celery/docs/history/changelog-3.1.rst

.. _changelog-3.1:

===============================
 Change history for Celery 3.1
===============================

This document contains change notes for bugfix releases in the 3.1.x series
(Cipater), please see :ref:`whatsnew-3.1` for an overview of what's
new in Celery 3.1.

If you're looking for versions prior to 3.1.x you should go to :ref:`history`.

.. _version-3.1.17:

3.1.17
======

.. admonition:: CELERYD_FORCE_EXECV should not be used.

    Please disable this option if you're using the RabbitMQ or Redis
    transports.

    Keeping this option enabled in 3.1 means the async based worker will
    be disabled, so using is more likely to lead to trouble than doing
    anything good.

- **Requirements**

    - Now depends on :ref:`Kombu 3.0.24 <kombu:version-3.0.24>`.

    - Now depends on :mod:`billiard` 3.3.0.19.

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

- **Task**: Raising :exc:`~celery.exceptions.Ignore` no longer sends
  ``task-failed`` event (Issue #2365).

- **Redis result backend**: Fixed errors about unbound local ``self``.

    Fix contributed by Thomas French.

- **Task**: Callbacks was not called properly if ``link`` was a list of
  signatures (Issuse #2350).

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

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

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

    Fix contributed by kristaps.

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

    Fix contributed by Albert Wang.

- **Cassandra result backend**: Fixed problems when using detailed mode.

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

    Fix contributed by Gino Ledesma.

- **Task**: Exception info was not properly set for tasks raising
  :exc:`~celery.exceptions.Reject` (Issue #2043).

- **Worker**: The set of revokes tasks are now deduplicated when loading from
  the worker state database (Issue #2336).

- **celery.contrib.rdb**: Fixed problems with ``rdb.set_trace`` calling stop
  from the wrong frame.

    Fix contributed by llllllllll.

- **Canvas**: ``chain`` and ``chord`` can now be immutable.

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

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

- **Logging**: The ``processName`` format was introduced in Py2.6.2 so for
  compatibility this format is now excluded when using earlier versions
  (Issue #1644).

.. _version-3.1.16:

3.1.16
======
:release-date: 2014-10-03 06:00 P.M UTC
:release-by: Ask Solem

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

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

- **Canvas**: ``celery.signature`` now properly forwards app argument
  in all cases.

- **Task**: ``.retry()`` did not raise the exception correctly
  when called without a current exception.

    Fix contributed by Andrea Rabbaglietti.

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

    Fix contributed by Konstantinos Koukopoulos.

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

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

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

.. _version-3.1.15:

3.1.15
======
:release-date: 2014-09-14 11:00 P.M UTC
:release-by: Ask Solem

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

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

.. _version-3.1.14:

3.1.14
======
:release-date: 2014-09-08 03:00 P.M UTC
:release-by: Ask Solem

- **Requirements**

    - Now depends on :ref:`Kombu 3.0.22 <kombu:version-3.0.22>`.

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

- **Init scripts**: The generic beat script now implements the ``status``
   command.

    Contributed by John Whitlock.

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

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

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

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

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

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


.. _version-3.1.13:

3.1.13
======

Security Fixes
--------------

* [Security: `CELERYSA-0002`_] Insecure default umask.

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

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

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

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

.. _`CELERYSA-0002`:
    http://github.com/celery/celery/tree/master/docs/sec/CELERYSA-0002.txt

News
----

- **Requirements**

    - Now depends on :ref:`Kombu 3.0.21 <kombu:version-3.0.21>`.

    - Now depends on :mod:`billiard` 3.3.0.18.


- **App**: ``backend`` argument now also sets the :setting:`CELERY_RESULT_BACKEND`
  setting.

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

- **Task**: ``retry`` will no longer attempt to requeue the task if sending
  the retry message fails.

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

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

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

- Documentation fixes

    Contributed by Yuval Greenfield, Lucas Wiman, nicholsonjf

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



.. _version-3.1.12:

3.1.12
======
:release-date: 2014-06-09 10:12 P.M UTC
:release-by: Ask Solem

- **Requirements**

    Now depends on :ref:`Kombu 3.0.19 <kombu:version-3.0.19>`.

- **App**: Connections were not being closed after fork due to an error in the
  after fork handler (Issue #2055).

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

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

- **Django**: Fixed problems with event timezones when using Django
  (``Substantial drift``).

    Celery did not take into account that Django modifies the
    ``time.timeone`` attributes and friends.

- **Canvas**: ``Signature.link`` now works when the link option is a scalar
  value (Issue #2019).

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

    Fix contributed by Roger Hu.

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

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

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

    Fix contributed by Illes Solt.

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

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

- **Canvas**: ``signature(s, app=app)`` did not upgrade serialized signatures
  to their original class (``subtask_type``) when the ``app`` keyword argument
  was used.

