whatsnew-4.0.rst 43 KB

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  1. .. _whatsnew-4.0:
  2. ===========================================
  3. What's new in Celery 4.0 (0Today8)
  4. ===========================================
  5. :Author: Ask Solem (``ask at celeryproject.org``)
  6. .. sidebar:: Change history
  7. What's new documents describe the changes in major versions,
  8. we also have a :ref:`changelog` that lists the changes in bugfix
  9. releases (0.0.x), while older series are archived under the :ref:`history`
  10. section.
  11. Celery is a simple, flexible and reliable distributed system to
  12. process vast amounts of messages, while providing operations with
  13. the tools required to maintain such a system.
  14. It's a task queue with focus on real-time processing, while also
  15. supporting task scheduling.
  16. Celery has a large and diverse community of users and contributors,
  17. you should come join us :ref:`on IRC <irc-channel>`
  18. or :ref:`our mailing-list <mailing-list>`.
  19. To read more about Celery you should go read the :ref:`introduction <intro>`.
  20. While this version is backward compatible with previous versions
  21. it's important that you read the following section.
  22. This version is officially supported on CPython 2.7, 3.4 and 3.5.
  23. and also supported on PyPy.
  24. .. _`website`: http://celeryproject.org/
  25. .. topic:: Table of Contents
  26. Make sure you read the important notes before upgrading to this version.
  27. .. contents::
  28. :local:
  29. :depth: 2
  30. Preface
  31. =======
  32. Wall of Contributors
  33. --------------------
  34. Aaron McMillin, Adam Renberg, Adrien Guinet, Ahmet Demir, Aitor Gómez-Goiri,
  35. Albert Wang, Alex Koshelev, Alex Rattray, Alex Williams, Alexander Koshelev,
  36. Alexander Lebedev, Alexander Oblovatniy, Alexey Kotlyarov, Ali Bozorgkhan,
  37. Alice Zoë Bevan–McGregor, Allard Hoeve, Alman One, Andrea Rabbaglietti,
  38. Andrea Rosa, Andrei Fokau, Andrew Rodionoff, Andriy Yurchuk,
  39. Aneil Mallavarapu, Areski Belaid, Artyom Koval, Ask Solem, Balthazar Rouberol,
  40. Berker Peksag, Bert Vanderbauwhede, Brian Bouterse, Chris Duryee, Chris Erway,
  41. Chris Harris, Chris Martin, Corey Farwell, Craig Jellick, Cullen Rhodes,
  42. Dallas Marlow, Daniel Wallace, Danilo Bargen, Davanum Srinivas, Dave Smith,
  43. David Baumgold, David Harrigan, David Pravec, Dennis Brakhane, Derek Anderson,
  44. Dmitry Malinovsky, Dudás Ádám, Dustin J. Mitchell, Ed Morley, Fatih Sucu,
  45. Feanil Patel, Felix Schwarz, Fernando Rocha, Flavio Grossi, Frantisek Holop,
  46. Gao Jiangmiao, Gerald Manipon, Gilles Dartiguelongue, Gino Ledesma,
  47. Hank John, Hogni Gylfason, Ilya Georgievsky, Ionel Cristian Mărieș,
  48. James Pulec, Jared Lewis, Jason Veatch, Jasper Bryant-Greene, Jeremy Tillman,
  49. Jocelyn Delalande, Joe Jevnik, John Anderson, John Kirkham, John Whitlock,
  50. Joshua Harlow, Juan Rossi, Justin Patrin, Kai Groner, Kevin Harvey,
  51. Konstantinos Koukopoulos, Kouhei Maeda, Kracekumar Ramaraju,
  52. Krzysztof Bujniewicz, Latitia M. Haskins, Len Buckens, Lorenzo Mancini,
  53. Lucas Wiman, Luke Pomfrey, Marcio Ribeiro, Marin Atanasov Nikolov,
  54. Mark Parncutt, Maxime Vdb, Mher Movsisyan, Michael (:github_user:`michael-k`),
  55. Michael Duane Mooring, Michael Permana, Mickaël Penhard, Mike Attwood,
  56. Morton Fox, Môshe van der Sterre, Nat Williams, Nathan Van Gheem, Nik Nyby,
  57. Omer Katz, Omer Korner, Ori Hoch, Paul Pearce, Paulo Bu, Philip Garnero,
  58. Piotr Maślanka, Radek Czajka, Raghuram Srinivasan, Randy Barlow,
  59. Rodolfo Carvalho, Roger Hu, Rongze Zhu, Ross Deane, Ryan Luckie,
  60. Rémy Greinhofer, Samuel Jaillet, Sergey Azovskov, Sergey Tikhonov,
  61. Seungha Kim, Steve Peak, Sukrit Khera, Tadej Janež, Tewfik Sadaoui,
  62. Thomas French, Thomas Grainger, Tobias Schottdorf, Tocho Tochev,
  63. Valentyn Klindukh, Vic Kumar, Vladimir Bolshakov, Vladimir Gorbunov,
  64. Wayne Chang, Wil Langford, Will Thompson, William King, Yury Selivanov,
  65. Zoran Pavlovic, 許邱翔, :github_user:`allenling`, :github_user:`bee-keeper`,
  66. :github_user:`ffeast`, :github_user:`flyingfoxlee`, :github_user:`gdw2`,
  67. :github_user:`gitaarik`, :github_user:`hankjin`, :github_user:`m-vdb`,
  68. :github_user:`mdk`, :github_user:`nokrik`, :github_user:`ocean1`,
  69. :github_user:`orlo666`, :github_user:`raducc`, :github_user:`wanglei`,
  70. :github_user:`worldexception`.
  71. .. _v400-important:
  72. Important Notes
  73. ===============
  74. Dropped support for Python 2.6
  75. ------------------------------
  76. Celery now requires Python 2.7 or later,
  77. and also drops support for Python 3.3 so supported versions are:
  78. - CPython 2.7
  79. - CPython 3.4
  80. - CPython 3.5
  81. - PyPy 4.0 (``pypy2``)
  82. - PyPy 2.4 (``pypy3``)
  83. - Jython 2.7.0
  84. Lowercase setting names
  85. -----------------------
  86. In the pursuit of beauty all settings have been renamed to be in all
  87. lowercase, and some setting names have been renamed for naming consistency.
