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https://issues.apache.org/jira/browse/HBASE-2117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12801940#action_12801940
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Lars George commented on HBASE-2117:
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Quick update since I am currently working on JMX graphing and Nagios support
for HBase, I saw that Hadoop actually has it in place, the NameNode exposes
*numLiveDataNodes=INTEGER
*numDeadDataNodes=INTEGER
which are two JMX operations querying the numbers. In Nagios this would then be
checked against the known total number of nodes. I am opening an issue to add
this to the HBase Master too.
This is not to discourage you are slight the approach here, just saying that it
has its own merits and should be available as well.
> 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-v2.patch, 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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