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

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

    Fix contributed by Alexey Kotlyarov.

- **App**: Fixed strange traceback mangling issue for
  ``app.connection_or_acquire``.

- **Programs**: The :program:`celery multi stopwait` command is now documented
  in usage.

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

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

    Fix contributed by Luke Pomfrey.

- **Other**: The ``inspect conf`` command did not handle non-string keys well.

    Fix contributed by Jay Farrimond.

- **Programs**: Fixed argument handling problem in
  :program:`celery worker --detach`.

    Fix contributed by Dmitry Malinovsky.

- **Programs**: :program:`celery worker --detach` did not forward working
  directory option (Issue #2003).

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

- **Worker**: The ``requires`` attribute for boot steps were not being handled
  correctly (Issue #2002).

- **Eventlet**: The eventlet pool now supports the ``pool_grow`` and
  ``pool_shrink`` remote control commands.

    Contributed by Mher Movsisyan.

- **Eventlet**: The eventlet pool now implements statistics for
  :program:``celery inspect stats``.

    Contributed by Mher Movsisyan.

- **Documentation**: Clarified ``Task.rate_limit`` behavior.

    Contributed by Jonas Haag.

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

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

    Fix contributed by Ian Dees.

- **Init scripts**: The CentOS init scripts did not quote
  :envvar:`CELERY_CHDIR`.

    Fix contributed by ffeast.

.. _version-3.1.11:

3.1.11
======
:release-date: 2014-04-16 11:00 P.M UTC
:release-by: Ask Solem

- **Now compatible with RabbitMQ 3.3.0**

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

    .. code-block:: bash

        $ pip install -U librabbitmq

- **Requirements**:

    - Now depends on :ref:`Kombu 3.0.15 <kombu:version-3.0.15>`.

    - Now depends on `billiard 3.3.0.17`_.

    - Bundle ``celery[librabbitmq]`` now depends on :mod:`librabbitmq` 1.5.0.

.. _`billiard 3.3.0.17`:
    https://github.com/celery/billiard/blob/master/CHANGES.txt

- **Tasks**: The :setting:`CELERY_DEFAULT_DELIVERY_MODE` setting was being
  ignored (Issue #1953).

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

    Contributed by Matthew Duggan and Craig Northway.

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

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

    Fix contributed by Brian Bouterse.

- **Logging**: The color formatter accidentally modified ``record.msg``
  (Issue #1939).

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

- **Results**: ``ResultSet`` now implements a ``.backend`` attribute for
  compatibility with ``AsyncResult``.

- **Results**: ``.forget()`` now also clears the local cache.

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

- **Results**: ``join_native`` populated result cache even if disabled.

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

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

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

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

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


.. _version-3.1.10:

3.1.10
======
:release-date: 2014-03-22 09:40 P.M UTC
:release-by: Ask Solem

- **Requirements**:

    - Now depends on :ref:`Kombu 3.0.14 <kombu:version-3.0.14>`.

- **Results**:

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

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

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

    .. code-block:: python

        BROKER_TRANSPORT_OPTIONS = {'fanout_patterns': True}

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

    See :ref:`redis-caveats`.

    This will be the default in Celery 3.2.

- **Results**: The :class:`@AsyncResult` object now keeps a local cache
  of the final state of the task.

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

- **Events**: The "Substantial drift" warning message is now logged once
  per node name only (Issue #1802).

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

    This can be enabled by using the new ``%i`` and ``%I`` format specifiers
    for the log file name.  See :ref:`worker-files-process-index`.

- **Redis**: New experimental chord join implementation.

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

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

        CELERY_RESULT_BACKEND = 'redis://localhost?new_join=1'

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

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

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

    .. code-block:: bash

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

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

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

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

- **App**: Fixed error message for :meth:`~@Celery.config_from_envvar`.

    Fix contributed by Dmitry Malinovsky.

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

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

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

- **Canvas**: Worker now also logs chord errors.

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

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

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

    Fix contributed by Ionel Cristian Mărieș.

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

- **Task**: ``Task.apply`` now properly sets ``request.headers``
  (Issue #1874).

- **Worker**: Fixed ``UnicodeEncodeError`` occuring when worker is started
  by `supervisord`.

    Fix contributed by Codeb Fan.

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

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

    Contributed by Chris Clark.

- **Commands**: :program:`celery inspect memdump` no longer crashes
  if the :mod:`psutil` module is not installed (Issue #1914).

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

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


.. _version-3.1.9:

3.1.9
=====
:release-date: 2014-02-10 06:43 P.M UTC
:release-by: Ask Solem

- **Requirements**:

    - Now depends on :ref:`Kombu 3.0.12 <kombu:version-3.0.12>`.

- **Prefork pool**: Better handling of exiting child processes.

    Fix contributed by Ionel Cristian Mărieș.

