ celeryd-multi restart jerry elaine george kramer
Killing the nodes (**WARNING**: Will discard currently executing tasks)::
$ celeryd-multi kill jerry elaine george kramer
See `celeryd-multi help` for help.
* celeryd-multi: `start` command renamed to `show`.
`celeryd-multi start` will now actually start and detach worker nodes.
To just generate the commands you have to use `celeryd-multi show`.
* celeryd: Added `--pidfile` argument.
The worker will write its pid when it starts. The worker will
not be started if this file exists and the pid contained is still alive.
* Added generic init.d script using `celeryd-multi`
.. _v210-documentation:
* Added User guide section: Monitoring
* Added user guide section: Periodic Tasks
Moved from `getting-started/periodic-tasks` and updated.
* tutorials/external moved to new section: "community".
* References has been added to all sections in the documentation.
This makes it easier to link between documents.
.. _version-2.0.3:
:release-date: 2010-08-27 12:00 P.M CEST
.. _v203-fixes:
* celeryd: Properly handle connection errors happening while
closing consumers.
* celeryd: Events are now buffered if the connection is down,
then sent when the connection is re-established.
* No longer depends on the :mod:`mailer` package.
This package had a name space collision with `django-mailer`,
so its functionality was replaced.
* Redis result backend: Documentation typos: Redis doesn't have
database names, but database numbers. The default database is now 0.
* :class:`~celery.task.control.inspect`:
`registered_tasks` was requesting an invalid command because of a typo.
See issue #170.
* :setting:`CELERY_ROUTES`: Values defined in the route should now have
precedence over values defined in :setting:`CELERY_QUEUES` when merging
the two.
With the follow settings::
CELERY_QUEUES = {"cpubound": {"exchange": "cpubound",
"routing_key": "cpubound"}}
CELERY_ROUTES = {"tasks.add": {"queue": "cpubound",
"routing_key": "tasks.add",
"serializer": "json"}}
The final routing options for `tasks.add` will become::
{"exchange": "cpubound",
"routing_key": "tasks.add",
"serializer": "json"}
This was not the case before: the values
in :setting:`CELERY_QUEUES` would take precedence.
* Worker crashed if the value of :setting:`CELERY_TASK_ERROR_WHITELIST` was
not an iterable
* :func:`~celery.execute.apply`: Make sure `kwargs["task_id"]` is
always set.
* `AsyncResult.traceback`: Now returns :const:`None`, instead of raising
:exc:`KeyError` if traceback is missing.
* :class:`~celery.task.control.inspect`: Replies did not work correctly
if no destination was specified.
* Can now store result/metadata for custom states.
* celeryd: A warning is now emitted if the sending of task error
emails fails.
* celeryev: Curses monitor no longer crashes if the terminal window
is resized.
See issue #160.
* celeryd: On OS X it is not possible to run `os.exec*` in a process
that is threaded.
This breaks the SIGHUP restart handler,
and is now disabled on OS X, emitting a warning instead.
See issue #152.
* :mod:`celery.execute.trace`: Properly handle `raise(str)`,
which is still allowed in Python 2.4.
See issue #175.
* Using urllib2 in a periodic task on OS X crashed because
of the proxy auto detection used in OS X.
This is now fixed by using a workaround.
See issue #143.
* Debian init scripts: Commands should not run in a sub shell
See issue #163.
* Debian init scripts: Use the absolute path of celeryd to allow stat
See issue #162.
.. _v203-documentation:
* getting-started/broker-installation: Fixed typo
`set_permissions ""` -> `set_permissions ".*"`.
* Tasks User Guide: Added section on database transactions.
See issue #169.
* Routing User Guide: Fixed typo `"feed": -> {"queue": "feeds"}`.
See issue #169.
* Documented the default values for the :setting:`CELERYD_CONCURRENCY`
and :setting:`CELERYD_PREFETCH_MULTIPLIER` settings.
* Tasks User Guide: Fixed typos in the subtask example
* celery.signals: Documented worker_process_init.
* Daemonization cookbook: Need to export DJANGO_SETTINGS_MODULE in
* Added some more FAQs from stack overflow
* Daemonization cookbook: Fixed typo `CELERYD_LOGFILE/CELERYD_PIDFILE`
Also added troubleshooting section for the init scripts.
.. _version-2.0.2:
:release-date: 2010-07-22 11:31 A.M CEST
* Routes: When using the dict route syntax, the exchange for a task
could disappear making the task unroutable.
See issue #158.
* Test suite now passing on Python 2.4
* No longer have to type `PYTHONPATH=.` to use celeryconfig in the current
This is accomplished by the default loader ensuring that the current
directory is in `sys.path` when loading the config module.
`sys.path` is reset to its original state after loading.
Adding the current working directory to `sys.path` without the user
knowing may be a security issue, as this means someone can drop a Python module in the users
directory that executes arbitrary commands. This was the original reason
not to do this, but if done *only when loading the config module*, this
means that the behavior will only apply to the modules imported in the
config module, which I think is a good compromise (certainly better than
just explicitly setting `PYTHONPATH=.` anyway)
* Experimental Cassandra backend added.
* celeryd: SIGHUP handler accidentally propagated to worker pool processes.
In combination with 7a7c44e39344789f11b5346e9cc8340f5fe4846c
this would make each child process start a new celeryd when
the terminal window was closed :/
* celeryd: Do not install SIGHUP handler if running from a terminal.
This fixes the problem where celeryd is launched in the background
when closing the terminal.
* celeryd: Now joins threads at shutdown.
See issue #152.
* Test tear down: Don't use `atexit` but nose's `teardown()` functionality
See issue #154.
* Debian init script for celeryd: Stop now works correctly.
* Task logger: `warn` method added (synonym for `warning`)
* Can now define a white list of errors to send error emails for.
CELERY_TASK_ERROR_WHITELIST = ('myapp.MalformedInputError')
See issue #153.
* celeryd: Now handles overflow exceptions in `time.mktime` while parsing
the ETA field.
* LoggerWrapper: Try to detect loggers logging back to stderr/stdout making
an infinite loop.
* Added :class:`celery.task.control.inspect`: Inspects a running worker.
