[docs] More whatsnew-4.0 changes

celery/app/base.py

@@ -90,6 +90,12 @@ def _after_fork_cleanup_app(app):
 
 
 class PendingConfiguration(UserDict, AttributeDictMixin):
+    # `app.conf` will be of this type before being explicitly configured,
+    # which means the app can keep any configuration set directly
+    # on `app.conf` before the `app.config_from_object` call.
+    #
+    # accessing any key will finalize the configuration,
+    # replacing `app.conf` with a concrete settings object.
 
     callback = None
     data = None
@@ -1058,10 +1064,17 @@ class Celery(object):
 
     @property
     def current_worker_task(self):
+        """The task currently being executed by a worker or :const:`None`.
+
+        Differs from :data:`current_task` in that it's not affected
+        by tasks calling other tasks directly, or eagerly.
+
+        """
         return get_current_worker_task()
 
     @cached_property
     def oid(self):
+        """Universally unique identifier for this app."""
         return oid_from(self)
 
     @cached_property

docs/reference/celery.rst

@@ -38,6 +38,8 @@ and creating Celery applications.
 
     .. autoattribute:: current_task
 
+    .. autoattribute:: current_worker_task
+
     .. autoattribute:: amqp
 
     .. autoattribute:: backend
@@ -52,6 +54,8 @@ and creating Celery applications.
     .. autoattribute:: producer_pool
     .. autoattribute:: Task
     .. autoattribute:: timezone
+    .. autoattribute:: builtin_fixups
+    .. autoattribute:: oid
 
     .. automethod:: close
 
@@ -67,6 +71,8 @@ and creating Celery applications.
 
     .. automethod:: add_defaults
 
+    .. automethod:: add_periodic_task
+
     .. automethod:: setup_security
 
     .. automethod:: start
@@ -75,6 +81,8 @@ and creating Celery applications.
 
     .. automethod:: send_task
 
+    .. automethod:: gen_task_name
+
     .. autoattribute:: AsyncResult
 
     .. autoattribute:: GroupResult
@@ -87,6 +95,10 @@ and creating Celery applications.
 
     .. autoattribute:: Beat
 
+    .. automethod:: connection_for_read
+
+    .. automethod:: connection_for_write
+
     .. automethod:: connection
 
     .. automethod:: connection_or_acquire
@@ -101,8 +113,14 @@ and creating Celery applications.
 
     .. automethod:: set_current
 
+    .. automethod:: set_default
+
     .. automethod:: finalize
 
+    .. automethod:: on_init
+
+    .. automethod:: prepare_config
+
     .. data:: on_configure
 
         Signal sent when app is loading configuration.
@@ -115,6 +133,10 @@ and creating Celery applications.
 
         Signal sent after app has been finalized.
 
+    .. data:: on_after_fork
+
+        Signal sent in child process after fork.
+
 Canvas primitives
 -----------------
 
@@ -202,8 +224,8 @@ See :ref:`guide-canvas` for more about creating task workflows.
     arguments will be ignored and the values in the dict will be used
     instead.
 
-        >>> s = signature('tasks.add', args=(2, 2))
-        >>> signature(s)
+        >>> s = app.signature('tasks.add', args=(2, 2))
+        >>> app.signature(s)
         {'task': 'tasks.add', args=(2, 2), kwargs={}, options={}}
 
     .. method:: signature.__call__(*args \*\*kwargs)

docs/userguide/periodic-tasks.rst

@@ -37,14 +37,12 @@ An example time zone could be `Europe/London`:
 
     timezone = 'Europe/London'
 
-
 This setting must be added to your app, either by configuration it directly
 using (``app.conf.timezone = 'Europe/London'``), or by adding
 it to your configuration module if you have set one up using
 ``app.config_from_object``.  See :ref:`celerytut-configuration` for
 more information about configuration options.
 
-
 The default scheduler (storing the schedule in the :file:`celerybeat-schedule`
 file) will automatically detect that the time zone has changed, and so will
 reset the schedule itself, but other schedulers may not be so smart (e.g. the
@@ -103,10 +101,10 @@ beat schedule list.
         print(arg)
 
 
-Setting these up from within the ``on_after_configure`` handler means
+Setting these up from within the :data:`~@on_after_configure` handler means
 that we will not evaluate the app at module level when using ``test.s()``.
 
