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POPython multiprocessing issue / misunderstanding
 

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  1. POPython multiprocessing issue / misunderstanding
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    <p>I'm having an issue with multiprocessing; I'm using python2.7 on linux 2.6.36. I know this would be much easier with a higher level module or library but I'm trying to use the lower level functions (os.fork() and os.exec*) to ensure I really understand- This is kind of a learning exercise.</p> <p>Below is my code, it's a multiprocessing 'ping' utility. The issue is while it seems to run, it throws an OSError every so often on the os.wait() line. "No child processes"</p> <p>That doesn't make sense to me as os.wait() should only be called when the program catches a signal that a child process has exited and needs to be reaped.</p> <p>Following the code is sample output.</p> <p>What am I doing wrong?</p> <pre><code>#!/usr/bin/python2.7 import os import time import sys import signal kids = [] def chldClean(SIG, FRM): global kids pid, status = os.wait() kids.pop(kids.index(pid)) signal.signal(signal.SIGCHLD, chldClean) hosts = ( '10.98.232.66', '10.86.144.241', '10.86.144.242', '10.98.193.130', '10.98.198.130', '10.86.116.161', '10.86.120.161', '10.99.21.254', '10.97.98.102', '10.97.111.180' ) while True: for HOST in hosts: while len(kids) &gt; 7: time.sleep(0.1) pid = os.fork() if pid == 0: os.closerange(0, 4) os.execl('/bin/ping', 'PING', '-c', '1', '-w', '2', HOST) else: kids.append(pid) print kids </code></pre> <p>Sample Output with Errors below ----------------------------------------</p> <pre><code>[18188] [18188, 18189] [18188, 18189, 18190] [18188, 18189, 18190, 18191] [18188, 18189, 18190, 18191, 18192] [18188, 18189, 18190, 18191, 18192, 18193] [18188, 18189, 18190, 18191, 18192, 18193, 18194] [18188, 18189, 18190, 18191, 18192, 18193, 18194, 18195] [18188, 18189, 18191, 18192, 18193, 18194, 18195, 18196] [18188, 18191, 18192, 18193, 18194, 18195, 18196, 18197] [18188, 18191, 18192, 18194, 18195, 18196, 18197, 18198] [18191, 18192, 18194, 18195, 18196, 18197, 18198, 18201] [18191, 18194, 18195, 18196, 18197, 18198, 18201, 18202] [18191, 18195, 18196, 18197, 18198, 18201, 18202, 18203] [18195, 18196, 18197, 18198, 18201, 18202, 18203, 18204] [18196, 18197, 18198, 18202, 18203, 18204, 18205] [18196, 18197, 18198, 18202, 18203, 18204, 18205, 18206] [18197, 18198, 18202, 18203, 18204, 18205, 18206, 18207] [18198, 18203, 18204, 18205, 18206, 18207, 18210] [18198, 18203, 18204, 18205, 18206, 18207, 18210, 18211] Traceback (most recent call last): File "./sunmon-mp", line 33, in &lt;module&gt; pid = os.fork() File "./sunmon-mp", line 12, in chldClean pid, status = os.wait() OSError: [Errno 10] No child processes [18203, 18204, 18205, 18206, 18207, 18210, 18211, 18212] [18203, 18204, 18206, 18207, 18210, 18211, 18212, 18213] [18203, 18204, 18206, 18207, 18211, 18212, 18213, 18214] [18203, 18204, 18206, 18207, 18211, 18212, 18214, 18215] [18203, 18204, 18206, 18207, 18212, 18214, 18215, 18217] [18203, 18204, 18206, 18207, 18214, 18215, 18217, 18218] [18203, 18204, 18206, 18207, 18215, 18217, 18218, 18219] [18204, 18206, 18207, 18215, 18217, 18218, 18219, 18220] [18204, 18206, 18207, 18217, 18218, 18219, 18220, 18221] [18206, 18207, 18217, 18218, 18219, 18220, 18221, 18223] [18207, 18217, 18218, 18219, 18220, 18221, 18223, 18224] [18217, 18218, 18219, 18220, 18221, 18223, 18224, 18225] [18217, 18219, 18220, 18221, 18223, 18224, 18225, 18226] [18217, 18219, 18220, 18221, 18223, 18225, 18226, 18227] [18217, 18219, 18220, 18221, 18223, 18226, 18227, 18228] [18217, 18220, 18221, 18223, 18226, 18227, 18228, 18229] [18217, 18220, 18221, 18223, 18227, 18228, 18229, 18230] [18217, 18220, 18221, 18223, 18227, 18228, 18230, 18231] [18220, 18221, 18223, 18227, 18228, 18230, 18231, 18233] [18221, 18223, 18227, 18228, 18230, 18231, 18233, 18234] [18223, 18227, 18228, 18230, 18231, 18233, 18234, 18235] [18223, 18227, 18228, 18231, 18233, 18234, 18235, 18236] [18223, 18227, 18228, 18231, 18233, 18234, 18236, 18237] [18223, 18227, 18228, 18231, 18233, 18234, 18237, 18239] [18227, 18228, 