# Inspect a single worker
>>> i = inspect("")
# Inspect several workers
>>> i = inspect(["", ""])
# Inspect all workers consuming on this vhost.
>>> i = inspect()
### Methods
# Get currently executing tasks
# Get currently reserved tasks
>>> i.reserved()
# Get the current eta schedule
>>> i.scheduled()
# Worker statistics and info
>>> i.stats()
# List of currently revoked tasks
>>> i.revoked()
# List of registered tasks
>>> i.registered_tasks()
* Remote control commands `dump_active`/`dump_reserved`/`dump_schedule`
now replies with detailed task requests.
Containing the original arguments and fields of the task requested.
In addition the remote control command `set_loglevel` has been added,
this only changes the log level for the main process.
* Worker control command execution now catches errors and returns their
string representation in the reply.
* Functional test suite added
:mod:`` contains utilities to start
and stop an embedded celeryd process, for use in functional testing.
.. _version-2.0.1:
:release-date: 2010-07-09 03:02 P.M CEST
* multiprocessing.pool: Now handles encoding errors, so that pickling errors
doesn't crash the worker processes.
* The remote control command replies was not working with RabbitMQ 1.8.0's
stricter equivalence checks.
If you've already hit this problem you may have to delete the
$ camqadm exchange.delete celerycrq
$ python camqadm exchange.delete celerycrq
* A bug sneaked in the ETA scheduler that made it only able to execute
one task per second(!)
The scheduler sleeps between iterations so it doesn't consume too much CPU.
It keeps a list of the scheduled items sorted by time, at each iteration
it sleeps for the remaining time of the item with the nearest deadline.
If there are no eta tasks it will sleep for a minimum amount of time, one
second by default.
A bug sneaked in here, making it sleep for one second for every task
that was scheduled. This has been fixed, so now it should move
tasks like hot knife through butter.
In addition a new setting has been added to control the minimum sleep
interval; :setting:`CELERYD_ETA_SCHEDULER_PRECISION`. A good
value for this would be a float between 0 and 1, depending
on the needed precision. A value of 0.8 means that when the ETA of a task
is met, it will take at most 0.8 seconds for the task to be moved to the
ready queue.
* Pool: Supervisor did not release the semaphore.
This would lead to a deadlock if all workers terminated prematurely.
* Added Python version trove classifiers: 2.4, 2.5, 2.6 and 2.7
* Tests now passing on Python 2.7.
* Task.__reduce__: Tasks created using the task decorator can now be pickled.
* nose added to `tests_require`.
* Pickle should now work with SQLAlchemy 0.5.x
* New homepage design by Jan Henrik Helmers:
* New Sphinx theme by Armin Ronacher:
* Fixed "pending_xref" errors shown in the HTML rendering of the
documentation. Apparently this was caused by new changes in Sphinx 1.0b2.
* Router classes in :setting:`CELERY_ROUTES` are now imported lazily.
Importing a router class in a module that also loads the Celery
environment would cause a circular dependency. This is solved
by importing it when needed after the environment is set up.
* :setting:`CELERY_ROUTES` was broken if set to a single dict.
This example in the docs should now work again::
CELERY_ROUTES = {"feed.tasks.import_feed": "feeds"}
* `CREATE_MISSING_QUEUES` was not honored by apply_async.
* New remote control command: `stats`
Dumps information about the worker, like pool process ids, and
total number of tasks executed by type.
Example reply::
'total': {'tasks.sleeptask': 6},
'pool': {'timeouts': [None, None],
'processes': [60376, 60377],
'max-concurrency': 2,
'max-tasks-per-child': None,
'put-guarded-by-semaphore': True}}]
* New remote control command: `dump_active`
Gives a list of tasks currently being executed by the worker.
By default arguments are passed through repr in case there
are arguments that is not JSON encodable. If you know
the arguments are JSON safe, you can pass the argument `safe=True`.
Example reply::
>>> broadcast("dump_active", arguments={"safe": False}, reply=True)
[{'worker.local': [
{'args': '(1,)',
'time_start': 1278580542.6300001,
'name': 'tasks.sleeptask',
'delivery_info': {
'consumer_tag': '30',
'routing_key': 'celery',
'exchange': 'celery'},
'hostname': 'casper.local',
'acknowledged': True,
'kwargs': '{}',
'id': '802e93e9-e470-47ed-b913-06de8510aca2',
* Added experimental support for persistent revokes.
Use the `-S|--statedb` argument to celeryd to enable it::
$ celeryd --statedb=/var/run/celeryd
This will use the file: `/var/run/celeryd.db`,
as the `shelve` module automatically adds the `.db` suffix.
.. _version-2.0.0:
:release-date: 2010-07-02 02:30 P.M CEST
Celery 2.0 contains backward incompatible changes, the most important
being that the Django dependency has been removed so Celery no longer
supports Django out of the box, but instead as an add-on package
called `django-celery`_.
We're very sorry for breaking backwards compatibility, but there's
also many new and exciting features to make up for the time you lose
upgrading, so be sure to read the :ref:`News <v200-news>` section.
Quite a lot of potential users have been upset about the Django dependency,
so maybe this is a chance to get wider adoption by the Python community as
Big thanks to all contributors, testers and users!
.. _v200-django-upgrade:
Upgrading for Django-users
Django integration has been moved to a separate package: `django-celery`_.
* To upgrade you need to install the `django-celery`_ module and change::
INSTALLED_APPS = "djcelery"
* If you use `mod_wsgi` you need to add the following line to your `.wsgi`
import os
os.environ["CELERY_LOADER"] = "django"
* The following modules has been moved to `django-celery`_:
===================================== =====================================
**Module name** **Replace with**
===================================== =====================================
`celery.models` `djcelery.models`
`celery.managers` `djcelery.managers`
`celery.views` `djcelery.views`
`celery.urls` `djcelery.urls`
`` ``
`celery.loaders.djangoapp` `djcelery.loaders`
`celery.backends.database` `djcelery.backends.database`
`celery.backends.cache` `djcelery.backends.cache`
===================================== =====================================
Importing :mod:`djcelery` will automatically setup Celery to use Django loader.
loader. It does this by setting the :envvar:`CELERY_LOADER` environment variable to
`"django"` (it won't change it if a loader is already set.)
When the Django loader is used, the "database" and "cache" result backend
aliases will point to the :mod:`djcelery` backends instead of the built-in backends,
and configuration will be read from the Django settings.
.. _`django-celery`:
.. _v200-upgrade:
Upgrading for others
.. _v200-upgrade-database:
Database result backend
The database result backend is now using `SQLAlchemy`_ instead of the
Django ORM, see `Supported Databases`_ for a table of supported databases.
