This document describes the current stable version of Celery (5.5). For development docs, go here.
celery.contrib.abortable
¶
Abortable Tasks.
Abortable tasks overview¶
For long-running Task
’s, it can be desirable to support
aborting during execution. Of course, these tasks should be built to
support abortion specifically.
The AbortableTask
serves as a base class for all Task
objects that should support abortion by producers.
Producers may invoke the
abort()
method onAbortableAsyncResult
instances, to request abortion.Consumers (workers) should periodically check (and honor!) the
is_aborted()
method at controlled points in their task’srun()
method. The more often, the better.
The necessary intermediate communication is dealt with by the
AbortableTask
implementation.
Usage example¶
In the consumer:
from celery.contrib.abortable import AbortableTask
from celery.utils.log import get_task_logger
from proj.celery import app
logger = get_logger(__name__)
@app.task(bind=True, base=AbortableTask)
def long_running_task(self):
results = []
for i in range(100):
# check after every 5 iterations...
# (or alternatively, check when some timer is due)
if not i % 5:
if self.is_aborted():
# respect aborted state, and terminate gracefully.
logger.warning('Task aborted')
return
value = do_something_expensive(i)
results.append(y)
logger.info('Task complete')
return results
In the producer:
import time
from proj.tasks import MyLongRunningTask
def myview(request):
# result is of type AbortableAsyncResult
result = long_running_task.delay()
# abort the task after 10 seconds
time.sleep(10)
result.abort()
After the result.abort() call, the task execution isn’t aborted immediately. In fact, it’s not guaranteed to abort at all. Keep checking result.state status, or call result.get(timeout=) to have it block until the task is finished.
Note
In order to abort tasks, there needs to be communication between the producer and the consumer. This is currently implemented through the database backend. Therefore, this class will only work with the database backends.
- class celery.contrib.abortable.AbortableAsyncResult(id, backend=None, task_name=None, app=None, parent=None)[source]¶
Represents an abortable result.
Specifically, this gives the AsyncResult a
abort()
method, that sets the state of the underlying Task to ‘ABORTED’.
- class celery.contrib.abortable.AbortableTask[source]¶
Task that can be aborted.
This serves as a base class for all
Task
’s that support aborting during execution.All subclasses of
AbortableTask
must call theis_aborted()
method periodically and act accordingly when the call evaluates toTrue
.- abstract = True¶
Deprecated attribute
abstract
here for compatibility.
- is_aborted(**kwargs)[source]¶
Return true if task is aborted.
Checks against the backend whether this
AbortableAsyncResult
isABORTED
.Always return
False
in case the task_id parameter refers to a regular (non-abortable)Task
.Be aware that invoking this method will cause a hit in the backend (for example a database query), so find a good balance between calling it regularly (for responsiveness), but not too often (for performance).