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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-2719) Corner case exists in detecting Java process deaths that might lead to orphan pipes processes lying around in memory
Date Mon, 28 Jan 2008 06:49:34 GMT
Corner case exists in detecting Java process deaths that might lead to orphan pipes processes
lying around in memory
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                 Key: HADOOP-2719
                 URL: https://issues.apache.org/jira/browse/HADOOP-2719
             Project: Hadoop Core
          Issue Type: Bug
          Components: pipes
    Affects Versions: 0.16.0
            Reporter: Devaraj Das
            Priority: Minor
             Fix For: 0.17.0


In HADOOP-2092, the child pipes process periodically pings the parent Java process to find
out whether it is alive. The ping cycle is 5 seconds. Consider the following scenario:
1) The Java task dies at the beginning of the ping cycle
2) A new Java task starts and binds to the same port as the earlier Java task's port
3) The pipes process wakes up and does a ping - it will still be successful since the port
number hasn't changed
This will lead to orphan processes lying around in memory. The detection of parent process
deaths can be made more reliable at least on Unix'ish platforms by checking whether the parent
process ID is 1, and if so exit. This will take care of the most common platform that hadoop
is run on. For non-unix platforms, the existing ping mechanism can be retained. Thoughts?

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