-The `@add_periodic_task` function will add the entry to the
+The :meth:`~@add_periodic_task` function will add the entry to the
 :setting:`beat_schedule` setting behind the scenes, which also
 can be used to set up periodic tasks manually:
 
@@ -114,15 +112,14 @@ Example: Run the `tasks.add` task every 30 seconds.
 
 .. code-block:: python
 
-    beat_schedule = {
+    app.conf.beat_schedule = {
         'add-every-30-seconds': {
             'task': 'tasks.add',
             'schedule': 30.0,
             'args': (16, 16)
         },
     }
-
-    timezone = 'UTC'
+    app.conf.timezone = 'UTC'
 
 
 .. note::
@@ -131,7 +128,7 @@ Example: Run the `tasks.add` task every 30 seconds.
     please see :ref:`celerytut-configuration`.  You can either
     set these options on your app directly or you can keep
     a separate module for configuration.
-    
+
     If you want to use a single item tuple for `args`, don't forget
     that the constructor is a comma and not a pair of parentheses.
 
@@ -203,7 +200,7 @@ the :class:`~celery.schedules.crontab` schedule type:
 
     from celery.schedules import crontab
 
-    beat_schedule = {
+    app.conf.beat_schedule = {
         # Executes every Monday morning at 7:30 A.M
         'add-every-monday-morning': {
             'task': 'tasks.add',
@@ -285,7 +282,7 @@ sunset, dawn or dusk, you can use the
 
     from celery.schedules import solar
 
-    beat_schedule = {
+    app.conf.beat_schedule = {
         # Executes at sunset in Melbourne
         'add-at-melbourne-sunset': {
             'task': 'tasks.add',

docs/userguide/routing.rst

@@ -87,8 +87,8 @@ configuration:
 
     from kombu import Exchange, Queue
 
-    task_default_queue = 'default'
-    task_queues = (
+    app.conf.task_default_queue = 'default'
+    app.conf.task_queues = (
         Queue('default', Exchange('default'), routing_key='default'),
     )
 
@@ -126,8 +126,8 @@ configuration:
 
     from kombu import Queue
 
-    task_default_queue = 'default'
-    task_queues = (
+    app.conf.task_default_queue = 'default'
+    app.conf.task_queues = (
         Queue('default',    routing_key='task.#'),
         Queue('feed_tasks', routing_key='feed.#'),
     )
@@ -191,7 +191,7 @@ just specify a custom exchange and exchange type:
 
     from kombu import Exchange, Queue
 
-    task_queues = (
+    app.conf.task_queues = (
         Queue('feed_tasks',    routing_key='feed.#'),
         Queue('regular_tasks', routing_key='task.#'),
         Queue('image_tasks',   exchange=Exchange('mediatasks', type='direct'),
@@ -213,6 +213,34 @@ If you're confused about these terms, you should read up on AMQP.
 .. _`Standard Exchange Types`: http://bit.ly/EEWca
 .. _`RabbitMQ FAQ`: http://www.rabbitmq.com/faq.html
 
+.. _routing-special_options:
+
+Special Routing Options
+=======================
+
+.. _routing-option-rabbitmq-priorities:
+
+RabbitMQ Message Priorities
+---------------------------
+:supported transports: rabbitmq
+
+.. versionadded:: 4.0
+
+Queues can be configured to support priorities by setting the
+``x-max-priority`` argument:
+
+.. code-block:: python
+
+    from kombu import Exchange, Queue
+
+    app.conf.task_queues = [
+        Queue('tasks', Exchange('tasks'), routing_key='tasks',
+              queue_arguments={'x-max-priority': 10},
+    ]
+
+A default value for all queues can be set using the
+:setting:`task_queue_max_priority` setting.
+
 .. _amqp-primer:
 
 AMQP Primer
@@ -280,14 +308,14 @@ One for video, one for images and one default queue for everything else:
 
     from kombu import Exchange, Queue
 
-    task_queues = (
+    app.conf.task_queues = (
         Queue('default', Exchange('default'), routing_key='default'),
         Queue('videos',  Exchange('media'),   routing_key='media.video'),
         Queue('images',  Exchange('media'),   routing_key='media.image'),
     )
-    task_default_queue = 'default'
-    task_default_exchange_type = 'direct'
-    task_default_routing_key = 'default'
+    app.conf.task_default_queue = 'default'
+    app.conf.task_default_exchange_type = 'direct'
+    app.conf.task_default_routing_key = 'default'
 