  88. This change is fully backwards compatible so you can still use the uppercase
  89. setting names, but we would like you to upgrade as soon as possible and
  90. you can even do so automatically using the :program:`celery upgrade settings`
  91. command:
  92. .. code-block:: console
  93. $ celery upgrade settings proj/settings.py
  94. This command will modify your module in-place to use the new lower-case
  95. names (if you want uppercase with a celery prefix see block below),
  96. and save a backup in :file:`proj/settings.py.orig`.
  97. .. admonition:: For Django users and others who want to keep uppercase names
  98. If you're loading Celery configuration from the Django settings module
  99. then you will want to keep using the uppercase names.
  100. You will also want to use a ``CELERY_`` prefix so that no Celery settings
  101. collide with Django settings used by other apps.
  102. To do this, you will first need to convert your settings file
  103. to use the new consistent naming scheme, and add the prefix to all
  104. Celery related settings:
  105. .. code-block:: console
  106. $ celery upgrade settings --django proj/settings.py
  107. After upgrading the settings file, you need to set the prefix explicitly
  108. in your ``proj/celery.py`` module:
  109. .. code-block:: python
  110. app.config_from_object('django.conf:settings', namespace='CELERY')
  111. You can find the most up to date Django celery integration example
  112. here: :ref:`django-first-steps`.
  113. Note that this will also add a prefix to settings that didn't previously
  114. have one, like ``BROKER_URL``.
  115. Luckily you don't have to manually change the files, as
  116. the :program:`celery upgrade settings --django` program should do the
  117. right thing.
  118. The loader will try to detect if your configuration is using the new format,
  119. and act accordingly, but this also means that you are not allowed to mix and
  120. match new and old setting names, that is unless you provide a value for both
  121. alternatives.
  122. The major difference between previous versions, apart from the lower case
  123. names, are the renaming of some prefixes, like ``celerybeat_`` to ``beat_``,
  124. ``celeryd_`` to ``worker_``.
  125. The ``celery_`` prefix has also been removed, and task related settings
  126. from this name-space is now prefixed by ``task_``, worker related settings
  127. with ``worker_``.
  128. Apart from this most of the settings will be the same in lowercase, apart from
  129. a few special ones:
  130. ===================================== ==========================================================
  131. **Setting name** **Replace with**
  132. ===================================== ==========================================================
  133. ``CELERY_MAX_CACHED_RESULTS`` :setting:`result_cache_max`
  134. ``CELERY_MESSAGE_COMPRESSION`` :setting:`result_compression`/:setting:`task_compression`.
  135. ``CELERY_TASK_RESULT_EXPIRES`` :setting:`result_expires`
  136. ``CELERY_RESULT_DBURI`` :setting:`sqlalchemy_dburi`
  137. ``CELERY_RESULT_ENGINE_OPTIONS`` :setting:`sqlalchemy_engine_options`
  138. ``-*-_DB_SHORT_LIVED_SESSIONS`` :setting:`sqlalchemy_short_lived_sessions`
  139. ``CELERY_RESULT_DB_TABLE_NAMES`` :setting:`sqlalchemy_db_names`
  140. ``CELERY_ACKS_LATE`` :setting:`task_acks_late`
  141. ``CELERY_ALWAYS_EAGER`` :setting:`task_always_eager`
  142. ``CELERY_ANNOTATIONS`` :setting:`task_annotations`
  143. ``CELERY_MESSAGE_COMPRESSION`` :setting:`task_compression`
  144. ``CELERY_CREATE_MISSING_QUEUES`` :setting:`task_create_missing_queues`
  145. ``CELERY_DEFAULT_DELIVERY_MODE`` :setting:`task_default_delivery_mode`
  146. ``CELERY_DEFAULT_EXCHANGE`` :setting:`task_default_exchange`
  147. ``CELERY_DEFAULT_EXCHANGE_TYPE`` :setting:`task_default_exchange_type`
  148. ``CELERY_DEFAULT_QUEUE`` :setting:`task_default_queue`
  149. ``CELERY_DEFAULT_RATE_LIMIT`` :setting:`task_default_rate_limit`
  150. ``CELERY_DEFAULT_ROUTING_KEY`` :setting:`task_default_routing_key`
  151. ``-"-_EAGER_PROPAGATES_EXCEPTIONS`` :setting:`task_eager_propagates`
  152. ``CELERY_IGNORE_RESULT`` :setting:`task_ignore_result`
  153. ``CELERY_TASK_PUBLISH_RETRY`` :setting:`task_publish_retry`
  154. ``CELERY_TASK_PUBLISH_RETRY_POLICY`` :setting:`task_publish_retry_policy`
  155. ``CELERY_QUEUES`` :setting:`task_queues`
  156. ``CELERY_ROUTES`` :setting:`task_routes`
  157. ``CELERY_SEND_TASK_ERROR_EMAILS`` :setting:`task_send_error_emails`
  158. ``CELERY_SEND_TASK_SENT_EVENT`` :setting:`task_send_sent_event`
  159. ``CELERY_TASK_SERIALIZER`` :setting:`task_serializer`
  160. ``CELERYD_TASK_SOFT_TIME_LIMIT`` :setting:`task_soft_time_limit`
  161. ``CELERYD_TASK_TIME_LIMIT`` :setting:`task_time_limit`
  162. ``CELERY_TRACK_STARTED`` :setting:`task_track_started`
  163. ``CELERY_DISABLE_RATE_LIMITS`` :setting:`worker_disable_rate_limits`
  164. ``CELERY_ENABLE_REMOTE_CONTROL`` :setting:`worker_enable_remote_control`
  165. ``CELERYD_SEND_EVENTS`` :setting:`worker_send_task_events`
  166. ===================================== ==========================================================
  167. You can see a full table of the changes in :ref:`conf-old-settings-map`.
  168. JSON is now the default serializer
  169. ----------------------------------
  170. The time has finally come to end the reign of :mod:`pickle` as the default
  171. serialization mechanism, and json is the default serializer starting from this
  172. version.