The `DATABASE_*` settings has been replaced by a single setting:
:setting:`CELERY_RESULT_DBURI`. The value here should be an
`SQLAlchemy Connection String`_, some examples include:
.. code-block:: python
# sqlite (filename)
CELERY_RESULT_DBURI = "sqlite:///celerydb.sqlite"
# mysql
CELERY_RESULT_DBURI = "mysql://scott:tiger@localhost/foo"
# postgresql
CELERY_RESULT_DBURI = "postgresql://scott:tiger@localhost/mydatabase"
# oracle
CELERY_RESULT_DBURI = "oracle://scott:tiger@"
See `SQLAlchemy Connection Strings`_ for more information about connection
To specify additional SQLAlchemy database engine options you can use
the :setting:`CELERY_RESULT_ENGINE_OPTIONS` setting::
# echo enables verbose logging from SQLAlchemy.
.. _`SQLAlchemy`:
.. _`Supported Databases`:
.. _`SQLAlchemy Connection String`:
.. _`SQLAlchemy Connection Strings`:
.. _v200-upgrade-cache:
Cache result backend
The cache result backend is no longer using the Django cache framework,
but it supports mostly the same configuration syntax::
CELERY_CACHE_BACKEND = "memcached://;"
To use the cache backend you must either have the `pylibmc`_ or
`python-memcached`_ library installed, of which the former is regarded
as the best choice.
.. _`pylibmc`:
.. _`python-memcached`:
The support backend types are `memcached://` and `memory://`,
we haven't felt the need to support any of the other backends
provided by Django.
.. _v200-incompatible:
Backward incompatible changes
* Default (python) loader now prints warning on missing ``
instead of raising :exc:`ImportError`.
celeryd raises :exc:`~celery.exceptions.ImproperlyConfigured` if the configuration
is not set up. This makes it possible to use `--help` etc., without having a
working configuration.
Also this makes it possible to use the client side of celery without being
>>> from carrot.connection import BrokerConnection
>>> conn = BrokerConnection("localhost", "guest", "guest", "/")
>>> from celery.execute import send_task
>>> r = send_task("", args=(), kwargs={}, connection=conn)
>>> from celery.backends.amqp import AMQPBackend
>>> r.backend = AMQPBackend(connection=conn)
>>> r.get()
* The following deprecated settings has been removed (as scheduled by
the `deprecation timeline`_):
===================================== =====================================
**Setting name** **Replace with**
===================================== =====================================
===================================== =====================================
.. _`deprecation timeline`:
* The `` module has been removed, use :mod:`celery.task.http`
instead (as scheduled by the `deprecation timeline`_).
* It's no longer allowed to skip the class name in loader names.
(as scheduled by the `deprecation timeline`_):
Assuming the implicit `Loader` class name is no longer supported,
if you use e.g.::
CELERY_LOADER = "myapp.loaders"
You need to include the loader class name, like this::
CELERY_LOADER = "myapp.loaders.Loader"
* :setting:`CELERY_TASK_RESULT_EXPIRES` now defaults to 1 day.
Previous default setting was to expire in 5 days.
* AMQP backend: Don't use different values for `auto_delete`.
This bug became visible with RabbitMQ 1.8.0, which no longer
allows conflicting declarations for the auto_delete and durable settings.
If you've already used celery with this backend chances are you
have to delete the previous declaration::
$ camqadm exchange.delete celeryresults
* Now uses pickle instead of cPickle on Python versions <= 2.5
cPickle is broken in Python <= 2.5.
It unsafely and incorrectly uses relative instead of absolute imports,
so e.g.::
Your best choice is to upgrade to Python 2.6,
as while the pure pickle version has worse performance,
it is the only safe option for older Python versions.
.. _v200-news:
* **celeryev**: Curses Celery Monitor and Event Viewer.
This is a simple monitor allowing you to see what tasks are
executing in real-time and investigate tracebacks and results of ready
tasks. It also enables you to set new rate limits and revoke tasks.
.. figure:: images/celeryevshotsm.jpg
If you run `celeryev` with the `-d` switch it will act as an event
dumper, simply dumping the events it receives to standard out::
$ celeryev -d
-> celeryev: starting capture...
casper.local [2010-06-04 10:42:07.020000] heartbeat
casper.local [2010-06-04 10:42:14.750000] task received:
tasks.add(61a68756-27f4-4879-b816-3cf815672b0e) args=[2, 2] kwargs={}
eta=2010-06-04T10:42:16.669290, retries=0
casper.local [2010-06-04 10:42:17.230000] task started
tasks.add(61a68756-27f4-4879-b816-3cf815672b0e) args=[2, 2] kwargs={}
casper.local [2010-06-04 10:42:17.960000] task succeeded:
args=[2, 2] kwargs={} result=4, runtime=0.782663106918
The fields here are, in order: *sender hostname*, *timestamp*, *event type* and
*additional event fields*.
* AMQP result backend: Now supports `.ready()`, `.successful()`,
`.result`, `.status`, and even responds to changes in task state
* New user guides:
* :doc:`userguide/workers`
* :doc:`userguide/tasksets`
* :doc:`userguide/routing`
* celeryd: Standard out/error is now being redirected to the log file.
* :mod:`billiard` has been moved back to the celery repository.
===================================== =====================================
**Module name** **celery equivalent**
===================================== =====================================
`billiard.pool` `celery.concurrency.processes.pool`
`billiard.serialization` `celery.serialization`
`billiard.utils.functional` `celery.utils.functional`
===================================== =====================================
The :mod:`billiard` distribution may be maintained, depending on interest.
* now depends on :mod:`carrot` >= 0.10.5
* now depends on :mod:`pyparsing`
* celeryd: Added `--purge` as an alias to `--discard`.
* celeryd: Ctrl+C (SIGINT) once does warm shutdown, hitting Ctrl+C twice
forces termination.
* Added support for using complex crontab-expressions in periodic tasks. For
example, you can now use::
>>> crontab(minute="*/15")
or even::
>>> crontab(minute="*/30", hour="8-17,1-2", day_of_week="thu-fri")
See :doc:`userguide/periodic-tasks`.
* celeryd: Now waits for available pool processes before applying new
tasks to the pool.
This means it doesn't have to wait for dozens of tasks to finish at shutdown
because it has applied prefetched tasks without having any pool
processes available to immediately accept them.
See issue #122.
* New built-in way to do task callbacks using
See :doc:`userguide/tasksets` for more information.
* TaskSets can now contain several types of tasks.