 .. _amqp-exchange-types:
 
@@ -501,14 +529,14 @@ One for video, one for images and one default queue for everything else:
     default_exchange = Exchange('default', type='direct')
     media_exchange = Exchange('media', type='direct')
 
-    task_queues = (
+    app.conf.task_queues = (
         Queue('default', default_exchange, routing_key='default'),
         Queue('videos', media_exchange, routing_key='media.video'),
         Queue('images', media_exchange, routing_key='media.image')
     )
-    task_default_queue = 'default'
-    task_default_exchange = 'default'
-    task_default_routing_key = 'default'
+    app.conf.task_default_queue = 'default'
+    app.conf.task_default_exchange = 'default'
+    app.conf.task_default_routing_key = 'default'
 
 Here, the :setting:`task_default_queue` will be used to route tasks that
 doesn't have an explicit route.
@@ -613,8 +641,8 @@ copies of tasks to all workers connected to it:
 
     from kombu.common import Broadcast
 
-    task_queues = (Broadcast('broadcast_tasks'),)
-    task_routes = {'tasks.reload_cache': {'queue': 'broadcast_tasks'}}
+    app.conf.task_queues = (Broadcast('broadcast_tasks'),)
+    app.conf.task_routes = {'tasks.reload_cache': {'queue': 'broadcast_tasks'}}
 
 Now the ``tasks.reload_cache`` task will be sent to every
 worker consuming from this queue.
@@ -627,9 +655,10 @@ a celerybeat schedule:
     from kombu.common import Broadcast
     from celery.schedules import crontab
 
-    task_queues = (Broadcast('broadcast_tasks'),)
+    app.conf.task_queues = (Broadcast('broadcast_tasks'),)
 
-    beat_schedule = {'test-task': {
+    app.conf.beat_schedule = {
+        'test-task': {
             'task': 'tasks.reload_cache',
             'schedule': crontab(minute=0, hour='*/3'),
             'options': {'exchange': 'broadcast_tasks'}

docs/userguide/tasks.rst

@@ -532,27 +532,21 @@ override this default.
         try:
             …
         except Exception as exc:
-            raise self.retry(exc=exc, countdown=60)  # override the default and
-                                                     # retry in 1 minute
+            # overrides the default delay to retry after 1 minute
+            raise self.retry(exc=exc, countdown=60)
 
-Autoretrying
-------------
+.. _task-autoretry:
 
-.. versionadded:: 4.0
-
-Sometimes you may want to retry a task on particular exception. To do so,
-you should wrap a task body with :keyword:`try` ... :keyword:`except`
-statement, for example:
+Automatic retry for known exceptions
+------------------------------------
 
-.. code-block:: python
+.. versionadded:: 4.0
 
-    @app.task
-    def div(a, b):
-        try:
-            return a / b
-        except ZeroDivisionError as exc:
-            raise div.retry(exc=exc)
+Sometimes you just want to retry a task whenever a particular exception
+is raised.
 
+As this is such a common pattern we have built-in support for it
+with the
 This may not be acceptable all the time, since you may have a lot of such
 tasks.
 
@@ -561,19 +555,34 @@ Fortunately, you can tell Celery to automatically retry a task using
 
 .. code-block:: python
 
-    @app.task(autoretry_for(ZeroDivisionError,))
-    def div(a, b):
-        return a / b
+    from twitter.exceptions import FailWhaleError
+
+    @app.task(autoretry_for=(FailWhaleError,))
+    def refresh_timeline(user):
+        return twitter.refresh_timeline(user)
 
 If you want to specify custom arguments for internal `~@Task.retry`
 call, pass `retry_kwargs` argument to `~@Celery.task` decorator:
 
