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From "Alan Burlison (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3066) Hadoop leaves orphaned tasks running after job is killed
Date Wed, 27 May 2015 15:20:18 GMT

    [ https://issues.apache.org/jira/browse/YARN-3066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14561130#comment-14561130

Alan Burlison commented on YARN-3066:

Yes, that's a good point about not every platform having libhadoop. Solaris for example has
the syscall but not the executable, so in that case it's a better solution to use the syscall
but that's not always going to be the case.

> 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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