:class:`~celery.task.sets.TaskSet` has been refactored to use
a new syntax, please see :doc:`userguide/tasksets` for more information.
The previous syntax is still supported, but will be deprecated in
version 1.4.
* TaskSet failed() result was incorrect.
See issue #132.
* Now creates different loggers per task class.
See issue #129.
* Missing queue definitions are now created automatically.
You can disable this using the :setting:`CELERY_CREATE_MISSING_QUEUES`
The missing queues are created with the following options::
CELERY_QUEUES[name] = {"exchange": name,
"exchange_type": "direct",
"routing_key": "name}
This feature is added for easily setting up routing using the `-Q`
option to `celeryd`::
$ celeryd -Q video, image
See the new routing section of the User Guide for more information:
* New Task option: `Task.queue`
If set, message options will be taken from the corresponding entry
in :setting:`CELERY_QUEUES`. `exchange`, `exchange_type` and `routing_key`
will be ignored
* Added support for task soft and hard time limits.
New settings added:
Hard time limit. The worker processing the task will be killed and
replaced with a new one when this is exceeded.
Soft time limit. The :exc:`celery.exceptions.SoftTimeLimitExceeded`
exception will be raised when this is exceeded. The task can catch
this to e.g. clean up before the hard time limit comes.
New command line arguments to celeryd added:
`--time-limit` and `--soft-time-limit`.
What's left?
This won't work on platforms not supporting signals (and specifically
the `SIGUSR1` signal) yet. So an alternative the ability to disable
the feature all together on nonconforming platforms must be implemented.
Also when the hard time limit is exceeded, the task result should
be a `TimeLimitExceeded` exception.
* Test suite is now passing without a running broker, using the carrot
in-memory backend.
* Log output is now available in colors.
===================================== =====================================
**Log level** **Color**
===================================== =====================================
`DEBUG` Blue
`WARNING` Yellow
`CRITICAL` Magenta
===================================== =====================================
This is only enabled when the log output is a tty.
You can explicitly enable/disable this feature using the
:setting:`CELERYD_LOG_COLOR` setting.
* Added support for task router classes (like the django multi-db routers)
* New setting: :setting:`CELERY_ROUTES`
This is a single, or a list of routers to traverse when
sending tasks. Dictionaries in this list converts to a
:class:`celery.routes.MapRoute` instance.
>>> CELERY_ROUTES = {"": "default",
"mytasks.add": "cpu-bound",
"video.encode": {
"queue": "video",
"exchange": "media"
"routing_key": ""}}
>>> CELERY_ROUTES = ("myapp.tasks.Router",
{"": "default})
Where `myapp.tasks.Router` could be:
.. code-block:: python
class Router(object):
def route_for_task(self, task, args=None, kwargs=None):
if task == "":
return "default"
route_for_task may return a string or a dict. A string then means
it's a queue name in :setting:`CELERY_QUEUES`, a dict means it's a custom route.
When sending tasks, the routers are consulted in order. The first
router that doesn't return `None` is the route to use. The message options
is then merged with the found route settings, where the routers settings
have priority.
Example if :func:`~celery.execute.apply_async` has these arguments::
>>> Task.apply_async(immediate=False, exchange="video",
... routing_key="video.compress")
and a router returns::
{"immediate": True,
"exchange": "urgent"}
the final message options will be::
immediate=True, exchange="urgent", routing_key="video.compress"
(and any default message options defined in the
:class:`~celery.task.base.Task` class)
* New Task handler called after the task returns:
* :class:`~celery.datastructures.ExceptionInfo` now passed to
:meth:`~celery.task.base.Task.on_failure` as einfo keyword argument.
* celeryd: Added :setting:`CELERYD_MAX_TASKS_PER_CHILD` /
Defines the maximum number of tasks a pool worker can process before
the process is terminated and replaced by a new one.
* Revoked tasks now marked with state :state:`REVOKED`, and `result.get()`
will now raise :exc:`~celery.exceptions.TaskRevokedError`.
* :func:`` now works as expected.
* `apply(throw=True)` / :setting:`CELERY_EAGER_PROPAGATES_EXCEPTIONS`:
Makes eager execution re-raise task errors.
* New signal: :signal:`~celery.signals.worker_process_init`: Sent inside the
pool worker process at init.
* celeryd :option:`-Q` option: Ability to specify list of queues to use,
disabling other configured queues.
For example, if :setting:`CELERY_QUEUES` defines four
queues: `image`, `video`, `data` and `default`, the following
command would make celeryd only consume from the `image` and `video`
$ celeryd -Q image,video
* celeryd: New return value for the `revoke` control command:
Now returns::
{"ok": "task $id revoked"}
instead of `True`.
* celeryd: Can now enable/disable events using remote control
Example usage:
>>> from celery.task.control import broadcast
>>> broadcast("enable_events")
>>> broadcast("disable_events")
* Removed top-level tests directory. Test config now in celery.tests.config
This means running the unit tests doesn't require any special setup.
`celery/tests/__init__` now configures the :envvar:`CELERY_CONFIG_MODULE`
and :envvar:`CELERY_LOADER` environment variables, so when `nosetests`
imports that, the unit test environment is all set up.
Before you run the tests you need to install the test requirements::
$ pip install -r contrib/requirements/test.txt
Running all tests::
$ nosetests
Specifying the tests to run::
$ nosetests celery.tests.test_task
Producing HTML coverage::
$ nosetests --with-coverage3
The coverage output is then located in `celery/tests/cover/index.html`.
* celeryd: New option `--version`: Dump version info and exit.
* :mod:`celeryd-multi <celeryd.bin.celeryd_multi>`: Tool for shell scripts
to start multiple workers.