 .. code-block:: python
 
-    @app.task(autoretry_for=(ZeroDivisionError,),
+    @app.task(autoretry_for=(FailWhaleError,),
               retry_kwargs={'max_retries': 5})
-    def div(a, b):
-        return a / b
+    def refresh_timeline(user):
+        return twitter.refresh_timeline(user)
+
+This is provided as an alternative to manually handling the exceptions,
+and the example above will do the same as wrapping the task body
+in a :keyword:`try` ... :keyword:`except` statement, i.e.:
+
+.. code-block:: python
+
+    @app.task
+    def refresh_timeline(user):
+        try:
+            twitter.refresh_timeline(user)
+        except FailWhaleError as exc:
+            raise div.retry(exc=exc, max_retries=5)
 
 .. _task-options:
 

docs/userguide/workers.rst

@@ -229,8 +229,8 @@ Remote control
     commands from the command-line.  It supports all of the commands
     listed below.  See :ref:`monitoring-control` for more information.
 
-pool support: *prefork, eventlet, gevent*, blocking:*threads/solo* (see note)
-broker support: *amqp, redis*
+:pool support: *prefork, eventlet, gevent*, blocking:*threads/solo* (see note)
+:broker support: *amqp, redis*
 
 Workers have the ability to be remote controlled using a high-priority
 broadcast message queue.  The commands can be directed to all, or a specific
@@ -419,7 +419,7 @@ Time Limits
 
 .. versionadded:: 2.0
 
-pool support: *prefork/gevent*
+:pool support: *prefork/gevent*
 
 .. sidebar:: Soft, or hard?
 
@@ -464,7 +464,7 @@ Changing time limits at runtime
 -------------------------------
 .. versionadded:: 2.3
 
-broker support: *amqp, redis*
+:broker support: *amqp, redis*
 
 There is a remote control command that enables you to change both soft
 and hard time limits for a task — named ``time_limit``.
@@ -519,7 +519,7 @@ Max tasks per child setting
 
 .. versionadded:: 2.0
 
-pool support: *prefork*
+:pool support: *prefork*
 
 With this option you can configure the maximum number of tasks
 a worker can execute before it's replaced by a new process.
@@ -527,15 +527,17 @@ a worker can execute before it's replaced by a new process.
 This is useful if you have memory leaks you have no control over
 for example from closed source C extensions.
 
-The option can be set using the workers `--maxtasksperchild` argument
+The option can be set using the workers :option:`--maxtasksperchild` argument
 or using the :setting:`worker_max_tasks_per_child` setting.
 
+.. _worker-maxmemperchild:
+
 Max memory per child setting
 ============================
 
-.. versionadded:: TODO
+.. versionadded:: 4.0
 
-pool support: *prefork*
+:pool support: *prefork*
 
 With this option you can configure the maximum amount of resident
 memory a worker can execute before it's replaced by a new process.
@@ -543,8 +545,8 @@ memory a worker can execute before it's replaced by a new process.
 This is useful if you have memory leaks you have no control over
 for example from closed source C extensions.
 
-The option can be set using the workers `--maxmemperchild` argument
-or using the :setting:`CELERYD_MAX_MEMORY_PER_CHILD` setting.
+The option can be set using the workers :option:`--maxmemperchild` argument
+or using the :setting:`worker_max_memory_per_child` setting.
 
 .. _worker-autoscaling:
 
@@ -553,7 +555,7 @@ Autoscaling
 
 .. versionadded:: 2.2
 
-pool support: *prefork*, *gevent*
+:pool support: *prefork*, *gevent*
 
 The *autoscaler* component is used to dynamically resize the pool
 based on load:
@@ -728,7 +730,7 @@ Autoreloading
 
 .. versionadded:: 2.5
 
-pool support: *prefork, eventlet, gevent, threads, solo*
+:pool support: *prefork, eventlet, gevent, threads, solo*
 
 Starting :program:`celery worker` with the :option:`--autoreload` option will
 enable the worker to watch for file system changes to all imported task