  173. This change was :ref:`announced with the release of Celery 3.1
  174. <last-version-to-enable-pickle>`.
  175. If you're still depending on :mod:`pickle` being the default serializer,
  176. then you have to configure your app before upgrading to 4.0:
  177. .. code-block:: python
  178. task_serializer = 'pickle'
  179. result_serializer = 'pickle'
  180. accept_content = {'pickle'}
  181. The Task base class no longer automatically register tasks
  182. ----------------------------------------------------------
  183. The :class:`~@Task` class is no longer using a special meta-class
  184. that automatically registers the task in the task registry.
  185. Instead this is now handled by the :class:`@task` decorators.
  186. If you're still using class based tasks, then you need to register
  187. these manually:
  188. .. code-block:: python
  189. class CustomTask(Task):
  190. def run(self):
  191. print('running')
  192. app.tasks.register(CustomTask())
  193. The best practice is to use custom task classes only for overriding
  194. general behavior, and then using the task decorator to realize the task:
  195. .. code-block:: python
  196. @app.task(bind=True, base=CustomTask)
  197. def custom(self):
  198. print('running')
  199. This change also means the ``abstract`` attribute of the task
  200. no longer has any effect.
  201. Task argument checking
  202. ----------------------
  203. The arguments of the task is now verified when calling the task,
  204. even asynchronously:
  205. .. code-block:: pycon
  206. >>> @app.task
  207. ... def add(x, y):
  208. ... return x + y
  209. >>> add.delay(8, 8)
  210. <AsyncResult: f59d71ca-1549-43e0-be41-4e8821a83c0c>
  211. >>> add.delay(8)
  212. Traceback (most recent call last):
  213. File "<stdin>", line 1, in <module>
  214. File "celery/app/task.py", line 376, in delay
  215. return self.apply_async(args, kwargs)
  216. File "celery/app/task.py", line 485, in apply_async
  217. check_arguments(*(args or ()), **(kwargs or {}))
  218. TypeError: add() takes exactly 2 arguments (1 given)
  219. Redis Events not backward compatible
  220. ------------------------------------
  221. The Redis ``fanout_patterns`` and ``fanout_prefix`` transport
  222. options are now enabled by default, which means that workers
  223. running 4.0 cannot see workers running 3.1 on the default configuration,
  224. and vice versa.
  225. This is only related to monitor event messages, the workers should still
  226. execute tasks as normally.
  227. You can avoid this situation by configuring the 3.1 workers (and clients)
  228. to enable these settings, before upgrading to 4.0:
  229. .. code-block:: python
  230. BROKER_TRANSPORT_OPTIONS = {
  231. 'fanout_patterns': True,
  232. 'fanout_prefix': True,
  233. }
  234. Django: Auto-discover now supports Django app configurations
  235. ------------------------------------------------------------
  236. The :meth:`@autodiscover` function can now be called without arguments,
  237. and the Django handler will automatically find your installed apps:
  238. .. code-block:: python
  239. app.autodiscover()
  240. The Django integration :ref:`example in the documentation
  241. <django-first-steps>` has been updated to use the argument-less call.
  242. Worker direct queues no longer use auto-delete.
  243. ===============================================
  244. Workers/clients running 4.0 will no longer be able to send
  245. worker direct messages to worker running older versions, and vice versa.
  246. If you're relying on worker direct messages you should upgrade
  247. your 3.x workers and clients to use the new routing settings first,
  248. by replacing :func:`celery.utils.worker_direct` with this implementation:
  249. .. code-block:: python
  250. from kombu import Exchange, Queue
  251. worker_direct_exchange = Exchange('C.dq2')
  252. def worker_direct(hostname):
  253. return Queue(
  254. '{hostname}.dq2'.format(hostname),
  255. exchange=worker_direct_exchange,
  256. routing_key=hostname,
  257. )
  258. (This feature closed Issue #2492.)
  259. Old command-line programs removed
  260. ---------------------------------
  261. Installing Celery will no longer install the ``celeryd``,
  262. ``celerybeat`` and ``celeryd-multi`` programs.
  263. This was announced with the release of Celery 3.1, but you may still
  264. have scripts pointing to the old names so make sure you update these
  265. to use the new umbrella command:
  266. +-------------------+--------------+-------------------------------------+
  267. | Program | New Status | Replacement |
  268. +===================+==============+=====================================+
  269. | ``celeryd`` | **REMOVED** | :program:`celery worker` |
  270. +-------------------+--------------+-------------------------------------+
  271. | ``celerybeat`` | **REMOVED** | :program:`celery beat` |
  272. +-------------------+--------------+-------------------------------------+
  273. | ``celeryd-multi`` | **REMOVED** | :program:`celery multi` |
  274. +-------------------+--------------+-------------------------------------+
  275. .. _v400-news:
  276. News
  277. ====
  278. New Task Message Protocol
  279. =========================
  280. .. :sha:`e71652d384b1b5df2a4e6145df9f0efb456bc71c`
  281. This version introduces a brand new task message protocol,
  282. the first major change to the protocol since the beginning of the project.
  283. The new protocol is backwards incompatible, so you need to set
  284. the :setting:`task_protocol` configuration option to ``2`` to take advantage:
  285. .. code-block:: python
  286. app = Celery()
  287. app.conf.task_protocol = 2
  288. Using the new protocol is recommended for everybody who don't
  289. need backwards compatibility.
  290. Once enabled task messages sent is unreadable to older versions of Celery.
  291. New protocol highlights
  292. -----------------------
  293. The new protocol fixes many problems with the old one, and enables
  294. some long-requested features:
  295. - Most of the data are now sent as message headers, instead of being
  296. serialized with the message body.
