# Change history {#changelog-4.3}

This document contains change notes for bugfix releases in the 4.3.x
series, please see `whatsnew-4.3`{.interpreted-text role="ref"} for an
overview of what\'s new in Celery 4.3.

## 4.3.1

release-date

:   2020-09-10 1:00 P.M UTC+3:00

release-by

:   Omer Katz

-   Limit vine version to be below 5.0.0.

    Contributed by **Omer Katz**

## 4.3.0

release-date

:   2019-03-31 7:00 P.M UTC+3:00

release-by

:   Omer Katz

-   Added support for broadcasting using a regular expression pattern or
    a glob pattern to multiple Pidboxes.

    This allows you to inspect or ping multiple workers at once.

    Contributed by **Dmitry Malinovsky** & **Jason Held**

-   Added support for PEP 420 namespace packages.

    This allows you to load tasks from namespace packages.

    Contributed by **Colin Watson**

-   Added `acks_on_failure_or_timeout`{.interpreted-text role="setting"}
    as a setting instead of a task only option.

    This was missing from the original PR but now added for
    completeness.

    Contributed by **Omer Katz**

-   Added the `task_received`{.interpreted-text role="signal"} signal.

    Contributed by **Omer Katz**

-   Fixed a crash of our CLI that occurred for everyone using Python \<
    3.6.

    The crash was introduced in
    [acd6025](https://github.com/celery/celery/commit/acd6025b7dc4db112a31020686fc8b15e1722c67)
    by using the `ModuleNotFoundError`{.interpreted-text role="class"}
    exception which was introduced in Python 3.6.

    Contributed by **Omer Katz**

-   Fixed a crash that occurred when using the Redis result backend
    while the `result_expires`{.interpreted-text role="setting"} is set
    to None.

    Contributed by **Toni Ruža** & **Omer Katz**

-   Added support the [DNS seedlist connection
    format](https://docs.mongodb.com/manual/reference/connection-string/#dns-seedlist-connection-format)
    for the MongoDB result backend.

    This requires the [dnspython]{.title-ref} package which will be
    installed by default when installing the dependencies for the
    MongoDB result backend.

    Contributed by **George Psarakis**

-   Bump the minimum eventlet version to 0.24.1.

    Contributed by **George Psarakis**

-   Replace the [msgpack-python]{.title-ref} package with
    [msgpack]{.title-ref}.

    We\'re no longer using the deprecated package. See our
    `important notes <v430-important>`{.interpreted-text role="ref"} for
    this release for further details on how to upgrade.

    Contributed by **Daniel Hahler**

-   Allow scheduling error handlers which are not registered tasks in
    the current worker.

    These kind of error handlers are now possible:

    ``` python
    from celery import Signature
    Signature(
      'bar', args=['foo'],
      link_error=Signature('msg.err', queue='msg')
    ).apply_async()
    ```

-   Additional fixes and enhancements to the SSL support of the Redis
    broker and result backend.

    Contributed by **Jeremy Cohen**

Code Cleanups, Test Coverage & CI Improvements by:

> -   **Omer Katz**
> -   **Florian Chardin**

Documentation Fixes by:

> -   **Omer Katz**
> -   **Samuel Huang**
> -   **Amir Hossein Saeid Mehr**
> -   **Dmytro Litvinov**

## 4.3.0 RC2

release-date

:   2019-03-03 9:30 P.M UTC+2:00

release-by

:   Omer Katz

-   **Filesystem Backend**: Added meaningful error messages for
    filesystem backend.

    Contributed by **Lars Rinn**

-   **New Result Backend**: Added the ArangoDB backend.

    Contributed by **Dilip Vamsi Moturi**

-   **Django**: Prepend current working directory instead of appending
    so that the project directory will have precedence over system
    modules as expected.

    Contributed by **Antonin Delpeuch**

-   Bump minimum py-redis version to 3.2.0.

