Celery task chain cancelling?

Question

I found that celery supports task chains: http://celery.readthedocs.org/en/latest/userguide/canvas.html#chains.

Question is: how can I stop chain's execution in a task?

For example, we got a chain of N items (N > 2). And in the second task we realize that we do not need all the rest tasks to be executed. What to do?

Answer 1

In newer versions of celery (3.1.6) you can revoke an entire chain by simply walking the chain and revoking each item in turn.

# Build a chain for results
from tasks import addd
from celery import chain

def revoke_chain(result):
    while result:
        result.revoke()
        result = result.parent

# independent tasks (with immutable signatures)
c = chain(*tuple(add.si(i,i) for i in xrange(50)))
h = c()

# some time later ...
revoke_chain(h)

# dependant task
c = add.s(1,1) | add.s(2) | add.s(3)
h = c()

# some time later ...
revoke_chain(h)