This document describes Celery 2.3. For development docs, go here.

celery.app.task

class celery.app.task.TaskType

Meta class for tasks.

Automatically registers the task in the task registry, except if the abstract attribute is set.

If no name attribute is provided, then no name is automatically set to the name of the module it was defined in, and the class name.

class celery.app.task.BaseTask

Task base class.

When called tasks apply the run() method. This method must be defined by all tasks (that is unless the __call__() method is overridden).

classmethod AsyncResult(task_id)

Get AsyncResult instance for this kind of task.

Parameters:task_id – Task id to get result for.
exception MaxRetriesExceededError

The tasks max restart limit has been exceeded.

BaseTask.abstract = None

If True the task is an abstract base class.

BaseTask.accept_magic_kwargs = False

If disabled the worker will not forward magic keyword arguments. Deprecated and scheduled for removal in v3.0.

BaseTask.acks_late = False

When enabled messages for this task will be acknowledged after the task has been executed, and not just before which is the default behavior.

Please note that this means the task may be executed twice if the worker crashes mid execution (which may be acceptable for some applications).

The application default can be overridden with the CELERY_ACKS_LATE setting.

BaseTask.after_return(status, retval, task_id, args, kwargs, einfo)

Handler called after the task returns.

Parameters:
  • status – Current task state.
  • retval – Task return value/exception.
  • task_id – Unique id of the task.
  • args – Original arguments for the task that failed.
  • kwargs – Original keyword arguments for the task that failed.
  • einfoExceptionInfo instance, containing the traceback (if any).

The return value of this handler is ignored.

BaseTask.app = None

The application instance associated with this task class.

classmethod BaseTask.apply(args=None, kwargs=None, **options)

Execute this task locally, by blocking until the task returns.

Parameters:
  • args – positional arguments passed on to the task.
  • kwargs – keyword arguments passed on to the task.
  • throw – Re-raise task exceptions. Defaults to the CELERY_EAGER_PROPAGATES_EXCEPTIONS setting.

:rtype celery.result.EagerResult:

classmethod BaseTask.apply_async(args=None, kwargs=None, countdown=None, eta=None, task_id=None, publisher=None, connection=None, connect_timeout=None, router=None, expires=None, queues=None, **options)

Apply tasks asynchronously by sending a message.

Parameters:
  • args – The positional arguments to pass on to the task (a list or tuple).
  • kwargs – The keyword arguments to pass on to the task (a dict)
  • countdown – Number of seconds into the future that the task should execute. Defaults to immediate execution (do not confuse with the immediate flag, as they are unrelated).
  • eta – A datetime object describing the absolute time and date of when the task should be executed. May not be specified if countdown is also supplied. (Do not confuse this with the immediate flag, as they are unrelated).
  • expires – Either a int, describing the number of seconds, or a datetime object that describes the absolute time and date of when the task should expire. The task will not be executed after the expiration time.
  • connection – Re-use existing broker connection instead of establishing a new one. The connect_timeout argument is not respected if this is set.
  • connect_timeout – The timeout in seconds, before we give up on establishing a connection to the AMQP server.
  • retry – If enabled sending of the task message will be retried in the event of connection loss or failure. Default is taken from the CELERY_TASK_PUBLISH_RETRY setting. Note you need to handle the publisher/connection manually for this to work.
  • retry_policy – Override the retry policy used. See the CELERY_TASK_PUBLISH_RETRY setting.
  • routing_key – The routing key used to route the task to a worker server. Defaults to the routing_key attribute.
  • exchange – The named exchange to send the task to. Defaults to the exchange attribute.
  • exchange_type – The exchange type to initialize the exchange if not already declared. Defaults to the exchange_type attribute.
  • immediate – Request immediate delivery. Will raise an exception if the task cannot be routed to a worker immediately. (Do not confuse this parameter with the countdown and eta settings, as they are unrelated). Defaults to the immediate attribute.
  • mandatory – Mandatory routing. Raises an exception if there’s no running workers able to take on this task. Defaults to the mandatory attribute.
  • priority – The task priority, a number between 0 and 9. Defaults to the priority attribute.
  • serializer – A string identifying the default serialization method to use. Can be pickle, json, yaml, msgpack or any custom serialization method that has been registered with kombu.serialization.registry. Defaults to the serializer attribute.
  • compression – A string identifying the compression method to use. Can be one of zlib, bzip2, or any custom compression methods registered with kombu.compression.register(). Defaults to the CELERY_MESSAGE_COMPRESSION setting.

