This document describes an older version of Celery (2.2). For the latest stable version please go here.
Signals allows decoupled applications to receive notifications when certain actions occur elsewhere in the application.
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license: | BSD, see LICENSE for more details. |
Several kinds of events trigger signals, you can connect to these signals to perform actions as they trigger.
Example connecting to the task_sent signal:
from celery.signals import task_sent
def task_sent_handler(sender=None, task_id=None, task=None, args=None,
kwargs=None, **kwds):
print("Got signal task_sent for task id %s" % (task_id, ))
task_sent.connect(task_sent_handler)
Some signals also have a sender which you can filter by. For example the task_sent signal uses the task name as a sender, so you can connect your handler to be called only when tasks with name “tasks.add” has been sent by providing the sender argument to connect:
task_sent.connect(task_sent_handler, sender="tasks.add")
Dispatched when a task has been sent to the broker. Note that this is executed in the client process, the one sending the task, not in the worker.
Sender is the name of the task being sent.
Provides arguments:
Id of the task to be executed.
The task being executed.
the tasks positional arguments.
The tasks keyword arguments.
The time to execute the task.
Id of the taskset this task is part of (if any).
Dispatched before a task is executed.
Sender is the task class being executed.
Provides arguments:
Id of the task to be executed.
The task being executed.
the tasks positional arguments.
The tasks keyword arguments.
Dispatched after a task has been executed.
Sender is the task class executed.
Provides arguments:
Id of the task to be executed.
The task being executed.
The tasks positional arguments.
The tasks keyword arguments.
The return value of the task.
Dispatched when a task fails.
Sender is the task class executed.
Provides arguments:
Id of the task.
Exception instance raised.
Positional arguments the task was called with.
Keyword arguments the task was called with.
Stack trace object.
The celery.datastructures.ExceptionInfo instance.
Dispatched before the worker is started.
Dispatched when the worker is ready to accept work.
Dispatched by each new pool worker process when it starts.
Dispatched when the worker is about to shut down.
Dispatched when celerybeat starts (either standalone or embedded). Sender is the celery.beat.Service instance.
Dispatched in addition to the beat_init signal when celerybeat is started as an embedded process. Sender is the celery.beat.Service instance.
Sent when the eventlet pool has been started.
Sender is the celery.concurrency.evlet.TaskPool instance.
Sent when the worker shutdown, just before the eventlet pool is requested to wait for remaining workers.
Sender is the celery.concurrency.evlet.TaskPool instance.
Sent when the pool has been joined and the worker is ready to shutdown.
Sender is the celery.concurrency.evlet.TaskPool instance.
Sent whenever a task is applied to the pool.
Sender is the celery.concurrency.evlet.TaskPool instance.
Provides arguments:
target
The target function.
args
Positional arguments.
kwargs
Keyword arguments.
Sent after the setup of every single task logger.
Provides arguments:
The logger object.
The level of the logging object.
The name of the logfile.
The log format string.
Specify if log messages are colored or not.
Sent after the setup of every global logger.
Provides arguments:
The logger object.
The level of the logging object.
The name of the logfile.
The log format string.
Specify if log messages are colored or not.