[jira] [Commented] (YARN-3066) Hadoop leaves orphaned tasks running after job is killed

["Chris Nauroth (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-3066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14279202#comment-14279202 ] 

Chris Nauroth commented on YARN-3066:
-------------------------------------

I'm not familiar with {{ssid}} on FreeBSD.  Does it have the same usage as Linux {{setsid}}?  If so, then perhaps an appropriate workaround is to copy that binary to {{setsid}} and make sure it's available on the {{PATH}}.  This might not require any YARN code changes.

bq. I propose to make Shell.isSetsidAvailable test more strict and fail to start if it is not found.

This would likely have to be considered backwards-incompatible, because applications would fail to start on existing systems that don't have {{setsid}}.  I suppose the new behavior could be hidden behind an opt-in configuration property.  Also, we need to keep in mind that {{Shell.isSetsidAvailable}} is always {{false}} on Windows.  (On Windows, we handle the issue of orphaned processes by using Windows API job objects instead of {{setsid}}.)

> 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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