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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2342) Consider adding a watchdog node next to region server
Date Sat, 20 Mar 2010 03:45:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12847705#action_12847705

stack commented on HBASE-2342:

On the possibility of scheduling an explicit defrag of the tenured generation:

from	Jon Masamitsu <Jon.Masamitsu@sun.com>
cc	hotspot-gc-use@openjdk.java.net
date	Fri, Mar 19, 2010 at 8:43 PM
subject	Re: Using CMS, any chance of forewarning a serial full GC is imminent?
System.gc() will cause CMS to do a full collection.  Does that
help?  As long as you have not turned off explicit GC's nor
set flags so that CMS does System.gc() concurrently, you can
compact the tenured (CMS) gen that way.

> Consider adding a watchdog node next to region server
> -----------------------------------------------------
>                 Key: HBASE-2342
>                 URL: https://issues.apache.org/jira/browse/HBASE-2342
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: regionserver
>            Reporter: Todd Lipcon
> This idea has been bandied about a fair amount. The concept is to add a second java process
that runs next to each region server to act as a watchdog. Several possible purposes:
> - monitor the RS for liveness - if it exhibits Juliet syndrome ("appears dead") then
we kill it agressively to prevent it from coming back to life
> - restart RS automatically in failure cases
> - potentially move the entire ZK session to the watchdog to decouple node liveness from
the particular JVM liveness
> Let's discuss in this JIRA.

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