Note

If the CELERY_ALWAYS_EAGER setting is set, it will be replaced by a local apply() call instead.

BaseTask.autoregister = True

If disabled this task won’t be registered automatically.

BaseTask.backend = None

The result store backend used for this task.

BaseTask.default_retry_delay = 180

Default time in seconds before a retry of the task should be executed. 3 minutes by default.

classmethod BaseTask.delay(*args, **kwargs)

Star argument version of apply_async().

Does not support the extra options enabled by apply_async().

Parameters:
  • *args – positional arguments passed on to the task.
  • **kwargs – keyword arguments passed on to the task.

:returns celery.result.AsyncResult:

BaseTask.delivery_mode = None

Override the apps default delivery mode for this task. Default is “persistent”, but you can change this to “transient”, which means messages will be lost if the broker is restarted. Consult your broker manual for any additional delivery modes.

BaseTask.error_whitelist = ()

List of exception types to send error emails for.

classmethod BaseTask.establish_connection(connect_timeout=None)

Establish a connection to the message broker.

BaseTask.exchange = None

Overrides the apps default exchange for this task.

BaseTask.exchange_type = None

Overrides the apps default exchange type for this task.

BaseTask.execute(request, pool, loglevel, logfile, **kwargs)

The method the worker calls to execute the task.

Parameters:
  • request – A TaskRequest.
  • pool – A task pool.
  • loglevel – Current loglevel.
  • logfile – Name of the currently used logfile.
  • consumer – The Consumer.
BaseTask.expires = None

Default task expiry time.

classmethod BaseTask.get_consumer(connection=None, connect_timeout=None)

Get message consumer.

:rtype kombu.messaging.Consumer:

Warning

If you don’t specify a connection, one will automatically be established for you, in that case you need to close this connection after use:

>>> consumer = self.get_consumer()
>>> # do something with consumer
>>> consumer.close()
>>> consumer.connection.close()
classmethod BaseTask.get_logger(loglevel=None, logfile=None, propagate=False, **kwargs)

Get task-aware logger object.

classmethod BaseTask.get_publisher(connection=None, exchange=None, connect_timeout=None, exchange_type=None, **options)

Get a celery task message publisher.

:rtype TaskPublisher:

Warning

If you don’t specify a connection, one will automatically be established for you, in that case you need to close this connection after use:

>>> publisher = self.get_publisher()
>>> # ... do something with publisher
>>> publisher.connection.close()

or used as a context:

>>> with self.get_publisher() as publisher:
...     # ... do something with publisher
BaseTask.ignore_result = False

If enabled the worker will not store task state and return values for this task. Defaults to the CELERY_IGNORE_RESULT setting.

BaseTask.immediate = False

Request immediate delivery.

BaseTask.mandatory = False

Mandatory message routing.

BaseTask.max_retries = 3

Maximum number of retries before giving up. If set to None, it will never stop retrying.

BaseTask.name = None

Name of the task.

BaseTask.on_failure(exc, task_id, args, kwargs, einfo)

Error handler.

This is run by the worker when the task fails.

Parameters:
  • exc – The exception raised by the task.
  • task_id – Unique id of the failed task.
  • args – Original arguments for the task that failed.
  • kwargs – Original keyword arguments for the task that failed.
  • einfoExceptionInfo instance, containing the traceback.

The return value of this handler is ignored.

BaseTask.on_retry(exc, task_id, args, kwargs, einfo)

Retry handler.

This is run by the worker when the task is to be retried.

Parameters:
  • exc – The exception sent to retry().
  • task_id – Unique id of the retried task.
  • args – Original arguments for the retried task.
  • kwargs – Original keyword arguments for the retried task.
  • einfoExceptionInfo instance, containing the traceback.

