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https://issues.apache.org/jira/browse/HADOOP-8353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13272448#comment-13272448
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Aaron T. Myers commented on HADOOP-8353:
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bq. The unfortunate truth there is that everything else in that script has a
YARN_ prefix (I suspect because it was copied from the yarn-daemon.sh). I'd
rather keep things consistent, but if you really think this lonely var should
be MR_ prefixed – please let me know.
Got it. Makes sense the way you have it.
bq. HDFS daemons use hadoop-daemon.sh In fact at this point it can be safely
called hdfs-daemon.sh since I don't think anything else is really using it.
Got it. Thanks for the explanation.
> hadoop-daemon.sh and yarn-daemon.sh can be misleading on stop
> -------------------------------------------------------------
>
> Key: HADOOP-8353
> URL: https://issues.apache.org/jira/browse/HADOOP-8353
> Project: Hadoop Common
> Issue Type: Improvement
> Components: scripts
> Affects Versions: 0.23.1
> Reporter: Roman Shaposhnik
> Assignee: Roman Shaposhnik
> Fix For: 2.0.0
>
> Attachments: HADOOP-8353.patch.txt
>
>
> The way that stop actions is implemented is a simple SIGTERM sent to the JVM.
> There's a time delay between when the action is called and when the process
> actually exists. This can be misleading to the callers of the *-daemon.sh
> scripts since they expect stop action to return when process is actually
> stopped.
> I suggest we augment the stop action with a time-delay check for the process
> status and a SIGKILL once the delay has expired.
> I understand that sending SIGKILL is a measure of last resort and is
> generally frowned upon among init.d script writers, but the excuse we have
> for Hadoop is that it is engineered to be a fault tolerant system and thus
> there's not danger of putting system into an incontinent state by a violent
> SIGKILL. Of course, the time delay will be long enough to make SIGKILL event
> a rare condition.
> Finally, there's always an option of an exponential back-off type of solution
> if we decide that SIGKILL timeout is short.
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