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From "Dmitry Sivachenko (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-3066) Hadoop leaves orphaned tasks running after job is killed
Date Thu, 15 Jan 2015 14:18:34 GMT
Dmitry Sivachenko created YARN-3066:

             Summary: Hadoop leaves orphaned tasks running after job is killed
                 Key: YARN-3066
                 URL: https://issues.apache.org/jira/browse/YARN-3066
             Project: Hadoop YARN
          Issue Type: Bug
          Components: nodemanager
         Environment: Hadoop 2.4.1 (probably all later too), FreeBSD-10.1
            Reporter: Dmitry Sivachenko

When spawning user task, node manager checks for setsid(1) utility and spawns task program
via it. See hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java
for instance:

String exec = Shell.isSetsidAvailable? "exec setsid" : "exec";

FreeBSD, unlike Linux, does not have setsid(1) utility.  So plain "exec" is used to spawn
user task.  If that task spawns other external programs (this is common case if a task program
is a shell script) and user kills job via mapred job -kill <Job>, these child processes
remain running.

1) Why do you silently ignore the absence of setsid(1) and spawn task process via exec: this
is the guarantee to have orphaned processes when job is prematurely killed.
2) FreeBSD has a replacement third-party program called ssid (which does almost the same as
Linux's setsid).  It would be nice to detect which binary is present during configure stage
and put @SETSID@ macros into java file to use the correct name.

I propose to make Shell.isSetsidAvailable test more strict and fail to start if it is not
found:  at least we will know about the problem at start rather than guess why there are orphaned
tasks running forever.

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