    Due to multiple bugs in earlier versions of py-redis that were
    causing issues for Celery, we were forced to bump the minimum
    required version to 3.2.0.

    Contributed by **Omer Katz**

-   **Dependencies**: Bump minimum required version of Kombu to 4.4

    Contributed by **Omer Katz**

## 4.3.0 RC1

release-date

:   2019-02-20 5:00 PM IST

release-by

:   Omer Katz

-   **Canvas**: `celery.chain.apply`{.interpreted-text role="meth"} does
    not ignore keyword arguments anymore when applying the chain.

    Contributed by **Korijn van Golen**

-   **Result Set**: Don\'t attempt to cache results in a
    `celery.result.ResultSet`{.interpreted-text role="class"}.

    During a join, the results cache was populated using
    `celery.result.ResultSet.get`{.interpreted-text role="meth"}, if one
    of the results contains an exception, joining unexpectedly failed.

    The results cache is now removed.

    Contributed by **Derek Harland**

-   **Application**:
    `celery.Celery.autodiscover_tasks`{.interpreted-text role="meth"}
    now attempts to import the package itself when the
    [related_name]{.title-ref} keyword argument is [None]{.title-ref}.

    Contributed by **Alex Ioannidis**

-   **Windows Support**: On Windows 10, stale PID files prevented celery
    beat to run. We now remove them when a
    `SystemExit`{.interpreted-text role="class"} is raised.

    Contributed by **:github_user:\`na387\`**

-   **Task**: Added the new
    `task_acks_on_failure_or_timeout`{.interpreted-text role="setting"}
    setting.

    Acknowledging SQS messages on failure or timing out makes it
    impossible to use dead letter queues.

    We introduce the new option acks_on_failure_or_timeout, to ensure we
    can totally fallback on native SQS message lifecycle, using
    redeliveries for retries (in case of slow processing or failure) and
    transitions to dead letter queue after defined number of times.

    Contributed by **Mario Kostelac**

-   **RabbitMQ Broker**: Adjust HA headers to work on RabbitMQ 3.x.

    This change also means we\'re ending official support for RabbitMQ
    2.x.

    Contributed by **Asif Saif Uddin**

-   **Command Line**: Improve `celery update`{.interpreted-text
    role="program"} error handling.

    Contributed by **Federico Bond**

-   **Canvas**: Support chords with
    `task_always_eager`{.interpreted-text role="setting"} set to
    [True]{.title-ref}.

    Contributed by **Axel Haustant**

-   **Result Backend**: Optionally store task properties in result
    backend.

    Setting the `result_extended`{.interpreted-text role="setting"}
    configuration option to [True]{.title-ref} enables storing
    additional task properties in the result backend.

    Contributed by **John Arnold**

-   **Couchbase Result Backend**: Allow the Couchbase result backend to
    automatically detect the serialization format.

    Contributed by **Douglas Rohde**

-   **New Result Backend**: Added the Azure Block Blob Storage result
    backend.

    The backend is implemented on top of the azure-storage library which
    uses Azure Blob Storage for a scalable low-cost PaaS backend.

    The backend was load tested via a simple nginx/gunicorn/sanic app
    hosted on a DS4 virtual machine (4 vCores, 16 GB RAM) and was able
    to handle 600+ concurrent users at \~170 RPS.

    The commit also contains a live end-to-end test to facilitate
    verification of the backend functionality. The test is activated by
    setting the [AZUREBLOCKBLOB_URL]{.title-ref} environment variable to
    [azureblockblob://{ConnectionString}]{.title-ref} where the value
    for [ConnectionString]{.title-ref} can be found in the [Access
    Keys]{.title-ref} pane of a Storage Account resources in the Azure
    Portal.

    Contributed by **Clemens Wolff**

-   **Task**: `celery.app.task.update_state`{.interpreted-text
    role="meth"} now accepts keyword arguments.

