This document describes the current stable version of Celery (5.6). For development docs, go here.

# Change history

This document contains change notes for bugfix releases in the 4.2.x series, please see What’s new in Celery 4.2 (windowlicker) for an overview of what’s new in Celery 4.2.

## 4.2.1

release-date:

  2018-07-18 11:00 AM IST

release-by:

  Omer Katz

- Result Backend: Fix deserialization of exceptions that are present in the producer codebase but not in the consumer codebase.

  Contributed by John Arnold

- Message Protocol Compatibility: Fix error caused by an invalid (None) timelimit value in the message headers when migrating messages from 3.x to 4.x.

  Contributed by Robert Kopaczewski

- Result Backend: Fix serialization of exception arguments when exception arguments are not JSON serializable by default.

  Contributed by Tom Booth

- Worker: Fixed multiple issues with rate limited tasks

  Maintain scheduling order. Fix possible scheduling of a `celery.worker.request.Request` with the wrong `kombu.utils.limits.TokenBucket` which could cause tasks’ rate limit to behave incorrectly. Fix possible duplicated execution of tasks that were rate limited or if ETA/Countdown was provided for them.

  Contributed by @ideascf

- Worker: Defensively handle invalid timelimit header values in requests.

  Contributed by Omer Katz

Documentation fixes:

> - Matt Wiens

> - Seunghun Lee

> - Lewis M. Kabui

> - Prathamesh Salunkhe

## 4.2.0

release-date:

  2018-06-10 21:30 PM IST

release-by:

  Omer Katz

- Task: Add `ignore_result` as task execution option (#4709, #3834)

  > Contributed by Andrii Kostenko and George Psarakis.

- Redis Result Backend: Do not create PubSub subscriptions when results are ignored (#4709, #3834)

  > Contributed by Andrii Kostenko and George Psarakis.

- Redis Result Backend: Result consumer always unsubscribes when task state is ready (#4666)

  > Contributed by George Psarakis.

- Development/Testing: Add docker-compose and base Dockerfile for development (#4482)

  > Contributed by Chris Mitchell.

- Documentation/Sphinx: Teach autodoc to document tasks if undoc-members is not set (#4588)

  > Contributed by Leo Singer.

- Documentation/Sphinx: Put back undoc-members option in sphinx test (#4586)

  > Contributed by Leo Singer.

- Documentation/Sphinx: Sphinx autodoc picks up tasks automatically only if undoc-members is set (#4584)

  > Contributed by Leo Singer.

- Task: Fix shadow_name issue when using previous version Task class (#4572)

  > Contributed by @pachewise.

- Task: Add support for bound tasks as link_error parameter (Fixes #3723) (#4545)

  > Contributed by @brabiega.

- Deployment: Add a command line option for setting the Result Backend URL (#4549)

  > Contributed by @y0ngdi.

- CI: Enable pip cache in appveyor build (#4546)

  > Contributed by Thijs Triemstra.

- Concurrency/Asynpool: Fix errno property name shadowing.

  > Contributed by Omer Katz.

- DynamoDB Backend: Configurable endpoint URL (#4532)

  > Contributed by Bohdan Rybak.

- Timezones: Correctly detect UTC timezone and timezone from settings (Fixes #4517) (#4519)

  > Contributed by @last-partizan.

- Control: Cleanup the mailbox’s producer pool after forking (#4472)

  > Contributed by Nick Eaket.

- Documentation: Start Celery and Celery Beat on Azure WebJob (#4484)

  > Contributed by PauloPeres.

- Celery Beat: Schedule due tasks on startup, after Beat restart has occurred (#4493)

  > Contributed by Igor Kasianov.

- Worker: Use absolute time when task is accepted by worker pool (#3684)

  > Contributed by Régis Behmo.

- Canvas: Propagate arguments to chains inside groups (#4481)

  > Contributed by Chris Mitchell.

- Canvas: Fix Task.replace behavior in nested chords (fixes #4368) (#4369)

  > Contributed by Denis Shirokov & Alex Hill.

- Installation: Pass python_requires argument to setuptools (#4479)

  > Contributed by Jon Dufresne.

- Message Protocol Compatibility: Handle “hybrid” messages that have moved between Celery versions (#4358) (Issue #4356)

  > Contributed by Russell Keith-Magee.

- Canvas: request on_timeout now ignores soft time limit exception (fixes #4412) (#4473)

  > Contributed by Alex Garel.