  297. In version 1 of the protocol the worker always had to deserialize
  298. the message to be able to read task meta-data like the task id,
  299. name, etc. This also meant that the worker was forced to double-decode
  300. the data, first deserializing the message on receipt, serializing
  301. the message again to send to child process, then finally the child process
  302. deserializes the message again.
  303. Keeping the meta-data fields in the message headers means the worker
  304. does not actually have to decode the payload before delivering
  305. the task to the child process, and also that it's now possible
  306. for the worker to reroute a task written in a language different
  307. from Python to a different worker.
  308. - A new ``lang`` message header can be used to specify the programming
  309. language the task is written in.
  310. - Worker stores results for internal errors like ``ContentDisallowed``,
  311. and other deserialization errors.
  312. - Worker stores results and sends monitoring events for unregistered
  313. task errors.
  314. - Worker calls callbacks/errbacks even when the result is sent by the
  315. parent process (e.g. :exc:`WorkerLostError` when a child process
  316. terminates, deserialization errors, unregistered tasks).
  317. - A new ``origin`` header contains information about the process sending
  318. the task (worker node-name, or PID and host-name information).
  319. - A new ``shadow`` header allows you to modify the task name used in logs.
  320. This is useful for dispatch like patterns, like a task that calls
  321. any function using pickle (don't do this at home):
  322. .. code-block:: python
  323. from celery import Task
  324. from celery.utils.imports import qualname
  325. class call_as_task(Task):
  326. def shadow_name(self, args, kwargs, options):
  327. return 'call_as_task:{0}'.format(qualname(args[0]))
  328. def run(self, fun, *args, **kwargs):
  329. return fun(*args, **kwargs)
  330. call_as_task = app.tasks.register(call_as_task())
  331. - New ``argsrepr`` and ``kwargsrepr`` fields contain textual representations
  332. of the task arguments (possibly truncated) for use in logs, monitors, etc.
  333. This means the worker does not have to deserialize the message payload
  334. to display the task arguments for informational purposes.
  335. - Chains now use a dedicated ``chain`` field enabling support for chains
  336. of thousands and more tasks.
  337. - New ``parent_id`` and ``root_id`` headers adds information about
  338. a tasks relationship with other tasks.
  339. - ``parent_id`` is the task id of the task that called this task
  340. - ``root_id`` is the first task in the work-flow.
  341. These fields can be used to improve monitors like flower to group
  342. related messages together (like chains, groups, chords, complete
  343. work-flows, etc).
  344. - ``app.TaskProducer`` replaced by :meth:`@amqp.create_task_message`` and
  345. :meth:`@amqp.send_task_message``.
  346. Dividing the responsibilities into creating and sending means that
  347. people who want to send messages using a Python AMQP client directly,
  348. does not have to implement the protocol.
  349. The :meth:`@amqp.create_task_message` method calls either
  350. :meth:`@amqp.as_task_v2`, or :meth:`@amqp.as_task_v1` depending
  351. on the configured task protocol, and returns a special
  352. :class:`~celery.app.amqp.task_message` tuple containing the
  353. headers, properties and body of the task message.
  354. .. seealso::
  355. The new task protocol is documented in full here:
  356. :ref:`message-protocol-task-v2`.
  357. Prefork: Tasks now log from the child process
  358. =============================================
  359. Logging of task success/failure now happens from the child process
  360. actually executing the task, which means that logging utilities
  361. like Sentry can get full information about tasks that fail, including
  362. variables in the traceback.
  363. Prefork: One log-file per child process
  364. =======================================
  365. Init-scrips and :program:`celery multi` now uses the `%I` log file format
  366. option (e.g. :file:`/var/log/celery/%n%I.log`).
  367. This change was necessary to ensure each child
  368. process has a separate log file after moving task logging
  369. to the child process, as multiple processes writing to the same
  370. log file can cause corruption.
  371. You are encouraged to upgrade your init-scripts and
  372. :program:`celery multi` arguments to use this new option.
  373. Configure broker URL for read/write separately.
  374. ===============================================
  375. New :setting:`broker_read_url` and :setting:`broker_write_url` settings
  376. have been added so that separate broker URLs can be provided
  377. for connections used for consuming/publishing.
  378. In addition to the configuration options, two new methods have been
  379. added the app API:
  380. - ``app.connection_for_read()``
  381. - ``app.connection_for_write()``
  382. These should now be used in place of ``app.connection()`` to specify
  383. the intent of the required connection.
  384. .. note::
  385. Two connection pools are available: ``app.pool`` (read), and
  386. ``app.producer_pool`` (write). The latter does not actually give connections
  387. but full :class:`kombu.Producer` instances.
  388. .. code-block:: python
  389. def publish_some_message(app, producer=None):
  390. with app.producer_or_acquire(producer) as producer:
  391. ...
  392. def consume_messages(app, connection=None):
  393. with app.connection_or_acquire(connection) as connection:
  394. ...
  395. Canvas Refactor
  396. ===============
  397. The canvas/work-flow implementation have been heavily refactored
  398. to fix some long outstanding issues.
  399. .. :sha:`d79dcd8e82c5e41f39abd07ffed81ca58052bcd2`
  400. .. :sha:`1e9dd26592eb2b93f1cb16deb771cfc65ab79612`
  401. .. :sha:`e442df61b2ff1fe855881c1e2ff9acc970090f54`
  402. .. :sha:`0673da5c09ac22bdd49ba811c470b73a036ee776`
  403. - Now unrolls groups within groups into a single group (Issue #1509).
  404. - chunks/map/starmap tasks now routes based on the target task
  405. - chords and chains can now be immutable.
  406. - Fixed bug where serialized signatures were not converted back into
  407. signatures (Issue #2078)
  408. Fix contributed by Ross Deane.
  409. - Fixed problem where chains and groups did not work when using JSON
  410. serialization (Issue #2076).
  411. Fix contributed by Ross Deane.
  412. - Creating a chord no longer results in multiple values for keyword
  413. argument 'task_id' (Issue #2225).