Some examples::
# Advanced example with 10 workers:
# * Three of the workers processes the images and video queue
# * Two of the workers processes the data queue with loglevel DEBUG
# * the rest processes the default' queue.
$ celeryd-multi start 10 -l INFO -Q:1-3 images,video -Q:4,5:data
-Q default -L:4,5 DEBUG
# get commands to start 10 workers, with 3 processes each
$ celeryd-multi start 3 -c 3
celeryd -n celeryd1.myhost -c 3
celeryd -n celeryd2.myhost -c 3
celeryd- n celeryd3.myhost -c 3
# start 3 named workers
$ celeryd-multi start image video data -c 3
celeryd -n image.myhost -c 3
celeryd -n video.myhost -c 3
celeryd -n data.myhost -c 3
# specify custom hostname
$ celeryd-multi start 2 -n -c 3
celeryd -n -c 3
celeryd -n -c 3
# Additionl options are added to each celeryd',
# but you can also modify the options for ranges of or single workers
# 3 workers: Two with 3 processes, and one with 10 processes.
$ celeryd-multi start 3 -c 3 -c:1 10
celeryd -n celeryd1.myhost -c 10
celeryd -n celeryd2.myhost -c 3
celeryd -n celeryd3.myhost -c 3
# can also specify options for named workers
$ celeryd-multi start image video data -c 3 -c:image 10
celeryd -n image.myhost -c 10
celeryd -n video.myhost -c 3
celeryd -n data.myhost -c 3
# ranges and lists of workers in options is also allowed:
# (-c:1-3 can also be written as -c:1,2,3)
$ celeryd-multi start 5 -c 3 -c:1-3 10
celeryd-multi -n celeryd1.myhost -c 10
celeryd-multi -n celeryd2.myhost -c 10
celeryd-multi -n celeryd3.myhost -c 10
celeryd-multi -n celeryd4.myhost -c 3
celeryd-multi -n celeryd5.myhost -c 3
# lists also works with named workers
$ celeryd-multi start foo bar baz xuzzy -c 3 -c:foo,bar,baz 10
celeryd-multi -n foo.myhost -c 10
celeryd-multi -n bar.myhost -c 10
celeryd-multi -n baz.myhost -c 10
celeryd-multi -n xuzzy.myhost -c 3
* The worker now calls the result backends `process_cleanup` method
*after* task execution instead of before.
* AMQP result backend now supports Pika.
.. _version-1.0.6:
:release-date: 2010-06-30 09:57 A.M CEST
* RabbitMQ 1.8.0 has extended their exchange equivalence tests to
include `auto_delete` and `durable`. This broke the AMQP backend.
If you've already used the AMQP backend this means you have to
delete the previous definitions::
$ camqadm exchange.delete celeryresults
$ python camqadm exchange.delete celeryresults
.. _version-1.0.5:
:release-date: 2010-06-01 02:36 P.M CEST
.. _v105-critical:
* SIGINT/Ctrl+C killed the pool, abruptly terminating the currently executing
Fixed by making the pool worker processes ignore :const:`SIGINT`.
* Should not close the consumers before the pool is terminated, just cancel
the consumers.
See issue #122.
* Now depends on :mod:`billiard` >= 0.3.1
* celeryd: Previously exceptions raised by worker components could stall startup,
now it correctly logs the exceptions and shuts down.
* celeryd: Prefetch counts was set too late. QoS is now set as early as possible,
so celeryd can't slurp in all the messages at start-up.
.. _v105-changes:
* :mod:`celery.contrib.abortable`: Abortable tasks.
Tasks that defines steps of execution, the task can then
be aborted after each step has completed.
* :class:``: No longer creates AMQP channel
if events are disabled
* Added required RPM package names under `[bdist_rpm]` section, to support building RPMs
from the sources using
* Running unit tests: :envvar:`NOSE_VERBOSE` environment var now enables verbose output from Nose.
* :func:`celery.execute.apply`: Pass log file/log level arguments as task kwargs.
See issue #110.
* celery.execute.apply: Should return exception, not :class:`~celery.datastructures.ExceptionInfo`
on error.
See issue #111.
* Added new entries to the :doc:`FAQs <faq>`:
* Should I use retry or acks_late?
* Can I execute a task by name?
.. _version-1.0.4:
:release-date: 2010-05-31 09:54 A.M CEST
* Changelog merged with 1.0.5 as the release was never announced.
.. _version-1.0.3:
:release-date: 2010-05-15 03:00 P.M CEST
.. _v103-important:
Important notes
* Messages are now acknowledged *just before* the task function is executed.
This is the behavior we've wanted all along, but couldn't have because of
limitations in the multiprocessing module.
The previous behavior was not good, and the situation worsened with the
release of 1.0.1, so this change will definitely improve
reliability, performance and operations in general.
For more information please see
* Database result backend: result now explicitly sets `null=True` as
`django-picklefield` version 0.1.5 changed the default behavior
right under our noses :(
This means those who created their celery tables (via syncdb or
celeryinit) with picklefield versions >= 0.1.5 has to alter their tables to
allow the result field to be `NULL` manually.
ALTER TABLE celery_taskmeta MODIFY result TEXT NULL
* Removed `Task.rate_limit_queue_type`, as it was not really useful
and made it harder to refactor some parts.
* Now depends on carrot >= 0.10.4
* Now depends on billiard >= 0.3.0
.. _v103-news:
* AMQP backend: Added timeout support for `result.get()` /
* New task option: `Task.acks_late` (default: :setting:`CELERY_ACKS_LATE`)
Late ack means the task messages will be acknowledged **after** the task
has been executed, not *just before*, which is the default behavior.
.. note::
This means the tasks may be executed twice if the worker
crashes in mid-execution. Not acceptable for most
applications, but desirable for others.
* Added crontab-like scheduling to periodic tasks.
Like a cron job, you can specify units of time of when
you would like the task to execute. While not a full implementation
of cron's features, it should provide a fair degree of common scheduling
You can specify a minute (0-59), an hour (0-23), and/or a day of the
week (0-6 where 0 is Sunday, or by names: sun, mon, tue, wed, thu, fri,
.. code-block:: python
from celery.schedules import crontab
from celery.decorators import periodic_task
@periodic_task(run_every=crontab(hour=7, minute=30))
def every_morning():
print("Runs every morning at 7:30a.m")
@periodic_task(run_every=crontab(hour=7, minute=30, day_of_week="mon"))
def every_monday_morning():
print("Run every monday morning at 7:30a.m")
def every_hour():
print("Runs every hour on the clock. e.g. 1:30, 2:30, 3:30 etc.")
.. note::
This a late addition. While we have unittests, due to the
nature of this feature we haven't been able to completely test this
in practice, so consider this experimental.
* `TaskPool.apply_async`: Now supports the `accept_callback` argument.
* `apply_async`: Now raises :exc:`ValueError` if task args is not a list,
or kwargs is not a tuple (Issue #95).
* `Task.max_retries` can now be `None`, which means it will retry forever.
* Celerybeat: Now reuses the same connection when publishing large
sets of tasks.
* Modified the task locking example in the documentation to use
`cache.add` for atomic locking.
* Added experimental support for a *started* status on tasks.