docs/whatsnew-4.0.rst

@@ -45,6 +45,44 @@ Preface
 =======
 
 
+Wall of Contributors
+--------------------
+
+Aaron McMillin, Adam Renberg, Adrien Guinet, Ahmet Demir, Aitor Gómez-Goiri,
+Albert Wang, Alex Koshelev, Alex Rattray, Alex Williams, Alexander Koshelev,
+Alexander Lebedev, Alexander Oblovatniy, Alexey Kotlyarov, Ali Bozorgkhan,
+Alice Zoë Bevan–McGregor, Allard Hoeve, Alman One, Andrea Rabbaglietti,
+Andrea Rosa, Andrei Fokau, Andrew Rodionoff, Andriy Yurchuk,
+Aneil Mallavarapu, Areski Belaid, Artyom Koval, Ask Solem, Balthazar Rouberol,
+Berker Peksag, Bert Vanderbauwhede, Brian Bouterse, Chris Duryee, Chris Erway,
+Chris Harris, Chris Martin, Corey Farwell, Craig Jellick, Cullen Rhodes,
+Dallas Marlow, Daniel Wallace, Danilo Bargen, Davanum Srinivas, Dave Smith,
+David Baumgold, David Harrigan, David Pravec, Dennis Brakhane, Derek Anderson,
+Dmitry Malinovsky, Dudás Ádám, Dustin J. Mitchell, Ed Morley, Fatih Sucu,
+Feanil Patel, Felix Schwarz, Fernando Rocha, Flavio Grossi, Frantisek Holop,
+Gao Jiangmiao, Gerald Manipon, Gilles Dartiguelongue, Gino Ledesma,
+Hank John, Hogni Gylfason, Ilya Georgievsky, Ionel Cristian Mărieș,
+James Pulec, Jared Lewis, Jason Veatch, Jasper Bryant-Greene, Jeremy Tillman,
+Jocelyn Delalande, Joe Jevnik, John Anderson, John Kirkham, John Whitlock,
+Joshua Harlow, Juan Rossi, Justin Patrin, Kai Groner, Kevin Harvey,
+Konstantinos Koukopoulos, Kouhei Maeda, Kracekumar Ramaraju,
+Krzysztof Bujniewicz, Latitia M. Haskins, Len Buckens, Lorenzo Mancini,
+Lucas Wiman, Luke Pomfrey, Marcio Ribeiro, Marin Atanasov Nikolov,
+Mark Parncutt, Maxime Vdb, Mher Movsisyan, Michael (michael-k),
+Michael Duane Mooring, Michael Permana, Mickaël Penhard, Mike Attwood,
+Morton Fox, Môshe van der Sterre, Nat Williams, Nathan Van Gheem, Nik Nyby,
+Omer Katz, Omer Korner, Ori Hoch, Paul Pearce, Paulo Bu, Philip Garnero,
+Piotr Maślanka, Radek Czajka, Raghuram Srinivasan, Randy Barlow,
+Rodolfo Carvalho, Roger Hu, Rongze Zhu, Ross Deane, Ryan Luckie,
+Rémy Greinhofer, Samuel Jaillet, Sergey Azovskov, Sergey Tikhonov,
+Seungha Kim, Steve Peak, Sukrit Khera, Tadej Janež, Tewfik Sadaoui,
+Thomas French, Thomas Grainger, Tobias Schottdorf, Tocho Tochev,
+Valentyn Klindukh, Vic Kumar, Vladimir Bolshakov, Vladimir Gorbunov,
+Wayne Chang, Wil Langford, Will Thompson, William King, Yury Selivanov,
+Zoran Pavlovic, 許邱翔, @allenling, @bee-keeper, @ffeast, @flyingfoxlee,
+@gdw2, @gitaarik, @hankjin, @m-vdb, @mdk, @nokrik, @ocean1, @orlo666,
+@raducc, @wanglei, @worldexception.
+
 .. _v400-important:
 
 Important Notes
@@ -278,6 +316,31 @@ and the Django handler will automatically find your installed apps:
 The Django integration :ref:`example in the documentation
 <django-first-steps>` has been updated to use the argument-less call.
 
+Worker direct queues no longer use auto-delete.
+===============================================
+
+Workers/clients running 4.0 will no longer be able to send
+worker direct messages to worker running older versions, and vice versa.
+
+If you're relying on worker direct messages you should upgrade
+your 3.x workers and clients to use the new routing settings first,
+by replacing :func:`celery.utils.worker_direct` with this implementation:
+
+.. code-block:: python
+
+    from kombu import Exchange, Queue
+
+    worker_direct_exchange = Exchange('C.dq2')
+
+    def worker_direct(hostname):
+        return Queue(
+            '{hostname}.dq2'.format(hostname),
+            exchange=worker_direct_exchange,
+            routing_key=hostname,
+        )
+
+(This feature closed Issue #2492.)
+
 
 Old command-line programs removed
 ---------------------------------
@@ -441,8 +504,8 @@ log file can cause corruption.
 You are encouraged to upgrade your init scripts and multi arguments
 to use this new option.
 
