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POpython multiprocessing.Pool kill *specific* long running or hung process
 

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  1. POpython multiprocessing.Pool kill *specific* long running or hung process
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    <p>I need to execute a pool of many parallel database connections and queries. I would like to use a multiprocessing.Pool or concurrent.futures ProcessPoolExecutor. Python 2.7.5</p> <p>In some cases, query requests take too long or will never finish (hung/zombie process). I would like to kill the <em>specific</em> process from the multiprocessing.Pool or concurrent.futures ProcessPoolExecutor that has timed out.</p> <p>Here is an example of how to kill/re-spawn the entire process pool, but ideally I would minimize that CPU thrashing since I only want to kill a specific long running process that has not returned data after timeout seconds.</p> <p>For some reason the code below does not seem to be able to terminate/join the process Pool after all results are returned and completed. It may have to do with killing worker processes when a timeout occurs, however the Pool creates new workers when they are killed and results are as expected.</p> <pre><code>from multiprocessing import Pool import time import numpy as np from threading import Timer import thread, time, sys def f(x): time.sleep(x) return x if __name__ == '__main__': pool = Pool(processes=4, maxtasksperchild=4) results = [(x, pool.apply_async(f, (x,))) for x in np.random.randint(10, size=10).tolist()] while results: try: x, result = results.pop(0) start = time.time() print result.get(timeout=5), '%d done in %f Seconds!' % (x, time.time()-start) except Exception as e: print str(e) print '%d Timeout Exception! in %f' % (x, time.time()-start) for p in pool._pool: if p.exitcode is None: p.terminate() pool.terminate() pool.join() </code></pre>
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