  414. Fix contributed by Aneil Mallavarapu
  415. - Fixed issue where the wrong result is returned when a chain
  416. contains a chord as the penultimate task.
  417. Fix contributed by Aneil Mallavarapu
  418. - Special case of ``group(A.s() | group(B.s() | C.s()))`` now works.
  419. - Chain: Fixed bug with incorrect id set when a subtask is also a chain.
  420. - ``group | group`` is now flattened into a single group (Issue #2573).
  421. - Fixed issue where ``group | task`` was not upgrading correctly
  422. to chord (Issue #2922).
  423. Amazon SQS transport now officially supported.
  424. ==============================================
  425. The SQS broker transport has been rewritten to use async I/O and as such
  426. joins RabbitMQ and Redis as officially supported transports.
  427. The new implementation also takes advantage of long polling,
  428. and closes several issues related to using SQS as a broker.
  429. This work was sponsored by Nextdoor.
  430. Schedule tasks based on sunrise, sunset, dawn and dusk.
  431. =======================================================
  432. See :ref:`beat-solar` for more information.
  433. Contributed by Mark Parncutt.
  434. New API for configuring periodic tasks
  435. ======================================
  436. This new API enables you to use signatures when defining periodic tasks,
  437. removing the chance of mistyping task names.
  438. An example of the new API is :ref:`here <beat-entries>`.
  439. .. :sha:`bc18d0859c1570f5eb59f5a969d1d32c63af764b`
  440. .. :sha:`132d8d94d38f4050db876f56a841d5a5e487b25b`
  441. RabbitMQ Priority queue support
  442. ===============================
  443. See :ref:`routing-options-rabbitmq-priorities` for more information.
  444. Contributed by Gerald Manipon.
  445. Prefork: Limit child process resident memory size.
  446. ==================================================
  447. .. :sha:`5cae0e754128750a893524dcba4ae030c414de33`
  448. You can now limit the maximum amount of memory allocated per prefork
  449. pool child process by setting the worker
  450. :option:`--maxmemperchild <celery worker --maxmemperchild>` option,
  451. or the :setting:`worker_max_memory_per_child` setting.
  452. The limit is for RSS/resident memory size and is specified in kilobytes.
  453. A child process having exceeded the limit will be terminated and replaced
  454. with a new process after the currently executing task returns.
  455. See :ref:`worker-maxmemperchild` for more information.
  456. Contributed by Dave Smith.
  457. Redis: Result backend optimization
  458. ==================================
  459. RPC is now using pub/sub for streaming task results.
  460. ----------------------------------------------------
  461. Calling ``result.get()`` when using the Redis result backend
  462. used to be extremely expensive as it was using polling to wait
  463. for the result to become available. A default polling
  464. interval of 0.5 seconds did not help performance, but was
  465. necessary to avoid a spin loop.
  466. The new implementation is using Redis Pub/Sub mechanisms to
  467. publish and retrieve results immediately, greatly improving
  468. task round-trip times.
  469. Contributed by Yaroslav Zhavoronkov and Ask Solem.
  470. New optimized chord join implementation.
  471. ----------------------------------------
  472. This was an experimental feature introduced in Celery 3.1,
  473. that could only be enabled by adding ``?new_join=1`` to the
  474. result backend URL configuration.
  475. We feel that the implementation has been tested thoroughly enough
  476. to be considered stable and enabled by default.
  477. The new implementation greatly reduces the overhead of chords,
  478. and especially with larger chords the performance benefit can be massive.
  479. New Riak result backend Introduced.
  480. ===================================
  481. See :ref:`conf-riak-result-backend` for more information.
  482. Contributed by Gilles Dartiguelongue, Alman One and NoKriK.
  483. New CouchDB result backend introduced.
  484. ======================================
  485. See :ref:`conf-couchdb-result-backend` for more information.
  486. Contributed by Nathan Van Gheem
  487. Brand new Cassandra result backend.
  488. ===================================
  489. A brand new Cassandra backend utilizing the new :pypi:`cassandra-driver`
  490. library is replacing the old result backend which was using the older
  491. :pypi:`pycassa` library.
  492. See :ref:`conf-cassandra-result-backend` for more information.
  493. .. # XXX What changed?
  494. New Elasticsearch result backend introduced.
  495. ============================================
  496. See :ref:`conf-elasticsearch-result-backend` for more information.
  497. Contributed by Ahmet Demir.
  498. New File-system result backend introduced.
  499. ==========================================
  500. See :ref:`conf-filesystem-result-backend` for more information.
  501. Contributed by Môshe van der Sterre.
  502. Event Batching
  503. ==============
  504. Events are now buffered in the worker and sent as a list which reduces
  505. the overhead required to send monitoring events.
  506. For authors of custom event monitors there will be no action
  507. required as long as you're using the Python celery
  508. helpers (:class:`~@events.Receiver`) to implement your monitor.
  509. However, if you're manually receiving event messages you must now account
  510. for batched event messages which differ from normal event messages
  511. in the following way:
  512. - The routing key for a batch of event messages will be set to
  513. ``<event-group>.multi`` where the only batched event group
  514. is currently ``task`` (giving a routing key of ``task.multi``).
  515. - The message body will be a serialized list-of-dictionaries instead
  516. of a dictionary. Each item in the list can be regarded
  517. as a normal event message body.
  518. .. :sha:`03399b4d7c26fb593e61acf34f111b66b340ba4e`
  519. Task.replace
  520. ============
  521. Task.replace changed, removes Task.replace_in_chord.
  522. The two methods had almost the same functionality, but the old
  523. ``Task.replace`` would force the new task to inherit the
  524. callbacks/errbacks of the existing task.
  525. If you replace a node in a tree, then you would not expect the new node to
  526. inherit the children of the old node, so this seems like unexpected
  527. behavior.
  528. So ``self.replace(sig)`` now works for any task, in addition ``sig`` can now
  529. be a group.
  530. Groups are automatically converted to a chord, where the callback
  531. will "accumulate" the results of the group tasks.