    This allows passing extra fields to the result backend. These fields
    are unused by default but custom result backends can use them to
    determine how to store results.

    Contributed by **Christopher Dignam**

-   Gracefully handle consumer
    `kombu.exceptions.DecodeError`{.interpreted-text role="class"}.

    When using the v2 protocol the worker no longer crashes when the
    consumer encounters an error while decoding a message.

    Contributed by **Steven Sklar**

-   **Deployment**: Fix init.d service stop.

    Contributed by **Marcus McHale**

-   **Django**: Drop support for Django \< 1.11.

    Contributed by **Asif Saif Uddin**

-   **Django**: Remove old djcelery loader.

    Contributed by **Asif Saif Uddin**

-   **Result Backend**:
    `celery.worker.request.Request`{.interpreted-text role="class"} now
    passes `celery.app.task.Context`{.interpreted-text role="class"} to
    the backend\'s store_result functions.

    Since the class currently passes [self]{.title-ref} to these
    functions, revoking a task resulted in corrupted task result data
    when django-celery-results was used.

    Contributed by **Kiyohiro Yamaguchi**

-   **Worker**: Retry if the heartbeat connection dies.

    Previously, we keep trying to write to the broken connection. This
    results in a memory leak because the event dispatcher will keep
    appending the message to the outbound buffer.

    Contributed by **Raf Geens**

-   **Celery Beat**: Handle microseconds when scheduling.

    Contributed by **K Davis**

-   **Asynpool**: Fixed deadlock when closing socket.

    Upon attempting to close a socket,
    `celery.concurrency.asynpool.AsynPool`{.interpreted-text
    role="class"} only removed the queue writer from the hub but did not
    remove the reader. This led to a deadlock on the file descriptor and
    eventually the worker stopped accepting new tasks.

    We now close both the reader and the writer file descriptors in a
    single loop iteration which prevents the deadlock.

    Contributed by **Joshua Engelman**

-   **Celery Beat**: Correctly consider timezone when calculating
    timestamp.

    Contributed by **:github_user:\`yywing\`**

-   **Celery Beat**:
    `celery.beat.Scheduler.schedules_equal`{.interpreted-text
    role="meth"} can now handle either arguments being a
    [None]{.title-ref} value.

    Contributed by **:github_user:\` ratson\`**

-   **Documentation/Sphinx**: Fixed Sphinx support for shared_task
    decorated functions.

    Contributed by **Jon Banafato**

-   **New Result Backend**: Added the CosmosDB result backend.

    This change adds a new results backend. The backend is implemented
    on top of the pydocumentdb library which uses Azure CosmosDB for a
    scalable, globally replicated, high-performance, low-latency and
    high-throughput PaaS backend.

    Contributed by **Clemens Wolff**

-   **Application**: Added configuration options to allow separate
    multiple apps to run on a single RabbitMQ vhost.

    The newly added `event_exchange`{.interpreted-text role="setting"}
    and `control_exchange`{.interpreted-text role="setting"}
    configuration options allow users to use separate Pidbox exchange
    and a separate events exchange.

    This allow different Celery applications to run separately on the
    same vhost.

    Contributed by **Artem Vasilyev**

-   **Result Backend**: Forget parent result metadata when forgetting a
    result.

    Contributed by **:github_user:\`tothegump\`**

-   **Task** Store task arguments inside
    `celery.exceptions.MaxRetriesExceededError`{.interpreted-text
    role="class"}.

    Contributed by **Anthony Ruhier**

-   **Result Backend**: Added the
    `result_accept_content`{.interpreted-text role="setting"} setting.

    This feature allows to configure different accepted content for the
    result backend.

    A special serializer ([auth]{.title-ref}) is used for signed
    messaging, however the result_serializer remains in json, because we
    don\'t want encrypted content in our result backend.

    To accept unsigned content from the result backend, we introduced
    this new configuration option to specify the accepted content from
    the backend.