If `Task.track_started` is enabled the task will report its status
as "started" when the task is executed by a worker.
The default value is `False` as the normal behaviour is to not
report that level of granularity. Tasks are either pending, finished,
or waiting to be retried. Having a "started" status can be useful for
when there are long running tasks and there is a need to report which
task is currently running.
The global default can be overridden by the :setting:`CELERY_TRACK_STARTED`
* User Guide: New section `Tips and Best Practices`.
Contributions welcome!
.. _v103-remote-control:
Remote control commands
* Remote control commands can now send replies back to the caller.
Existing commands has been improved to send replies, and the client
interface in `celery.task.control` has new keyword arguments: `reply`,
`timeout` and `limit`. Where reply means it will wait for replies,
timeout is the time in seconds to stop waiting for replies, and limit
is the maximum number of replies to get.
By default, it will wait for as many replies as possible for one second.
* rate_limit(task_name, destination=all, reply=False, timeout=1, limit=0)
Worker returns `{"ok": message}` on success,
or `{"failure": message}` on failure.
>>> from celery.task.control import rate_limit
>>> rate_limit("tasks.add", "10/s", reply=True)
[{'worker1': {'ok': 'new rate limit set successfully'}},
{'worker2': {'ok': 'new rate limit set successfully'}}]
* ping(destination=all, reply=False, timeout=1, limit=0)
Worker returns the simple message `"pong"`.
>>> from celery.task.control import ping
>>> ping(reply=True)
[{'worker1': 'pong'},
{'worker2': 'pong'},
* revoke(destination=all, reply=False, timeout=1, limit=0)
Worker simply returns `True`.
>>> from celery.task.control import revoke
>>> revoke("419e46eb-cf6a-4271-86a8-442b7124132c", reply=True)
[{'worker1': True},
{'worker2'; True}]
* You can now add your own remote control commands!
Remote control commands are functions registered in the command
registry. Registering a command is done using
.. code-block:: python
from celery.task.control import Panel
def reset_broker_connection(panel, **kwargs):
return {"ok": "connection re-established"}
With this module imported in the worker, you can launch the command
using `celery.task.control.broadcast`::
>>> from celery.task.control import broadcast
>>> broadcast("reset_broker_connection", reply=True)
[{'worker1': {'ok': 'connection re-established'},
{'worker2': {'ok': 'connection re-established'}}]
**TIP** You can choose the worker(s) to receive the command
by using the `destination` argument::
>>> broadcast("reset_broker_connection", destination=["worker1"])
[{'worker1': {'ok': 'connection re-established'}]
* New remote control command: `dump_reserved`
Dumps tasks reserved by the worker, waiting to be executed::
>>> from celery.task.control import broadcast
>>> broadcast("dump_reserved", reply=True)
[{'myworker1': [<TaskRequest ....>]}]
* New remote control command: `dump_schedule`
Dumps the workers currently registered ETA schedule.
These are tasks with an `eta` (or `countdown`) argument
waiting to be executed by the worker.
>>> from celery.task.control import broadcast
>>> broadcast("dump_schedule", reply=True)
[{'w1': []},
{'w3': []},
{'w2': ['0. 2010-05-12 11:06:00 pri0 <TaskRequest
args:"(<Feeds freq_max:3600 freq_min:60
start:2184.0 stop:3276.0>,)",
kwargs:"{'page': 2}"}>']},
{'w4': ['0. 2010-05-12 11:00:00 pri0 <TaskRequest
args:"(<Feeds freq_max:3600 freq_min:60
start:1092.0 stop:2184.0>,)",
kwargs:"{\'page\': 1}"}>',
'1. 2010-05-12 11:12:00 pri0 <TaskRequest
args:"(<Feeds freq_max:3600 freq_min:60
start:3276.0 stop:4365>,)",
kwargs:"{\'page\': 3}"}>']}]
.. _v103-fixes:
* Mediator thread no longer blocks for more than 1 second.
With rate limits enabled and when there was a lot of remaining time,
the mediator thread could block shutdown (and potentially block other
jobs from coming in).
* Remote rate limits was not properly applied (Issue #98).
* Now handles exceptions with Unicode messages correctly in
* Database backend: `TaskMeta.result`: default value should be `None`
not empty string.
.. _version-1.0.2:
:release-date: 2010-03-31 12:50 P.M CET
* Deprecated: :setting:`CELERY_BACKEND`, please use
:setting:`CELERY_RESULT_BACKEND` instead.
* We now use a custom logger in tasks. This logger supports task magic
keyword arguments in formats.
The default format for tasks (:setting:`CELERYD_TASK_LOG_FORMAT`) now
includes the id and the name of tasks so the origin of task log messages
can easily be traced.
Example output::
[2010-03-25 13:11:20,317: INFO/PoolWorker-1]
[tasks.add(a6e1c5ad-60d9-42a0-8b24-9e39363125a4)] Hello from add
To revert to the previous behavior you can set::
[%(asctime)s: %(levelname)s/%(processName)s] %(message)s
* Unit tests: Don't disable the django test database tear down,
instead fixed the underlying issue which was caused by modifications
to the `DATABASE_NAME` setting (Issue #82).
* Django Loader: New config :setting:`CELERY_DB_REUSE_MAX` (max number of
tasks to reuse the same database connection)
The default is to use a new connection for every task.
We would very much like to reuse the connection, but a safe number of
reuses is not known, and we don't have any way to handle the errors
that might happen, which may even be database dependent.
* celeryd: The worker components are now configurable: :setting:`CELERYD_POOL`,
:setting:`CELERYD_CONSUMER`, :setting:`CELERYD_MEDIATOR`, and
The default configuration is as follows:
.. code-block:: python
CELERYD_POOL = "celery.concurrency.processes.TaskPool"
CELERYD_MEDIATOR = "celery.worker.controllers.Mediator"
CELERYD_ETA_SCHEDULER = "celery.worker.controllers.ScheduleController"
CELERYD_CONSUMER = "celery.worker.consumer.Consumer"
The :setting:`CELERYD_POOL` setting makes it easy to swap out the
multiprocessing pool with a threaded pool, or how about a
twisted/eventlet pool?
Consider the competition for the first pool plug-in started!
* Debian init scripts: Use `-a` not `&&` (Issue #82).
* Debian init scripts: Now always preserves `$CELERYD_OPTS` from the
`/etc/default/celeryd` and `/etc/default/celerybeat`.
* celery.beat.Scheduler: Fixed a bug where the schedule was not properly
flushed to disk if the schedule had not been properly initialized.
