[jira] [Commented] (HBASE-26596) region_mover should gracefully ignore null response from RSGroupAdmin#getRSGroupOfServer

["Yutong Xiao (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-26596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17463616#comment-17463616 ] 

Yutong Xiao commented on HBASE-26596:
-------------------------------------

Added a nil check in getSameRSGroupServers

{code:ruby}
# If the rsgroup is nil, that means this server belongs to no rsgroup.
  # It should be already offline.
  # So we just return and do nothing more.
  if rsgroup.nil?
    $LOG.warn("The server " + hostname + " belongs to no rsgroup. Is it already offline?")
    return results
  end
{code}
We can return an empty list. 
In unloadRegions if the returned server list is empty, it will exit. (/bin/region_mover.rb:324)





> region_mover should gracefully ignore null response from RSGroupAdmin#getRSGroupOfServer
> ----------------------------------------------------------------------------------------
>
>                 Key: HBASE-26596
>                 URL: https://issues.apache.org/jira/browse/HBASE-26596
>             Project: HBase
>          Issue Type: Bug
>          Components: mover, rsgroup
>    Affects Versions: 1.7.1
>            Reporter: Viraj Jasani
>            Assignee: Yutong Xiao
>            Priority: Major
>
> If regionserver has any non-daemon thread running even after it's own shutdown, the running non-daemon thread can prevent clean JVM exit and regionserver could be stuck in the zombie state. We have recently provided a workaround for this in HBASE-26468 for regionserver exit hook to wait 30s for all non-daemon threads to get stopped before terminating JVM abnormally.
> However, if regionserver is stuck in such state, region_mover unload fails with:
> {code:java}
> NoMethodError: undefined method `getName` for nil:NilClass
>   getSameRSGroupServers at /bin/region_mover.rb:503
>              __ensure__ at /bin/region_mover.rb:313 
>           unloadRegions at /bin/region_mover.rb:310               
>                  (root) at /bin/region_mover.rb:572               
>  {code}
> This happens if the cluster has RSGroup enabled and the given server is already stopped, hence RSGroupAdmin#getRSGroupOfServer would return null (as the server is not running anymore so it is not part of any RSGroup). region_mover should ride over this null response and gracefully exit from unloadRegions() call.
>  
> We should also check if the fix is applicable to branch-2 and above.



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