The return value of this handler is ignored.

BaseTask.on_success(retval, task_id, args, kwargs)

Success handler.

Run by the worker if the task executes successfully.

Parameters:
  • retval – The return value of the task.
  • task_id – Unique id of the executed task.
  • args – Original arguments for the executed task.
  • kwargs – Original keyword arguments for the executed task.

The return value of this handler is ignored.

BaseTask.priority = None

Default message priority. A number between 0 to 9, where 0 is the highest. Note that RabbitMQ does not support priorities.

BaseTask.queue = None

Destination queue. The queue needs to exist in CELERY_QUEUES. The routing_key, exchange and exchange_type attributes will be ignored if this is set.

BaseTask.rate_limit = None

Rate limit for this task type. Examples: None (no rate limit), “100/s” (hundred tasks a second), “100/m” (hundred tasks a minute),`”100/h”` (hundred tasks an hour)

BaseTask.request = <celery.app.task.Context object at 0x5a68460>

Request context (set when task is applied).

classmethod BaseTask.retry(args=None, kwargs=None, exc=None, throw=True, eta=None, countdown=None, max_retries=None, **options)

Retry the task.

Parameters:
  • args – Positional arguments to retry with.
  • kwargs – Keyword arguments to retry with.
  • exc – Optional exception to raise instead of MaxRetriesExceededError when the max restart limit has been exceeded.
  • countdown – Time in seconds to delay the retry for.
  • eta – Explicit time and date to run the retry at (must be a datetime instance).
  • max_retries – If set, overrides the default retry limit.
  • **options – Any extra options to pass on to meth:apply_async.
  • throw – If this is False, do not raise the RetryTaskError exception, that tells the worker to mark the task as being retried. Note that this means the task will be marked as failed if the task raises an exception, or successful if it returns.
Raises celery.exceptions.RetryTaskError:
 

To tell the worker that the task has been re-sent for retry. This always happens, unless the throw keyword argument has been explicitly set to False, and is considered normal operation.

Example

>>> @task
>>> def tweet(auth, message):
...     twitter = Twitter(oauth=auth)
...     try:
...         twitter.post_status_update(message)
...     except twitter.FailWhale, exc:
...         # Retry in 5 minutes.
...         return tweet.retry(countdown=60 * 5, exc=exc)

Although the task will never return above as retry raises an exception to notify the worker, we use return in front of the retry to convey that the rest of the block will not be executed.

BaseTask.routing_key = None

Overrides the apps default routing_key for this task.

BaseTask.run(*args, **kwargs)

The body of the task executed by workers.

BaseTask.send_error_emails = False

If enabled an email will be sent to ADMINS whenever a task of this type fails.

BaseTask.serializer = 'pickle'

The name of a serializer that are registered with kombu.serialization.registry. Default is “pickle”.

BaseTask.soft_time_limit = None

Soft time limit. Defaults to the CELERY_TASK_SOFT_TIME_LIMIT setting.

BaseTask.store_errors_even_if_ignored = False

When enabled errors will be stored even if the task is otherwise configured to ignore results.

classmethod BaseTask.subtask(*args, **kwargs)

Returns subtask object for this task, wrapping arguments and execution options for a single task invocation.

BaseTask.time_limit = None

Hard time limit. Defaults to the CELERY_TASK_TIME_LIMIT setting.

BaseTask.track_started = False

If enabled the task will report its status as “started” when the task is executed by a worker. Disabled by default as the normal behaviour is to not report that level of granularity. Tasks are either pending, finished, or waiting to be retried.

Having a “started” status can be useful for when there are long running tasks and there is a need to report which task is currently running.

The application default can be overridden using the CELERY_TRACK_STARTED setting.

BaseTask.type = 'regular'

The type of task (no longer used).

BaseTask.update_state(task_id=None, state=None, meta=None)

Update task state.

Parameters:
  • task_id – Id of the task to update.
  • state – New state (str).
  • meta – State metadata (dict).

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