* celerybeat: Now syncs the schedule to disk when receiving the :sig:`SIGTERM`
and :sig:`SIGINT` signals.
* Control commands: Make sure keywords arguments are not in Unicode.
* ETA scheduler: Was missing a logger object, so the scheduler crashed
when trying to log that a task had been revoked.
* management.commands.camqadm: Fixed typo `camqpadm` -> `camqadm`
(Issue #83).
* PeriodicTask.delta_resolution: Was not working for days and hours, now fixed
by rounding to the nearest day/hour.
* Fixed a potential infinite loop in `BaseAsyncResult.__eq__`, although
there is no evidence that it has ever been triggered.
* celeryd: Now handles messages with encoding problems by acking them and
emitting an error message.
.. _version-1.0.1:
:release-date: 2010-02-24 07:05 P.M CET
* Tasks are now acknowledged early instead of late.
This is done because messages can only be acknowledged within the same
connection channel, so if the connection is lost we would have to refetch
the message again to acknowledge it.
This might or might not affect you, but mostly those running tasks with a
really long execution time are affected, as all tasks that has made it
all the way into the pool needs to be executed before the worker can
safely terminate (this is at most the number of pool workers, multiplied
by the :setting:`CELERYD_PREFETCH_MULTIPLIER` setting.)
We multiply the prefetch count by default to increase the performance at
times with bursts of tasks with a short execution time. If this doesn't
apply to your use case, you should be able to set the prefetch multiplier
to zero, without sacrificing performance.
.. note::
A patch to :mod:`multiprocessing` is currently being
worked on, this patch would enable us to use a better solution, and is
scheduled for inclusion in the `2.0.0` release.
* celeryd now shutdowns cleanly when receiving the :sig:`SIGTERM` signal.
* celeryd now does a cold shutdown if the :sig:`SIGINT` signal is received (Ctrl+C),
this means it tries to terminate as soon as possible.
* Caching of results now moved to the base backend classes, so no need
to implement this functionality in the base classes.
* Caches are now also limited in size, so their memory usage doesn't grow
out of control.
You can set the maximum number of results the cache
can hold using the :setting:`CELERY_MAX_CACHED_RESULTS` setting (the
default is five thousand results). In addition, you can refetch already
retrieved results using `backend.reload_task_result` +
`backend.reload_taskset_result` (that's for those who want to send
results incrementally).
* `celeryd` now works on Windows again.
.. warning::
If you're using Celery with Django, you can't use `project.settings`
as the settings module name, but the following should work::
$ python celeryd --settings=settings
* Execution: `.messaging.TaskPublisher.send_task` now
incorporates all the functionality apply_async previously did.
Like converting countdowns to eta, so :func:`celery.execute.apply_async` is
now simply a convenient front-end to
:meth:`celery.messaging.TaskPublisher.send_task`, using
the task classes default options.
Also :func:`celery.execute.send_task` has been
introduced, which can apply tasks using just the task name (useful
if the client does not have the destination task in its task registry).
>>> from celery.execute import send_task
>>> result = send_task("", args=[], kwargs={})
>>> result.get()
* `camqadm`: This is a new utility for command line access to the AMQP API.
Excellent for deleting queues/bindings/exchanges, experimentation and
$ camqadm
1> help
Gives an interactive shell, type `help` for a list of commands.
When using Django, use the management command instead::
$ python camqadm
1> help
* Redis result backend: To conform to recent Redis API changes, the following
settings has been deprecated:
These will emit a `DeprecationWarning` if used.
A `REDIS_PASSWORD` setting has been added, so you can use the new
simple authentication mechanism in Redis.
* The redis result backend no longer calls `SAVE` when disconnecting,
as this is apparently better handled by Redis itself.
* If `settings.DEBUG` is on, celeryd now warns about the possible
memory leak it can result in.
* The ETA scheduler now sleeps at most two seconds between iterations.
* The ETA scheduler now deletes any revoked tasks it might encounter.
As revokes are not yet persistent, this is done to make sure the task
is revoked even though it's currently being hold because its eta is e.g.
a week into the future.
* The `task_id` argument is now respected even if the task is executed
eagerly (either using apply, or :setting:`CELERY_ALWAYS_EAGER`).
* The internal queues are now cleared if the connection is reset.
* New magic keyword argument: `delivery_info`.
Used by retry() to resend the task to its original destination using the same
* Events: Fields was not passed by `.send()` (fixes the UUID key errors
in celerymon)
* Added `--schedule`/`-s` option to celeryd, so it is possible to
specify a custom schedule filename when using an embedded celerybeat
server (the `-B`/`--beat`) option.
* Better Python 2.4 compatibility. The test suite now passes.
* task decorators: Now preserve docstring as `cls.__doc__`, (was previously
copied to ``)
* The `testproj` directory has been renamed to `tests` and we're now using
`nose` + `django-nose` for test discovery, and `unittest2` for test
* New pip requirements files available in `contrib/requirements`.
* TaskPublisher: Declarations are now done once (per process).
* Added `Task.delivery_mode` and the :setting:`CELERY_DEFAULT_DELIVERY_MODE`
These can be used to mark messages non-persistent (i.e. so they are
lost if the broker is restarted).
* Now have our own `ImproperlyConfigured` exception, instead of using the
Django one.
* Improvements to the Debian init scripts: Shows an error if the program is
not executable. Does not modify `CELERYD` when using django with
.. _version-1.0.0:
:release-date: 2010-02-10 04:00 P.M CET
.. _v100-incompatible:
Backward incompatible changes
* Celery does not support detaching anymore, so you have to use the tools
available on your platform, or something like Supervisord to make
celeryd/celerybeat/celerymon into background processes.
We've had too many problems with celeryd daemonizing itself, so it was
decided it has to be removed. Example startup scripts has been added to
* Debian, Ubuntu, (start-stop-daemon)
* Mac OS X launchd
* Supervisord (
In addition to `--detach`, the following program arguments has been
removed: `--uid`, `--gid`, `--workdir`, `--chroot`, `--pidfile`,
`--umask`. All good daemonization tools should support equivalent
functionality, so don't worry.
Also the following configuration keys has been removed:
* Default celeryd loglevel is now `WARN`, to enable the previous log level
start celeryd with `--loglevel=INFO`.
* Tasks are automatically registered.
This means you no longer have to register your tasks manually.
You don't have to change your old code right away, as it doesn't matter if
a task is registered twice.