- Redis Result Backend: Integration test to verify PubSub unsubscriptions (#4468)

  > Contributed by George Psarakis.

- Message Protocol Properties: Allow the shadow keyword argument and the shadow_name method to set shadow properly (#4381)

  > Contributed by @hclihn.

- Canvas: Run chord_unlock on same queue as chord body (#4448) (Issue #4337)

  > Contributed by Alex Hill.

- Canvas: Support chords with empty header group (#4443)

  > Contributed by Alex Hill.

- Timezones: make astimezone call in localize more safe (#4324)

  > Contributed by Matt Davis.

- Canvas: Fix length-1 and nested chords (#4437) (Issues #4393, #4055, #3885, #3597, #3574, #3323, #4301)

  > Contributed by Alex Hill.

- CI: Run Openstack Bandit in Travis CI in order to detect security issues.

  > Contributed by Omer Katz.

- CI: Run isort in Travis CI in order to lint Python import statements.

  > Contributed by Omer Katz.

- Canvas: Resolve TypeError on .get from nested groups (#4432) (Issue #4274)

  > Contributed by Misha Wolfson.

- CouchDB Backend: Correct CouchDB key string type for Python 2/3 compatibility (#4166)

  > Contributed by @fmind && Omer Katz.

- Group Result: Fix current_app fallback in GroupResult.restore() (#4431)

  > Contributed by Alex Hill.

- Consul Backend: Correct key string type for Python 2/3 compatibility (#4416)

  > Contributed by Wido den Hollander.

- Group Result: Correctly restore an empty GroupResult (#2202) (#4427)

  > Contributed by Alex Hill & Omer Katz.

- Result: Disable synchronous waiting for sub-tasks on eager mode(#4322)

  > Contributed by Denis Podlesniy.

- Celery Beat: Detect timezone or Daylight Saving Time changes (#1604) (#4403)

  > Contributed by Vincent Barbaresi.

- Canvas: Fix append to an empty chain. Fixes #4047. (#4402)

  > Contributed by Omer Katz.

- Task: Allow shadow to override task name in trace and logging messages. (#4379)

  > Contributed by @hclihn.

- Documentation/Sphinx: Fix getfullargspec Python 2.x compatibility in contrib/sphinx.py (#4399)

  > Contributed by Javier Martin Montull.

- Documentation: Updated installation instructions for SQS broker (#4382)

  > Contributed by Sergio Fernandez.

- Celery Beat: Better equality comparison for ScheduleEntry instances (#4312)

  > Contributed by @mariia-zelenova.

- Task: Adding ‘shadow’ property to as_task_v2 (#4350)

  > Contributed by Marcelo Da Cruz Pinto.

- Try to import directly, do not use deprecated imp method (#4216)

  > Contributed by Tobias Kunze.

- Task: Enable kwargsrepr and argsrepr override for modifying task argument representation (#4260)

  > Contributed by James M. Allen.

- Result Backend: Add Redis Sentinel backend (#4144)

  > Contributed by Geoffrey Bauduin.

- Use unique time values for Collections/LimitedSet (#3879 and #3891) (#3892)

  > Contributed by @lead2gold.

- CI: Report coverage for all result backends.

  > Contributed by Omer Katz.

- Django: Use Django DB max age connection setting (fixes #4116) (#4292)

  > Contributed by Marco Schweighauser.

- Canvas: Properly take into account chain tasks link_error (#4240)

  > Contributed by @agladkov.

- Canvas: Allow to create group with single task (fixes issue #4255) (#4280)

  > Contributed by @agladkov.

- Canvas: Copy dictionary parameter in chord.from_dict before modifying (fixes issue #4223) (#4278)

  > Contributed by @agladkov.

- Results Backend: Add Cassandra options (#4224)

  > Contributed by Scott Cooper.

- Worker: Apply rate limiting for tasks with ETA (#4251)

  > Contributed by @arpanshah29.

- Celery Beat: support scheduler entries without a schedule (#4235)

  > Contributed by Markus Kaiserswerth.

- SQS Broker: Updated SQS requirements file with correct boto3 version (#4231)

  > Contributed by Alejandro Varas.

- Remove unused code from _create_app contextmanager (#4204)

  > Contributed by Ryan P Kilby.

- Group Result: Modify GroupResult.as_tuple() to include parent (fixes #4106) (#4205)

  > Contributed by @pachewise.