  532. A new built-in task (`celery.accumulate` was added for this purpose)
  533. Closes #817
  534. Optimized Beat implementation
  535. =============================
  536. The :program:`celery beat` implementation has been optimized
  537. for millions of periodic tasks by using a heap to schedule entries.
  538. Contributed by Ask Solem and Alexander Koshelev.
  539. Task Auto-retry Decorator
  540. =========================
  541. Writing custom retry handling for exception events is so common
  542. that we now have built-in support for it.
  543. For this a new ``autoretry_for`` argument is now supported by
  544. the task decorators, where you can specify a tuple of exceptions
  545. to automatically retry for.
  546. See :ref:`task-autoretry` for more information.
  547. Contributed by Dmitry Malinovsky.
  548. .. :sha:`75246714dd11e6c463b9dc67f4311690643bff24`
  549. Remote Task Tracebacks
  550. ======================
  551. The new :setting:`task_remote_tracebacks` will make task tracebacks more
  552. useful by injecting the stack of the remote worker.
  553. This feature requires the additional :pypi:`tblib` library.
  554. Contributed by Ionel Cristian Mărieș.
  555. Async Result API
  556. ================
  557. eventlet/gevent drainers, promises, BLA BLA
  558. Closed issue #2529.
  559. In Other News
  560. -------------
  561. - **Requirements**:
  562. - Now depends on :ref:`Kombu 4.0 <kombu:version-4.0>`.
  563. - Now depends on :pypi:`billiard` version 3.5.
  564. - No longer depends on :pypi:`anyjson` :(
  565. - **Tasks**: The "anon-exchange" is now used for simple name-name direct routing.
  566. This increases performance as it completely bypasses the routing table,
  567. in addition it also improves reliability for the Redis broker transport.
  568. - **Tasks**: :setting:`task_routes` can now contain glob patterns and
  569. regexes.
  570. See new examples in :setting:`task_routes` and :ref:`routing-automatic`.
  571. - **Eventlet/Gevent**: Fixed race condition leading to "simultaneous read"
  572. errors (Issue #2812).
  573. - **Programs**: ``%n`` format for :program:`celery multi` is now synonym with
  574. ``%N`` to be consistent with :program:`celery worker`.
  575. - **Programs**: celery inspect/control now supports a new
  576. :option:`--json <celery inspect --json>` option to give output in json format.
  577. - **Programs**: :program:`celery inspect registered` now ignores built-in
  578. tasks.
  579. - **Programs**: New :program:`celery logtool`: Utility for filtering and parsing
  580. celery worker log-files
  581. - **Redis Transport**: The Redis transport now supports the
  582. :setting:`broker_use_ssl` option.
  583. - **Worker**: Worker now only starts the remote control command consumer if the
  584. broker transport used actually supports them.
  585. - **Worker**: Gossip now sets ``x-message-ttl`` for event queue to heartbeat_interval s.
  586. (Issue #2005).
  587. - **Worker**: Now preserves exit code (Issue #2024).
  588. - **Worker**: Log--level for unrecoverable errors changed from ``error`` to
  589. ``critical``.
  590. - **Worker**: Improved rate limiting accuracy.
  591. - **Worker**: Account for missing timezone information in task expires field.
  592. Fix contributed by Albert Wang.
  593. - **Worker**: The worker no longer has a ``Queues`` bootsteps, as it is now
  594. superfluous.
  595. - **Tasks**: New :setting:`task_reject_on_worker_lost` setting, and
  596. :attr:`~@Task.reject_on_worker_lost` task attribute decides what happens
  597. when the child worker process executing a late ack task is terminated.
  598. Contributed by Michael Permana.
  599. - **Worker**: Improvements and fixes for LimitedSet
  600. Getting rid of leaking memory + adding ``minlen`` size of the set:
  601. the minimal residual size of the set after operating for some time.
  602. ``minlen`` items are kept, even if they should have been expired.
  603. Problems with older and even more old code:
  604. #. Heap would tend to grow in some scenarios
  605. (like adding an item multiple times).
  606. #. Adding many items fast would not clean them soon enough (if ever).
  607. #. When talking to other workers, revoked._data was sent, but
  608. it was processed on the other side as iterable.
  609. That means giving those keys new (current)
  610. time-stamp. By doing this workers could recycle
  611. items forever. Combined with 1) and 2), this means that in
  612. large set of workers, you are getting out of memory soon.
  613. All those problems should be fixed now.
  614. This should fix issues #3095, #3086.
  615. Contributed by David Pravec.
  616. - **App**: New signals for app configuration/finalization:
  617. - :data:`app.on_configure <@on_configure>`
  618. - :data:`app.on_after_configure <@on_after_configure>`
  619. - :data:`app.on_after_finalize <@on_after_finalize>`
  620. - **Task**: New task signals for rejected task messages:
  621. - :data:`celery.signals.task_rejected`.
  622. - :data:`celery.signals.task_unknown`.
  623. - **Events**: Event messages now uses the RabbitMQ ``x-message-ttl`` option
  624. to ensure older event messages are discarded.
  625. The default is 5 seconds, but can be changed using the
  626. :setting:`event_queue_ttl` setting.
  627. - **Events**: New :setting:`event_queue_prefix` setting can now be used
  628. to change the default ``celeryev`` queue prefix for event receiver queues.
  629. Contributed by Takeshi Kanemoto.
  630. - **Events**: Event monitors now sets the :setting:`event_queue_expires`
  631. setting by default.
  632. The queues will now expire after 60 seconds after the monitor stops
  633. consuming from it.
  634. - **Canvas**: ``chunks``/``map``/``starmap`` are now routed based on the target task.
  635. - **Canvas**: ``Signature.link`` now works when argument is scalar (not a list)
  636. (Issue #2019).
  637. - **App**: The application can now change how task names are generated using
  638. the :meth:`~@gen_task_name` method.
  639. Contributed by Dmitry Malinovsky.
  640. - **App**: App has new ``app.current_worker_task`` property that
  641. returns the task that is currently being worked on (or :const:`None`).
