Change history

This document contains change notes for bugfix releases in the 3.1.x series (Cipater), please see What’s new in Celery 3.1 (Cipater) for an overview of what’s new in Celery 3.1.

3.1.7

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 RuntimeWarning warning when using the prefork pool, and in 3.2 this will result in an exception being raised.

It’s not legal for tasks to block by waiting for subtasks as this is likely to lead to resource starvation and eventually deadlock when using the prefork pool (see also Avoid launching synchronous subtasks).

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

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 -Ofair option.

Fixes

• Now depends on Kombu 3.0.8.

• Now depends on billiard 3.3.0.13

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

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

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

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

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

  CELERYD_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 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 --logfile, --pidfile and --statedb arguments.

  Example:

  $ 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 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).

3.1.6

• Now depends on billiard 3.3.0.10.

• Now depends on Kombu 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).

3.1.5

• Now depends on Kombu 3.0.6.

• Now depends on 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 /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:

  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).

• 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).

3.1.4

• Now depends on Kombu 3.0.5.

• Now depends on 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.

3.1.3

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

  unpack_from started supporting memoryview arguments in Python 2.7.6.

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

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

3.1.2

• Now depends on 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.

3.1.1

• Now depends on 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 DJANGO_SETTINGS_MODULE so that it doesn’t have to be typed in with the celery command.

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

  Thanks to Chris Ward, orarbel.

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

• Django: 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.

3.1.0

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