-   **Canvas**: Fixed error callback processing for class based tasks.

    Contributed by **Victor Mireyev**

-   **New Result Backend**: Added the S3 result backend.

    Contributed by **Florian Chardin**

-   **Task**: Added support for Cythonized Celery tasks.

    Contributed by **Andrey Skabelin**

-   **Riak Result Backend**: Warn Riak backend users for possible Python
    3.7 incompatibilities.

    Contributed by **George Psarakis**

-   **Python Runtime**: Added Python 3.7 support.

    Contributed by **Omer Katz** & **Asif Saif Uddin**

-   **Auth Serializer**: Revamped the auth serializer.

    The auth serializer received a complete overhaul. It was previously
    horribly broken.

    We now depend on cryptography instead of pyOpenSSL for this
    serializer.

-   **Command Line**: `celery report`{.interpreted-text role="program"}
    now reports kernel version along with other platform details.

    Contributed by **Omer Katz**

-   **Canvas**: Fixed chords with chains which include sub chords in a
    group.

    Celery now correctly executes the last task in these types of
    canvases:

    ``` python
    c = chord(
      group([
          chain(
              dummy.si(),
              chord(
                  group([dummy.si(), dummy.si()]),
                  dummy.si(),
              ),
          ),
          chain(
              dummy.si(),
              chord(
                  group([dummy.si(), dummy.si()]),
                  dummy.si(),
              ),
          ),
      ]),
      dummy.si()
    )

    c.delay().get()
    ```

    Contributed by **Maximilien Cuony**

-   **Canvas**: Complex canvases with error callbacks no longer raises
    an `AttributeError`{.interpreted-text role="class"}.

    Very complex canvases such as
    [this](https://github.com/merchise/xopgi.base/blob/6634819ad5c701c04bc9baa5c527449070843b71/xopgi/xopgi_cdr/cdr_agent.py#L181)
    no longer raise an `AttributeError`{.interpreted-text role="class"}
    which prevents constructing them.

    We do not know why this bug occurs yet.

    Contributed by **Manuel Vázquez Acosta**

-   **Command Line**: Added proper error messages in cases where app
    cannot be loaded.

    Previously, celery crashed with an exception.

    We now print a proper error message.

    Contributed by **Omer Katz**

-   **Task**: Added the `task_default_priority`{.interpreted-text
    role="setting"} setting.

    You can now set the default priority of a task using the
    `task_default_priority`{.interpreted-text role="setting"} setting.
    The setting\'s value will be used if no priority is provided for a
    specific task.

    Contributed by **:github_user:\`madprogrammer\`**

-   **Dependencies**: Bump minimum required version of Kombu to 4.3 and
    Billiard to 3.6.

    Contributed by **Asif Saif Uddin**

-   **Result Backend**: Fix memory leak.

    We reintroduced weak references to bound methods for AsyncResult
    callback promises, after adding full weakref support for Python 2 in
    [vine](https://github.com/celery/vine/tree/v1.2.0). More details can
    be found in
    [celery/celery#4839](https://github.com/celery/celery/pull/4839).

    Contributed by **George Psarakis** and
    **:github_user:\`monsterxx03\`**.

-   **Task Execution**: Fixed roundtrip serialization for eager tasks.

    When doing the roundtrip serialization for eager tasks, the task
    serializer will always be JSON unless the [serializer]{.title-ref}
    argument is present in the call to
    `celery.app.task.Task.apply_async`{.interpreted-text role="meth"}.
    If the serializer argument is present but is
    [\'pickle\']{.title-ref}, an exception will be raised as
    pickle-serialized objects cannot be deserialized without specifying
    to [serialization.loads]{.title-ref} what content types should be
    accepted. The Producer\'s [serializer]{.title-ref} seems to be set
    to [None]{.title-ref}, causing the default to JSON serialization.

