[jira] [Commented] (HBASE-12028) Abort the RegionServer, when one of it's handler threads die

["Sudarshan Kadambi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-12028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14140767#comment-14140767 ] 

Sudarshan Kadambi commented on HBASE-12028:
-------------------------------------------

It's also the case that if the handler thread exited because of any peculiarities in a given region (I'm still unclear about the root cause for HBASE-11813), moving that region off by aborting the RS, could end up taking down the entire cluster rather than keep it localized to a single RS. 

> Abort the RegionServer, when one of it's handler threads die
> ------------------------------------------------------------
>
>                 Key: HBASE-12028
>                 URL: https://issues.apache.org/jira/browse/HBASE-12028
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: Sudarshan Kadambi
>
> Over in HBase-11813, a user identified an issue where in all the RPC handler threads would exit with StackOverflow errors due to an unchecked recursion-terminating condition. Our clusters demonstrated the same trace. While the patch posted for HBASE-11813 got our clusters to be merry again, the breakdown surfaced some larger issues.
> When the RegionServer had all it's RPC handler threads dead, it continued to have regions assigned it. Clearly, it wouldn't be able to serve reads and writes on those regions. A second issue was that when a user tried to disable or drop a table, the master would try to communicate to the regionserver for region unassignment. Since the same handler threads seem to be used for master <-> RS communication as well, the master ended up hanging on the RS indefinitely. Eventually, the master stopped responding to all table meta-operations.
> A handler thread should never exit, and if it does, it seems like the more prudent thing to do would be for the RS to abort. This way, atleast recovery can be undertaken and the regions could be reassigned elsewhere. I also think that the master<->RS communication should get its own exclusive threadpool, but I'll wait until this issue has been sufficiently discussed before opening an issue ticket for that.



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