- Beat: Set default scheduler class in beat command. (#4189)

  > Contributed by @Kxrr.

- Worker: Retry signal receiver after raised exception (#4192)

  > Contributed by David Davis.

- Task: Allow custom Request class for tasks (#3977)

  > Contributed by Manuel Vázquez Acosta.

- Django: Django fixup should close all cache backends (#4187)

  > Contributed by Raphaël Riel.

- Deployment: Adds stopasgroup to the supervisor scripts (#4200)

  > Contributed by @martialp.

- Using Exception.args to serialize/deserialize exceptions (#4085)

  > Contributed by Alexander Ovechkin.

- Timezones: Correct calculation of application current time with timezone (#4173)

  > Contributed by George Psarakis.

- Remote Debugger: Set the SO_REUSEADDR option on the socket (#3969)

  > Contributed by Theodore Dubois.

- Django: Celery ignores exceptions raised during django.setup() (#4146)

  > Contributed by Kevin Gu.

- Use heartbeat setting from application configuration for Broker connection (#4148)

  > Contributed by @mperice.

- Celery Beat: Fixed exception caused by next_transit receiving an unexpected argument. (#4103)

  > Contributed by DDevine.

- Task Introduce exponential backoff with Task auto-retry (#4101)

  > Contributed by David Baumgold.

- AsyncResult: Remove weak-references to bound methods in AsyncResult promises. (#4131)

  > Contributed by Vinod Chandru.

- Development/Testing: Allow eager application of canvas structures (#4576)

  > Contributed by Nicholas Pilon.

- Command Line: Flush stderr before exiting with error code 1.

  > Contributed by Antonin Delpeuch.

- Task: Escapes single quotes in kwargsrepr strings.

  > Contributed by Kareem Zidane

- AsyncResult: Restore ability to join over ResultSet after fixing celery/#3818.

  > Contributed by Derek Harland

- Redis Results Backend: Unsubscribe on message success.

  Previously Celery would leak channels, filling the memory of the Redis instance.

  Contributed by George Psarakis

- Task: Only convert eta to isoformat when it is not already a string.

  Contributed by Omer Katz

- Redis Results Backend: The result_backend setting now supports rediss:// URIs

  Contributed by James Remeika

- Canvas Keyword arguments are passed to tasks in chain as expected.

  Contributed by @tothegump

- Django Fix a regression causing Celery to crash when using Django.

  Contributed by Jonas Haag

- Canvas Chain with one task now runs as expected.

  Contributed by @tothegump

- Kombu Celery 4.2 now requires Kombu 4.2 or better.

  Contributed by Omer Katz & Asif Saifuddin Auvi

- GreenletExit is not in __all__ in greenlet.py which can not be imported by Python 3.6.

  The import was adjusted to work on Python 3.6 as well.

  Contributed by Hsiaoming Yang

- Fixed a regression that occurred during the development of Celery 4.2 which caused celery report to crash when Django is installed.

  Contributed by Josue Balandrano Coronel

- Matched the behavior of GroupResult.as_tuple() to that of AsyncResult.as_tuple().

  The group’s parent is now serialized correctly.

  Contributed by Josue Balandrano Coronel

- Use Redis coercion mechanism for converting URI query parameters.

  Contributed by Justin Patrin

- Fixed the representation of GroupResult.

  The dependency graph is now presented correctly.

  Contributed by Josue Balandrano Coronel

Documentation, CI, Installation and Tests fixes:

> - Sammie S. Taunton

> - Dan Wilson

> - @pachewise

> - Sergi Almacellas Abellana

> - Omer Katz

> - Alex Zaitsev

> - Leo Singer

> - Rachel Johnson

> - Jon Dufresne

> - Samuel Dion-Girardeau

> - Ryan Guest

> - Huang Huang

> - Geoffrey Bauduin

> - Andrew Wong

> - Mads Jensen

> - Jackie Leng

> - Harry Moreno

> - @michael-k

> - Nicolas Mota

> - Armenak Baburyan

> - Patrick Zhang

> - @anentropic

> - @jairojair

> - Ben Welsh

> - Michael Peake

> - Fengyuan Chen

> - @arpanshah29

> - Xavier Hardy

> - Shitikanth

> - Igor Kasianov

> - John Arnold

> - @dmollerm

> - Robert Knight

> - Asif Saifuddin Auvi

> - Eduardo Ramírez

> - Kamil Breguła

> - Juan Gutierrez