[jira] Commented: (HBASE-2117) Simple check on the master overview page if the number of currently running regionservers is unchanged.

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

    [ https://issues.apache.org/jira/browse/HBASE-2117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12799286#action_12799286 ] 

stack commented on HBASE-2117:
------------------------------

Thanks for the patch.

While its true that the regionserver file will usually list all members of a cluster, on occasion it may lag what is actually up and running: e.g. up on ec2, I believe the regionserver file is not in alignment with what servers make up the cluster.  So, rather than identifying the mismatch between actual cluster members and content of the regionserver file as an ERROR, rather, I'd suggest it should be couched as a gentle hint that the two are not in alignment.  Admins should be able to easily ignore this message for the case where they have intentionally misaligned the two.  On the other hand, a gentle prompting could be handy reminder that a newly added regionserver needs to be added to the regionserver file if the admin wants it started as part of general cluster restart next time around.

> Simple check on the master overview page if the number of currently running regionservers is unchanged.
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-2117
>                 URL: https://issues.apache.org/jira/browse/HBASE-2117
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: master, regionserver
>    Affects Versions: 0.20.2
>            Reporter: Ferdy
>         Attachments: HBASE-2117.patch
>
>
> Incidentally, it happens that some of our regionservers just stop working. The regionserver logs show some sort of termination and the affected regionserver is just removed from the master page. Besides the actual problem of the termination, what I was missing was some sort of warning (from either running client code or the master page) that some regionservers are having trouble.
> It seems like the Master is ok with the fact that a regionserver suddenly decides to stop. The result is that the clients depending on the data in Hbase will be presented an incomplete data set, at least as long as the failing regions are not re-assigned yet. In order to have this monitored, I decided to create a patch that exposes an extra piece of information on the master page. An 'OK:' is presented if the current number of regionservers is unchanged since the start of the processes. An 'ERROR:' is shown whenever the current number is not the same. What the master page does is reading the 'regionservers' file once, and remember the number of slaves so that is can be used in the check. (So afterwards changes to this file are not supported).
> Perhaps this is not the right way of doing things. Please let me know if there are any existing solutions for these issues.
> I will attach a patch right away.

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