Implementing a timeout on a multiprocessing process in Python

Question

I do:

import multiprocessing as mp
q = mp.Queue()
p = mp.Process(target=lambda x: x, args=('foo',))
p.start()
p.join(10)
if p.exitcode == 0:
   q.get()
else:
   print("We timed out.")

What I expect is that my tiny x->x function will block for at most 10 seconds. If it finished before then, I get the result sooner than that. If it takes longer than that (obviously not in this toy example, but in other cases), then the process terminates after 10 seconds and I am able to check exitcode to determine that we have indeed timed out.

But when I execute this code, what happens instead is that q.get() runs forever. Why does this occur?

Torkel Bjørnson-Langen · Accepted Answer · 2017-05-28 22:38:28Z

1

q.get() runs forever since it blocks by default, and you never put anything into the queue.

You can use q.get(block=False) or q.get_nowait() (which is equivalent to the former). But remember that it will raise queue.Empty, so you should handle that.

answered May 28, 2017 at 22:38

Torkel Bjørnson-Langen

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