18231, 18233, 18234, 18237, 18239, 18240] [18228, 18231, 18233, 18234, 18237, 18239, 18240, 18241] [18228, 18231, 18233, 18237, 18239, 18240, 18241, 18242] [18231, 18233, 18237, 18239, 18240, 18241, 18242, 18243] [18231, 18233, 18239, 18240, 18241, 18242, 18243, 18244] [18231, 18233, 18239, 18240, 18242, 18243, 18244, 18245] [18231, 18233, 18239, 18242, 18243, 18244, 18245, 18246] [18231, 18233, 18242, 18243, 18244, 18245, 18246, 18247] [18233, 18242, 18243, 18244, 18245, 18246, 18247, 18248] [18242, 18243, 18244, 18245, 18246, 18247, 18248, 18249] [18243, 18244, 18245, 18246, 18247, 18248, 18249, 18250] [18243, 18245, 18246, 18247, 18248, 18249, 18250, 18251] [18243, 18245, 18247, 18248, 18249, 18250, 18251, 18252] [18243, 18245, 18248, 18249, 18250, 18251, 18252, 18253] [18243, 18245, 18249, 18250, 18251, 18252, 18253, 18254] [18243, 18245, 18249, 18250, 18252, 18253, 18254, 18255] [18245, 18249, 18250, 18252, 18253, 18254, 18255, 18258] [18249, 18250, 18252, 18253, 18254, 18255, 18258, 18259] [18249, 18250, 18253, 18254, 18255, 18258, 18259, 18260] [18249, 18250, 18253, 18254, 18255, 18258, 18260, 18261] [18249, 18250, 18253, 18254, 18255, 18260, 18261, 18262] [18250, 18253, 18254, 18255, 18260, 18261, 18262, 18263] [18253, 18254, 18255, 18260, 18261, 18262, 18263, 18264] [18253, 18254, 18255, 18261, 18262, 18263, 18264, 18265] [18253, 18254, 18255, 18261, 18262, 18264, 18265, 18266] [18254, 18255, 18261, 18262, 18264, 18265, 18266, 18267] [18255, 18261, 18262, 18264, 18265, 18266, 18267, 18268] [18261, 18262, 18264, 18265, 18266, 18267, 18268, 18269] [18261, 18262, 18265, 18266, 18267, 18268, 18269, 18270] [18261, 18262, 18265, 18266, 18267, 18268, 18270, 18271] [18261, 18262, 18265, 18266, 18267, 18270, 18271, 18273] [18261, 18262, 18265, 18266, 18270, 18271, 18273, 18274] [18261, 18262, 18265, 18266, 18271, 18273, 18274, 18275] [18261, 18262, 18265, 18266, 18271, 18273, 18275, 18276] [18262, 18265, 18266, 18271, 18273, 18275, 18276, 18277] [18262, 18265, 18266, 18273, 18275, 18276, 18277, 18278] [18265, 18266, 18273, 18276, 18277, 18278, 18280] [18265, 18266, 18273, 18276, 18277, 18278, 18280, 18281] Traceback (most recent call last): File "./sunmon-mp", line 33, in &lt;module&gt; pid = os.fork() File "./sunmon-mp", line 12, in chldClean pid, status = os.wait() OSError: [Errno 10] No child processes [18265, 18273, 18276, 18277, 18278, 18280, 18282] [18265, 18276, 18277, 18278, 18280, 18281, 18282, 18283] [18265, 18276, 18278, 18281, 18282, 18283, 18284] [18265, 18276, 18278, 18281, 18282, 18283, 18284, 18285] [18265, 18276, 18278, 18282, 18283, 18284, 18285, 18286] [18265, 18276, 18278, 18283, 18284, 18286, 18289] [18265, 18276, 18278, 18283, 18284, 18286, 18289, 18290] Traceback (most recent call last): File "./sunmon-mp", line 33, in &lt;module&gt; pid = os.fork() File "./sunmon-mp", line 12, in chldClean pid, status = os.wait() OSError: [Errno 10] No child processes [18265, 18276, 18278, 18283, 18284, 18289, 18290, 18291] [18276, 18278, 18283, 18284, 18289, 18290, 18291, 18292] [18276, 18278, 18283, 18284, 18290, 18291, 18292, 18293] [18276, 18278, 18283, 18284, 18290, 18291, 18293, 18294] [18276, 18278, 18283, 18284, 18290, 18291, 18294, 18295] [18278, 18283, 18284, 18290, 18291, 18294, 18295, 18297] [18283, 18284, 18290, 18291, 18294, 18295, 18297, 18298] [18283, 18284, 18290, 18291, 18295, 18297, 18298, 18299] </code></pre>
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      1. POPython multiprocessing issue / misunderstanding
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    1. COYou should use `#!/usr/bin/env python` instead of `#!/usr/bin/python2.7`
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    2. CODid you look up the "No child processes" error? If so, please reduce the size of your code (and output) to something small and focused. And include the definition you found of the "No child processes" error. Please **update** your question to be easier to read without scrolling.
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    3. CO@ThiefMaster the env python on this system is 3.1.3- i want to use python2.7 which is also on this system
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