If you don't want your task to be automatically registered you can set
the `abstract` attribute
.. code-block:: python
class MyTask(Task):
abstract = True
By using `abstract` only tasks subclassing this task will be automatically
registered (this works like the Django ORM).
If you don't want subclasses to be registered either, you can set the
`autoregister` attribute to `False`.
Incidentally, this change also fixes the problems with automatic name
assignment and relative imports. So you also don't have to specify a task name
anymore if you use relative imports.
* You can no longer use regular functions as tasks.
This change was added
because it makes the internals a lot more clean and simple. However, you can
now turn functions into tasks by using the `@task` decorator:
.. code-block:: python
from celery.decorators import task
def add(x, y):
return x + y
.. seealso::
:ref:`guide-tasks` for more information about the task decorators.
* The periodic task system has been rewritten to a centralized solution.
This means `celeryd` no longer schedules periodic tasks by default,
but a new daemon has been introduced: `celerybeat`.
To launch the periodic task scheduler you have to run celerybeat::
$ celerybeat
Make sure this is running on one server only, if you run it twice, all
periodic tasks will also be executed twice.
If you only have one worker server you can embed it into celeryd like this::
$ celeryd --beat # Embed celerybeat in celeryd.
* The supervisor has been removed.
This means the `-S` and `--supervised` options to `celeryd` is
no longer supported. Please use something like
* `TaskSet.join` has been removed, use `TaskSetResult.join` instead.
* The task status `"DONE"` has been renamed to `"SUCCESS"`.
* `AsyncResult.is_done` has been removed, use `AsyncResult.successful`
* The worker no longer stores errors if `Task.ignore_result` is set, to
revert to the previous behaviour set
* The statistics functionality has been removed in favor of events,
so the `-S` and --statistics` switches has been removed.
* The module `celery.task.strategy` has been removed.
* `celery.discovery` has been removed, and it's `autodiscover` function is
now in `celery.loaders.djangoapp`. Reason: Internal API.
* The :envvar:`CELERY_LOADER` environment variable now needs loader class name
in addition to module name,
E.g. where you previously had: `"celery.loaders.default"`, you now need
`"celery.loaders.default.Loader"`, using the previous syntax will result
in a `DeprecationWarning`.
* Detecting the loader is now lazy, and so is not done when importing
To make this happen `celery.loaders.settings` has
been renamed to `load_settings` and is now a function returning the
settings object. `celery.loaders.current_loader` is now also
a function, returning the current loader.
loader = current_loader
needs to be changed to::
loader = current_loader()
.. _v100-deprecations:
* The following configuration variables has been renamed and will be
deprecated in v2.0:
* The public API names in celery.conf has also changed to a consistent naming
* We now support consuming from an arbitrary number of queues.
To do this we had to rename the configuration syntax. If you use any of
the custom AMQP routing options (queue/exchange/routing_key, etc.), you
should read the new FAQ entry:
The previous syntax is deprecated and scheduled for removal in v2.0.
* `` has been renamed to `TaskSet.apply_async`.
`` has now been deprecated, and is scheduled for
removal in v2.0.
.. v100-news:
* Rate limiting support (per task type, or globally).
* New periodic task system.
* Automatic registration.
* New cool task decorator syntax.
* celeryd now sends events if enabled with the `-E` argument.
Excellent for monitoring tools, one is already in the making
Current events include: worker-heartbeat,
worker-online, worker-offline.
* You can now delete (revoke) tasks that has already been applied.
* You can now set the hostname celeryd identifies as using the `--hostname`
* Cache backend now respects the :setting:`CELERY_TASK_RESULT_EXPIRES` setting.
* Message format has been standardized and now uses ISO-8601 format
for dates instead of datetime.
* `celeryd` now responds to the :sig:`SIGHUP` signal by restarting itself.
* Periodic tasks are now scheduled on the clock.
I.e. `timedelta(hours=1)` means every hour at :00 minutes, not every
hour from the server starts. To revert to the previous behaviour you
can set `PeriodicTask.relative = True`.
* Now supports passing execute options to a TaskSets list of args, e.g.:
>>> ts = TaskSet(add, [([2, 2], {}, {"countdown": 1}),
... ([4, 4], {}, {"countdown": 2}),
... ([8, 8], {}, {"countdown": 3})])
* Got a 3x performance gain by setting the prefetch count to four times the
concurrency, (from an average task round-trip of 0.1s to 0.03s!).
A new setting has been added: :setting:`CELERYD_PREFETCH_MULTIPLIER`, which
is set to `4` by default.
* Improved support for webhook tasks.
`` is now deprecated, replaced with the new and shiny
:mod:`celery.task.http`. With more reflective names, sensible interface,
and it's possible to override the methods used to perform HTTP requests.
* The results of task sets are now cached by storing it in the result
.. _v100-changes:
* Now depends on carrot >= 0.8.1
* New dependencies: billiard, python-dateutil, django-picklefield
* No longer depends on python-daemon
* The `uuid` distribution is added as a dependency when running Python 2.4.
* Now remembers the previously detected loader by keeping it in
the :envvar:`CELERY_LOADER` environment variable.
This may help on windows where fork emulation is used.
* ETA no longer sends datetime objects, but uses ISO 8601 date format in a
string for better compatibility with other platforms.
* No longer sends error mails for retried tasks.
* Task can now override the backend used to store results.
* Refactored the ExecuteWrapper, `apply` and :setting:`CELERY_ALWAYS_EAGER`
now also executes the task callbacks and signals.
* Now using a proper scheduler for the tasks with an ETA.
This means waiting eta tasks are sorted by time, so we don't have
to poll the whole list all the time.
* Now also imports modules listed in :setting:`CELERY_IMPORTS` when running
with django (as documented).
* Log level for stdout/stderr changed from INFO to ERROR
* ImportErrors are now properly propagated when autodiscovering tasks.
* You can now use `celery.messaging.establish_connection` to establish a
connection to the broker.
* When running as a separate service the periodic task scheduler does some
smart moves to not poll too regularly.
If you need faster poll times you can lower the value
* You can now change periodic task intervals at runtime, by making
`run_every` a property, or subclassing `PeriodicTask.is_due`.
* The worker now supports control commands enabled through the use of a
broadcast queue, you can remotely revoke tasks or set the rate limit for
a task type. See :mod:`celery.task.control`.
* The services now sets informative process names (as shown in `ps`
listings) if the :mod:`setproctitle` module is installed.