  642. (Issue #2100).
  643. - **Tasks**: ``Task.subtask`` renamed to ``Task.signature`` with alias.
  644. - **Tasks**: ``Task.subtask_from_request`` renamed to
  645. ``Task.signature_from_request`` with alias.
  646. - **Tasks**: The ``delivery_mode`` attribute for :class:`kombu.Queue` is now
  647. respected (Issue #1953).
  648. - **Tasks**: Routes in :setting:`task-routes` can now specify a
  649. :class:`~kombu.Queue` instance directly.
  650. Example:
  651. .. code-block:: python
  652. task_routes = {'proj.tasks.add': {'queue': Queue('add')}}
  653. - **Tasks**: ``AsyncResult`` now raises :exc:`ValueError` if task_id is None.
  654. (Issue #1996).
  655. - **Tasks**: ``result.get()`` now supports an ``on_message`` argument to set a
  656. callback to be called for every message received.
  657. - **Tasks**: New abstract classes added:
  658. - :class:`~celery.utils.abstract.CallableTask`
  659. Looks like a task.
  660. - :class:`~celery.utils.abstract.CallableSignature`
  661. Looks like a task signature.
  662. - **Programs**: :program:`celery multi` now passes through `%i` and `%I` log
  663. file formats.
  664. - **Programs**: ``%p`` can now be used to expand to the full worker node-name
  665. in log-file/pid-file arguments.
  666. - **Programs**: A new command line option
  667. :option:`--executable <celery worker --executable>` is now
  668. available for daemonizing programs (:program:`celery worker` and
  669. :program:`celery beat`).
  670. Contributed by Bert Vanderbauwhede.
  671. - **Programs**: :program:`celery worker` supports new
  672. :option:`--prefetch-multiplier <celery worker --prefetch-multiplier>` option.
  673. Contributed by Mickaël Penhard.
  674. - **Deployment**: Generic init-scripts now support
  675. :envvar:`CELERY_SU`` and :envvar:`CELERYD_SU_ARGS` environment variables
  676. to set the path and arguments for :command:`su` (:manpage:`su(1)`).
  677. - **Prefork**: Prefork pool now uses ``poll`` instead of ``select`` where
  678. available (Issue #2373).
  679. - **Eventlet**: Now returns pool size in :program:`celery inspect stats`
  680. command.
  681. Contributed by Alexander Oblovatniy.
  682. - **Tasks**: New :setting:`email_charset` setting allows for changing
  683. the character set used for outgoing error emails.
  684. Contributed by Vladimir Gorbunov.
  685. - **Worker**: Now respects :setting:`broker_connection_retry` setting.
  686. Fix contributed by Nat Williams.
  687. - **Worker**: Auto-scale did not always update keep-alive when scaling down.
  688. Fix contributed by Philip Garnero.
  689. - **General**: Dates are now always timezone aware even if
  690. :setting:`enable_utc` is disabled (Issue #943).
  691. Fix contributed by Omer Katz.
  692. - **Result Backends**: The redis result backend now has a default socket
  693. timeout of 5 seconds.
  694. The default can be changed using the new :setting:`redis_socket_timeout`
  695. setting.
  696. Contributed by Raghuram Srinivasan.
  697. - **Result Backends**: RPC Backend result queues are now auto delete by
  698. default (Issue #2001).
  699. - **Result Backends**: MongoDB now supports setting the
  700. :setting:`result_serialzier` setting to ``bson`` to use the MongoDB
  701. libraries own serializer.
  702. Contributed by Davide Quarta.
  703. - **Result Backends**: SQLAlchemy result backend now ignores all result
  704. engine options when using NullPool (Issue #1930).
  705. - **Result Backends**: MongoDB URI handling has been improved to use
  706. database name, user and password from the URI if provided.
  707. Contributed by Samuel Jaillet.
  708. - **Result Backends**: Fix problem with RPC/AMQP backends where exception
  709. was not deserialized properly with the json serializer (Issue #2518).
  710. Fix contributed by Allard Hoeve.
  711. - **Result Backends**: Database backend now sets max char size to 155 to deal
  712. with brain damaged MySQL unicode implementation (Issue #1748).
  713. - **General**: All Celery exceptions/warnings now inherit from common
  714. :class:`~celery.exceptions.CeleryException`/:class:`~celery.exceptions.CeleryWarning`.
  715. (Issue #2643).
  716. - **Tasks**: Task retry now also throws in eager mode.
  717. Fix contributed by Feanil Patel.
  718. - **Tasks**: Task error email character set now set to ``utf-8`` by default
  719. (Issue #2737).
  720. - Apps can now define how tasks are named (:meth:`@gen_task_name`).
  721. Contributed by Dmitry Malinovsky
  722. - Module ``celery.worker.job`` renamed to :mod:`celery.worker.request`.
  723. - Beat: ``Scheduler.Publisher``/``.publisher`` renamed to
  724. ``.Producer``/``.producer``.
  725. Incompatible changes
  726. ====================
  727. - Prefork: Calling ``result.get()`` or joining any result from within a task
  728. now raises :exc:`RuntimeError`.
  729. In previous versions this would emit a warning.
  730. - :mod:`celery.worker.consumer` is now a package, not a module.
  731. - Result: The task_name argument/attribute of :class:`@AsyncResult` was
  732. removed.
  733. This was historically a field used for :mod:`pickle` compatibility,
  734. but is no longer needed.
  735. - Backends: Arguments named ``status`` renamed to ``state``.
  736. - Backends: ``backend.get_status()`` renamed to ``backend.get_state()``.
  737. Unscheduled Removals
  738. ====================
  739. - The experimental :mod:`celery.contrib.methods` feature has been removed,
  740. as there were far many bugs in the implementation to be useful.
  741. - The CentOS init-scripts have been removed.
  742. These did not really add any features over the generic init-scripts,
  743. so you are encouraged to use them instead, or something like
  744. :pypi:`supervisor`.