-Ability to configure separate broker urls for read/write
-========================================================
+Configure broker URL for read/write separately.
+===============================================
 
 New :setting:`broker_read_url` and :setting:`broker_write_url` settings
 have been added so that separate broker urls can be provided
@@ -476,6 +539,9 @@ the intent of the required connection.
 Canvas Refactor
 ===============
 
+The canvas/workflow implementation have been heavily refactored
+to fix some long outstanding issues.
+
 # BLALBLABLA
 d79dcd8e82c5e41f39abd07ffed81ca58052bcd2
 1e9dd26592eb2b93f1cb16deb771cfc65ab79612
@@ -485,7 +551,7 @@ e442df61b2ff1fe855881c1e2ff9acc970090f54
 - Now unrolls groups within groups into a single group (Issue #1509).
 - chunks/map/starmap tasks now routes based on the target task
 - chords and chains can now be immutable.
-- Fixed bug where serialized signature were not converted back into
+- Fixed bug where serialized signatures were not converted back into
   signatures (Issue #2078)
 
     Fix contributed by Ross Deane.
@@ -521,8 +587,13 @@ See :ref:`beat-solar` for more information.
 
 Contributed by Mark Parncutt.
 
-App can now configure periodic tasks
-====================================
+New API for configuring periodic tasks
+======================================
+
+This new API enables you to use signatures when defining periodic tasks,
+removing the chance of mistyping task names.
+
+An example of the new API is :ref:`here <beat-entries>`.
 
 # bc18d0859c1570f5eb59f5a969d1d32c63af764b
 # 132d8d94d38f4050db876f56a841d5a5e487b25b
@@ -530,84 +601,119 @@ App can now configure periodic tasks
 RabbitMQ Priority queue support
 ===============================
 
-# 1d4cbbcc921aa34975bde4b503b8df9c2f1816e0
+See :ref:`routing-options-rabbitmq-priorities` for more information.
 
 Contributed by Gerald Manipon.
 
-Incompatible: Worker direct queues are no longer using auto-delete.
-===================================================================
+Prefork: Limit child process resident memory size.
+==================================================
+# 5cae0e754128750a893524dcba4ae030c414de33
 
-Issue #2492.
+You can now limit the maximum amount of memory allocated per prefork
+pool child process by setting the worker :option:`--maxmemperchild` option,
+or the :setting:`worker_max_memory_per_child` setting.
 
-Prefork: Limits for child process resident memory size.
-=======================================================
+The limit is for RSS/resident memory size and is specified in kilobytes.
 
-This version introduces the new :setting:`worker_max_memory_per_child` setting,
-which BLA BLA BLA
+A child process having exceeded the limit will be terminated and replaced
+with a new process after the currently executing task returns.
 
-# 5cae0e754128750a893524dcba4ae030c414de33
+See :ref:`worker-maxmemperchild` for more information.
 
 Contributed by Dave Smith.
 
 Redis: Result backend optimizations
 ===============================================
 
-Pub/sub results
----------------
+RPC is now using pub/sub for streaming task results.
+----------------------------------------------------
+
+Calling ``result.get()`` when using the Redis result backend
+used to be extremely expensive as it was using polling to wait
+for the result to become available. A default polling
+interval of 0.5 seconds did not help performance, but was
+necessary to avoid a spin loop.
+
+The new implementation is using Redis Pub/Sub mechanisms to
+publish and retrieve results immediately, greatly improving
+task round-trip times.
 
 Contributed by Yaroslav Zhavoronkov and Ask Solem.
 
-Chord join
-----------
+New optimized chord join implementation.
+----------------------------------------
 
 This was an experimental feature introduced in Celery 3.1,
-but is now enabled by default.
+that could only be enabled by adding ``?new_join=1`` to the
+result backend URL configuration.
 
-?new_join BLABLABLA
+We feel that the implementation has been tested thoroughly enough
+to be considered stable and enabled by default.
 
-Riak Result Backend
-===================
+The new implementation greatly reduces the overhead of chords,
+and especially with larger chords the performance benefit can be massive.
 
