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celery.contrib.abortable

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 on AbortableAsyncResult instances, to request abortion.
• Consumers (workers) should periodically check (and honor!) the is_aborted() method at controlled points in their task’s run() 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

logger = get_logger(__name__)

class MyLongRunningTask(AbortableTask):

    def run(self, **kwargs):
        results = []
        for x in range(100):
            # Check after every 5 loops..
            if x % 5 == 0:  # alternatively, check when some timer is due
                if self.is_aborted(**kwargs):
                    # Respect the aborted status and terminate
                    # gracefully
                    logger.warning('Task aborted.')
                    return
            y = do_something_expensive(x)
            results.append(y)
        logger.info('Task finished.')
        return results

In the producer:

from myproject.tasks import MyLongRunningTask

def myview(request):

    async_result = MyLongRunningTask.delay()
    # async_result is of type AbortableAsyncResult

    # After 10 seconds, abort the task
    time.sleep(10)
    async_result.abort()

    ...

After the async_result.abort() call, the task execution is not aborted immediately. In fact, it is not guaranteed to abort at all. Keep checking the async_result status, or call async_result.wait() to have it block until the task is finished.

注解

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)

Represents a abortable result.

Specifically, this gives the AsyncResult a abort() method, which sets the state of the underlying Task to ‘ABORTED’.

abort()

Set the state of the task to ABORTED.

Abortable tasks monitor their state at regular intervals and terminate execution if so.

Be aware that invoking this method does not guarantee when the task will be aborted (or even if the task will be aborted at all).

is_aborted()

Return True if the task is (being) aborted.

class celery.contrib.abortable.AbortableTask

A celery task that serves as a base class for all Task‘s that support aborting during execution.

All subclasses of AbortableTask must call the is_aborted() method periodically and act accordingly when the call evaluates to True.

AsyncResult(task_id)

Return the accompanying AbortableAsyncResult instance.

is_aborted(**kwargs)

Checks against the backend whether this AbortableAsyncResult is ABORTED.

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).