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

    Fix contributed by Ionel Cristian Mărieș.

- **New Sphinx extension**: for autodoc documentation of tasks:
  :mod:`celery.contrib.spinx` (Issue #1833).

- **Django**: Now works with Django 1.7a1.

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

- **Generic init scripts**: Fixed bug in stop command.

    Fix contributed by Rinat Shigapov.

- **Generic init scripts**: Fixed compatibility with GNU :manpage:`stat`.

    Fix contributed by Paul Kilgo.

- **Generic init scripts**: Fixed compatibility with the minimal
  :program:`dash` shell (Issue #1815).

- **Commands**: The :program:`celery amqp basic.publish` command was not
  working properly.

    Fix contributed by Andrey Voronov.

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

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

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

- **Worker**: Improved error message for message decoding errors.

- **Time**: Now properly parses the `Z` timezone specifier in ISO 8601 date
  strings.

    Fix contributed by Martin Davidsson.

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

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

    Fix contributed by Roger Hu.

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

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

.. _version-3.1.8:

3.1.8
=====
:release-date: 2014-01-17 10:45 P.M UTC
:release-by: Ask Solem

- **Requirements**:

    - Now depends on :ref:`Kombu 3.0.10 <kombu:version-3.0.10>`.

    - Now depends on `billiard 3.3.0.14`_.

.. _`billiard 3.3.0.14`:
    https://github.com/celery/billiard/blob/master/CHANGES.txt

- **Worker**: The event loop was not properly reinitialized at consumer restart
  which would force the worker to continue with a closed ``epoll`` instance on
  Linux, resulting in a crash.

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

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

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

- **Results:** ``ResultSet.iterate`` is now pending deprecation.

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

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

- **Worker**\|eventlet/gevent: A regression caused ``Ctrl+C`` to be ineffective
  for shutdown.

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

    Contributed by Pepijn de Vos.

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

- **Worker**\|gossip: Fixed attribute error occurring when another node leaves.

    Fix contributed by Brodie Rao.

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

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

    .. note::

        Note that upgrading celery will not update the init scripts,
        instead you need to manually copy the improved versions from the
        source distribution:
        https://github.com/celery/celery/tree/3.1/extra/generic-init.d

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

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

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

- **Commands:** The :program:`celery multi` command did not forward command
  line configuration to the target workers.

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

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

    .. code-block:: bash

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

    Fix contributed by Antoine Legrand.

- **Canvas:** ``chain.apply_async()`` now properly forwards execution options.

    Fix contributed by Konstantin Podshumok.

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

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

- **Worker:** The worker now closes all open files on :sig:`SIGHUP` (regression)
  (*Issue #1768*).

    Fix contributed by Brodie Rao

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

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

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

    Contributed by Jon Chen.

- **Commands:** The :program:`celery inspect conf` utility now works.

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

- **App:** Fixed rare bug with ``autodiscover_tasks()`` (*Issue #1797*).

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

- **Documentation:** Supervisord examples contained an extraneous '-' in a
  `--logfile` argument example.

    Fix contributed by Mohammad Almeer.

.. _version-3.1.7:

3.1.7
=====
:release-date: 2013-12-17 06:00 P.M UTC
:release-by: Ask Solem

.. _v317-important:

Important Notes
---------------

Init script security improvements
---------------------------------

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

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

You have to upgrade the init scripts manually from this directory:
https://github.com/celery/celery/tree/3.1/extra/generic-init.d

AMQP result backend
~~~~~~~~~~~~~~~~~~~

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

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

    CELERY_RESULT_PERSISTENT = True

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

Synchronous subtasks
~~~~~~~~~~~~~~~~~~~~

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

It's not legal for tasks to block by waiting for subtasks
as this is likely to lead to resource starvation and eventually
deadlock when using the prefork pool (see also :ref:`task-synchronous-subtasks`).

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

.. code-block:: python

    from celery.result import allow_join_result

    @app.task
    def misbehaving():
        result = other_task.delay()
        with allow_join_result():
            result.get()

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

.. _v317-fixes:

Fixes
-----

- Now depends on :ref:`Kombu 3.0.8 <kombu:version-3.0.8>`.

- Now depends on :mod:`billiard` 3.3.0.13

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

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

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

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

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

    .. code-block:: bash

        CELERYD_NODES="X1 X2 Y1 Y2"
        CELERYD_OPTS="-A:X1 x -A:X2 x -A:Y1 y -A:Y2 y"

- Fallback chord unlock task is now always called after the chord header
  (Issue #1700).

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

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

    Fix contributed by Konstantin Podshumok.

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

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

    Fix contributed by Ionel Cristian Mărieș.

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

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

    Example:

    .. code-block:: bash

        $ celery -A proj worker -n foo@%h --logfile=%n.log --statedb=%n.db

- Redis/Cache result backends: Will now timeout if keys evicted while trying
  to join a chord.