-Contributed by Gilles Dartiguelongue, Alman One and NoKriK.
+New Riak result backend Introduced.
+===================================
 
-Bla bla
+See :ref:`conf-riak-result-backend` for more information.
 
-- blah blah
+Contributed by Gilles Dartiguelongue, Alman One and NoKriK.
+
+New CouchDB result backend introduced.
+======================================
 
-CouchDB Result Backend
-======================
+See :ref:`conf-couchdb-result-backend` for more information.
 
 Contributed by Nathan Van Gheem
 
-New Cassandra Backend
-=====================
+Brand new Cassandra result backend.
+===================================
 
-The new Cassandra backend utilizes the python-driver library.
-Old backend is deprecated and everyone using cassandra is required to upgrade
-to be using the new driver.
+A brand new Cassandra backend utilizing the new :pypi:`cassandra-driver`
+library is replacing the old result backend which was using the older
+:pypi:`pycassa` library.
+
+See :ref:`conf-cassandra-result-backend` for more information.
 
 # XXX What changed?
 
+New Elasticsearch result backend introduced.
+============================================
 
-Elasticsearch Result Backend
-============================
+See :ref:`conf-elasticsearch-result-backend` for more information.
 
 Contributed by Ahmet Demir.
 
-Filesystem Result Backend
-=========================
+New Filesystem result backend introduced.
+=========================================
+
+See :ref:`conf-filesystem-result-backend` for more information.
 
 Contributed by Môshe van der Sterre.
 
 Event Batching
 ==============
 
-Events are now buffered in the worker and sent as a list, and
-events are sent as transient messages by default so that they are not written
-to disk by RabbitMQ.
+Events are now buffered in the worker and sent as a list which reduces
+the overhead required to send monitoring events.
 
-03399b4d7c26fb593e61acf34f111b66b340ba4e
+For authors of custom event monitors there will be no action
+required as long as you're using the Python celery
+helpers (:class:`~@events.Receiver`) to implement your monitor.
+However, if you're manually receiving event messages you must now account
+for batched event messages which differ from normal event messages
+in the following way:
+
+    - The routing key for a batch of event messages will be set to
+      ``<event-group>.multi`` where the only batched event group
+      is currently ``task`` (giving a routing key of ``task.multi``).
 
+    - The message body will be a serialized list-of-dictionaries instead
+      of a dictionary.  Each item in the list can be regarded
+      as a normal event message body.
+
+03399b4d7c26fb593e61acf34f111b66b340ba4e
 
 Task.replace
 ============
@@ -636,19 +742,26 @@ Closes #817
 Optimized Beat implementation
 =============================
 
-heapq
-20340d79b55137643d5ac0df063614075385daaa
+The :program:`celery beat` implementation has been optimized
+for millions of periodic tasks by using a heap to schedule entries.
 
 Contributed by Ask Solem and Alexander Koshelev.
 
-
 Task Autoretry Decorator
 ========================
 
-75246714dd11e6c463b9dc67f4311690643bff24
+Writing custom retry handling for exception events is so common
+that we now have built-in support for it.
+
+For this a new ``autoretry_for`` argument is now supported by
+the task decorators, where you can specify a tuple of exceptions
+to automatically retry for.
+
+See :ref:`task-autoretry` for more information.
 
 Contributed by Dmitry Malinovsky.
 
+# 75246714dd11e6c463b9dc67f4311690643bff24
 
 Async Result API
 ================
@@ -657,12 +770,6 @@ eventlet/gevent drainers, promises, BLA BLA
 
 Closed issue #2529.
 
-
-:setting:`task_routes` can now contain glob patterns and regexes.
-=================================================================
-
-See examples in :setting:`task_routes` and :ref:`routing-automatic`.
-
 In Other News
 -------------
 
@@ -680,6 +787,11 @@ In Other News
   This increases performance as it completely bypasses the routing table,
   in addition it also improves reliability for the Redis broker transport.
 
+- **Tasks**: :setting:`task_routes` can now contain glob patterns and
+  regexes.
+
+    See new examples in :setting:`task_routes` and :ref:`routing-automatic`.
+
 - **Eventlet/Gevent**: Fixed race condition leading to "simultaneous read"
   errors (Issue #2812).