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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-9086) Enforce process singleton rules through an exclusive write lock on a file, not a pid file +kill -0,
Date Fri, 23 Nov 2012 11:08:58 GMT
Steve Loughran created HADOOP-9086:
--------------------------------------

             Summary: Enforce process singleton rules through an exclusive write lock on a
file, not a pid file +kill -0,
                 Key: HADOOP-9086
                 URL: https://issues.apache.org/jira/browse/HADOOP-9086
             Project: Hadoop Common
          Issue Type: Improvement
          Components: util
    Affects Versions: 1.1.1, 2.0.3-alpha
         Environment: Unix/Linux. 
            Reporter: Steve Loughran


the {{hadoop-daemon.sh}} script (and other liveness monitors) probe the existence of a daemon
service by a {{kill -0}} of a process id picked up from a pid file. 
This is flawed
# pid file locations may change with installations.
# Linux and Unix recycle pids, leading to false positives -the scripts think the process is
running, when another process is.
# doesn't work on windows.

Having the processes acquire an exclusive write-lock on a known file would delegate lock management
and implicitly liveness to the OS itself. when the process dies, the lock is relased (on Unixes)

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