    We now continue to use (in order) the [serializer]{.title-ref}
    argument to `celery.app.task.Task.apply_async`{.interpreted-text
    role="meth"}, if present, or the [Producer]{.title-ref}\'s
    serializer if not [None]{.title-ref}. If the
    [Producer]{.title-ref}\'s serializer is [None]{.title-ref}, it will
    use the Celery app\'s [task_serializer]{.title-ref} configuration
    entry as the serializer.

    Contributed by **Brett Jackson**

-   **Redis Result Backend**: The
    `celery.backends.redis.ResultConsumer`{.interpreted-text
    role="class"} class no longer assumes
    `celery.backends.redis.ResultConsumer.start`{.interpreted-text
    role="meth"} to be called before
    `celery.backends.redis.ResultConsumer.drain_events`{.interpreted-text
    role="meth"}.

    This fixes a race condition when using the Gevent workers pool.

    Contributed by **Noam Kush**

-   **Task**: Added the `task_inherit_parent_priority`{.interpreted-text
    role="setting"} setting.

    Setting the `task_inherit_parent_priority`{.interpreted-text
    role="setting"} configuration option to [True]{.title-ref} will make
    Celery tasks inherit the priority of the previous task linked to it.

    Examples:

    ``` python
    c = celery.chain(
      add.s(2), # priority=None
      add.s(3).set(priority=5), # priority=5
      add.s(4), # priority=5
      add.s(5).set(priority=3), # priority=3
      add.s(6), # priority=3
    )
    ```

    ``` python
    @app.task(bind=True)
    def child_task(self):
      pass

    @app.task(bind=True)
    def parent_task(self):
      child_task.delay()

    # child_task will also have priority=5
    parent_task.apply_async(args=[], priority=5)
    ```

    Contributed by **:github_user:\`madprogrammer\`**

-   **Canvas**: Added the `result_chord_join_timeout`{.interpreted-text
    role="setting"} setting.

    Previously, `celery.result.GroupResult.join`{.interpreted-text
    role="meth"} had a fixed timeout of 3 seconds.

    The `result_chord_join_timeout`{.interpreted-text role="setting"}
    setting now allows you to change it.

    Contributed by **:github_user:\`srafehi\`**

Code Cleanups, Test Coverage & CI Improvements by:

> -   **Jon Dufresne**
> -   **Asif Saif Uddin**
> -   **Omer Katz**
> -   **Brett Jackson**
> -   **Bruno Alla**
> -   **:github_user:\`tothegump\`**
> -   **Bojan Jovanovic**
> -   **Florian Chardin**
> -   **:github_user:\`walterqian\`**
> -   **Fabian Becker**
> -   **Lars Rinn**
> -   **:github_user:\`madprogrammer\`**
> -   **Ciaran Courtney**

Documentation Fixes by:

> -   **Lewis M. Kabui**
> -   **Dash Winterson**
> -   **Shanavas M**
> -   **Brett Randall**
> -   **Przemysław Suliga**
> -   **Joshua Schmid**
> -   **Asif Saif Uddin**
> -   **Xiaodong**
> -   **Vikas Prasad**
> -   **Jamie Alessio**
> -   **Lars Kruse**
> -   **Guilherme Caminha**
> -   **Andrea Rabbaglietti**
> -   **Itay Bittan**
> -   **Noah Hall**
> -   **Peng Weikang**
> -   **Mariatta Wijaya**
> -   **Ed Morley**
> -   **Paweł Adamczak**
> -   **:github_user:\`CoffeeExpress\`**
> -   **:github_user:\`aviadatsnyk\`**
> -   **Brian Schrader**
> -   **Josue Balandrano Coronel**
> -   **Tom Clancy**
> -   **Sebastian Wojciechowski**
> -   **Meysam Azad**
> -   **Willem Thiart**
> -   **Charles Chan**
> -   **Omer Katz**
> -   **Milind Shakya**