  745. .. _v400-removals:
  746. Scheduled Removals
  747. ==================
  748. Modules
  749. -------
  750. - Module ``celery.worker.job`` has been renamed to :mod:`celery.worker.request`.
  751. This was an internal module so should not have any effect.
  752. It is now part of the public API so should not change again.
  753. - Module ``celery.task.trace`` has been renamed to ``celery.app.trace``
  754. as the ``celery.task`` package is being phased out. The module
  755. will be removed in version 5.0 so please change any import from::
  756. from celery.task.trace import X
  757. to::
  758. from celery.app.trace import X
  759. - Old compatibility aliases in the :mod:`celery.loaders` module
  760. has been removed.
  761. - Removed ``celery.loaders.current_loader()``, use: ``current_app.loader``
  762. - Removed ``celery.loaders.load_settings()``, use: ``current_app.conf``
  763. Result
  764. ------
  765. - ``AsyncResult.serializable()`` and ``celery.result.from_serializable``
  766. has been removed:
  767. Use instead:
  768. .. code-block:: pycon
  769. >>> tup = result.as_tuple()
  770. >>> from celery.result import result_from_tuple
  771. >>> result = result_from_tuple(tup)
  772. - Removed ``BaseAsyncResult``, use ``AsyncResult`` for instance checks
  773. instead.
  774. - Removed ``TaskSetResult``, use ``GroupResult`` instead.
  775. - ``TaskSetResult.total`` -> ``len(GroupResult)``
  776. - ``TaskSetResult.taskset_id`` -> ``GroupResult.id``
  777. - Removed ``ResultSet.subtasks``, use ``ResultSet.results`` instead.
  778. TaskSet
  779. -------
  780. TaskSet has been renamed to group and TaskSet will be removed in version 4.0.
  781. Old::
  782. >>> from celery.task import TaskSet
  783. >>> TaskSet(add.subtask((i, i)) for i in xrange(10)).apply_async()
  784. New::
  785. >>> from celery import group
  786. >>> group(add.s(i, i) for i in xrange(10))()
  787. Events
  788. ------
  789. - Removals for class :class:`celery.events.state.Worker`:
  790. - ``Worker._defaults`` attribute.
  791. Use ``{k: getattr(worker, k) for k in worker._fields}``.
  792. - ``Worker.update_heartbeat``
  793. Use ``Worker.event(None, timestamp, received)``
  794. - ``Worker.on_online``
  795. Use ``Worker.event('online', timestamp, received, fields)``
  796. - ``Worker.on_offline``
  797. Use ``Worker.event('offline', timestamp, received, fields)``
  798. - ``Worker.on_heartbeat``
  799. Use ``Worker.event('heartbeat', timestamp, received, fields)``
  800. - Removals for class :class:`celery.events.state.Task`:
  801. - ``Task._defaults`` attribute.
  802. Use ``{k: getattr(task, k) for k in task._fields}``.
  803. - ``Task.on_sent``
  804. Use ``Worker.event('sent', timestamp, received, fields)``
  805. - ``Task.on_received``
  806. Use ``Task.event('received', timestamp, received, fields)``
  807. - ``Task.on_started``
  808. Use ``Task.event('started', timestamp, received, fields)``
  809. - ``Task.on_failed``
  810. Use ``Task.event('failed', timestamp, received, fields)``
  811. - ``Task.on_retried``
  812. Use ``Task.event('retried', timestamp, received, fields)``
  813. - ``Task.on_succeeded``
  814. Use ``Task.event('succeeded', timestamp, received, fields)``
  815. - ``Task.on_revoked``
  816. Use ``Task.event('revoked', timestamp, received, fields)``
  817. - ``Task.on_unknown_event``
  818. Use ``Task.event(short_type, timestamp, received, fields)``
  819. - ``Task.update``
  820. Use ``Task.event(short_type, timestamp, received, fields)``
  821. - ``Task.merge``
  822. Contact us if you need this.
  823. Magic keyword arguments
  824. -----------------------
  825. Support for the very old magic keyword arguments accepted by tasks is
  826. finally removed in this version.
  827. If you are still using these you have to rewrite any task still
  828. using the old ``celery.decorators`` module and depending
  829. on keyword arguments being passed to the task,
  830. for example::
  831. from celery.decorators import task
  832. @task()
  833. def add(x, y, task_id=None):
  834. print('My task id is %r' % (task_id,))
  835. should be rewritten into::
  836. from celery import task
  837. @task(bind=True)
  838. def add(self, x, y):
  839. print('My task id is {0.request.id}'.format(self))
  840. Settings
  841. --------
  842. The following settings have been removed, and is no longer supported:
  843. Logging Settings
  844. ~~~~~~~~~~~~~~~~
  845. ===================================== =====================================
  846. **Setting name** **Replace with**
  847. ===================================== =====================================
  848. ``CELERYD_LOG_LEVEL`` :option:`celery worker --loglevel`
  849. ``CELERYD_LOG_FILE`` :option:`celery worker --logfile`
  850. ``CELERYBEAT_LOG_LEVEL`` :option:`celery beat --loglevel`
  851. ``CELERYBEAT_LOG_FILE`` :option:`celery beat --loglevel`
  852. ``CELERYMON_LOG_LEVEL`` celerymon is deprecated, use flower.
  853. ``CELERYMON_LOG_FILE`` celerymon is deprecated, use flower.
  854. ``CELERYMON_LOG_FORMAT`` celerymon is deprecated, use flower.
  855. ===================================== =====================================
  856. Task Settings
  857. ~~~~~~~~~~~~~~
  858. ===================================== =====================================
  859. **Setting name** **Replace with**
  860. ===================================== =====================================
  861. ``CELERY_CHORD_PROPAGATES`` N/A
  862. ===================================== =====================================
  863. .. _v400-deprecations:
  864. Deprecation Time-line Changes
  865. =============================
  866. See the :ref:`deprecation-timeline`.
  867. .. _v400-fixes:
  868. Fixes
  869. =====