- The fallbock unlock chord task now raises :exc:`Retry` so that the
  retry even is properly logged by the worker.

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

- Redis result backend: Now supports UNIX sockets.

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

    Contributed by Alcides Viamontes Esquivel.

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

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

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

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

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

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

.. _version-3.1.6:

3.1.6
=====
:release-date: 2013-12-02 06:00 P.M UTC
:release-by: Ask Solem

- Now depends on :mod:`billiard` 3.3.0.10.

- Now depends on :ref:`Kombu 3.0.7 <kombu:version-3.0.7>`.

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

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

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

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

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

        @task(throws=(KeyError, HttpNotFound))

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

    - Expected errors (included in ``Task.throws``)

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

    - Unexpected errors

        Will be logged using severity ``ERROR``, with traceback included.

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

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

    Fix contributed by Jonathan Jordan.

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

    Fix contributed by Mher Movsisyan.

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

    Fix contributed by Markus Ullmann.

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

- Task: Fixed problem with eta and timezones.

    Fix contributed by Alexander Koval.

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

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

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

- Fixed a compatibility issue with non-abstract task classes

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

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

    Fix contributed by Nick Johnson.

- Fixed Python 2.6 compatibility (Issue #1679).

.. _version-3.1.5:

3.1.5
=====
:release-date: 2013-11-21 06:20 P.M UTC
:release-by: Ask Solem

- Now depends on :ref:`Kombu 3.0.6 <kombu:version-3.0.6>`.

- Now depends on :mod:`billiard` 3.3.0.8

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

- App: ``autodiscover_tasks`` is now lazy.

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

        app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)

    this ensures that the settings object is not prepared
    prematurely.

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

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

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

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

- ``celery.VERSION`` is now a named tuple.

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

- ``celery shell`` command: Fixed ``IPython.frontend`` deprecation warning.

- The default app no longer includes the builtin fixups.

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

- The Django daemonization tutorial was changed.

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

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

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

- App: New ``autofinalize`` option.

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

    Example:

    .. code-block:: python

        app = Celery(autofinalize=False)

        # raises RuntimeError
        tasks = app.tasks

        @app.task
        def add(x, y):
            return x + y

        # raises RuntimeError
        add.delay(2, 2)

        app.finalize()
        # no longer raises:
        tasks = app.tasks
        add.delay(2, 2)

- The worker did not send monitoring events during shutdown.

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

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

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

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

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

- Beat: Fixed syntax error in string formatting.

    Contributed by nadad.

- Fixed typos in the documentation.

    Fixes contributed by Loic Bistuer, sunfinite.

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

.. _version-3.1.4:

3.1.4
=====
:release-date: 2013-11-15 11:40 P.M UTC
:release-by: Ask Solem

- Now depends on :ref:`Kombu 3.0.5 <kombu:version-3.0.5>`.

- Now depends on :mod:`billiard` 3.3.0.7

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

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

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

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

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

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

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

    Fix contributed by Vsevolod.

- Tests now passing on PyPy 2.1 and 2.2.

.. _version-3.1.3:

3.1.3
=====
:release-date: 2013-11-13 00:55 A.M UTC
:release-by: Ask Solem

- Fixed compatibility problem with Python 2.7.0 - 2.7.5 (Issue #1637)

    ``unpack_from`` started supporting ``memoryview`` arguments
    in Python 2.7.6.

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

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

.. _version-3.1.2:

3.1.2
=====
:release-date: 2013-11-12 08:00 P.M UTC
:release-by: Ask Solem

- Now depends on :mod:`billiard` 3.3.0.6

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

- The worker silently ignored task errors.

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

    Fix contributed by j0hnsmith

- Prefork pool: Now using ``_multiprocessing.read`` with ``memoryview``
  if available.

- ``close_open_fds`` now uses ``os.closerange`` if available.

- ``get_fdmax`` now takes value from ``sysconfig`` if possible.

.. _version-3.1.1:

3.1.1
=====
:release-date: 2013-11-11 06:30 P.M UTC
:release-by: Ask Solem

- Now depends on :mod:`billiard` 3.3.0.4.

- Python 3: Fixed compatibility issues.

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

- Django: Tutorial updated with a solution that sets a default
  :envvar:`DJANGO_SETTINGS_MODULE` so that it doesn't have to be typed
  in with the :program:`celery` command.

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

    Thanks to Chris Ward, orarbel.

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

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

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

- Worker: Fixed compatibility with billiard without C extension.

- Inspect.conf: Now supports a ``with_defaults`` argument.

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

.. _version-3.1.0:

3.1.0
=======
:release-date: 2013-11-09 11:00 P.M UTC
:release-by: Ask Solem

See :ref:`whatsnew-3.1`.