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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2940) Improve behavior under partial failure of region servers
Date Mon, 30 Aug 2010 00:55:53 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12904058#action_12904058
] 

Ted Yu commented on HBASE-2940:
-------------------------------

Since hbase.rootdir points to hadoop namenode, HBase Master can poll hadoop for the live data
nodes. If a data node comes down for longer than specified duration and a RS happens to be
on the same server, Master can blacklist that RS (assuming there is problem with heartbeat
from that RS in the same time period).

> Improve behavior under partial failure of region servers
> --------------------------------------------------------
>
>                 Key: HBASE-2940
>                 URL: https://issues.apache.org/jira/browse/HBASE-2940
>             Project: HBase
>          Issue Type: New Feature
>          Components: master, regionserver
>            Reporter: Todd Lipcon
>
> On larger clusters, we often see failure cases where a server is "up" (ie heartbeating)
but unable to actually service requests properly (or at a reasonable speed). This can happen
for any number of reasons including:
> - failing disks or disk controllers respond, but do so very slowly
> - the machine is swapping, so everything is still running but much more slowly than expected
> - HBase or the DN on the machine has been misconfigured (eg missing lzo libs) so it fails
to correctly open regions, perform flushes, etc.
> Here are a few proposed features that are worth considering:
> 1) Add a "blacklist" or "remote shutdown" functionality to the master. This is useful
if the region server is up but for some reason the admin can't ssh in to shut it down (eg
the root disk has failed). This feature would allow the admin to issue a command that will
shut down any given RS.
> 2) Periodically run a "health check" script on the region server node. If the script
returns an error code, the RS could shut itself down gracefully and report an error message
on the master console.
> 3) Allow clients to report back RS-specific errors to the master. This would be useful
for monitoring, and we could add heuristics to automatically shut down region servers if they
have an elevated error count over some period of time.

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