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From "Hong Tang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5478) Provide a node health check script and run it periodically to check the node health status
Date Tue, 16 Jun 2009 15:21:07 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5478?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720185#action_12720185

Hong Tang commented on HADOOP-5478:

bq Hong, is this to check if the TT is alive ? In which case, did you mean another signal,
like -0 or kill -3. -9 is SIGKILL and would kill the TT. Also, in that case are you suggesting
that we could keep the health checker around and continue trying to report after a while ?

@hemanth sorry for not being clear. I gave a bit more thoughts on the problem, and I think
the following logic may be simpler and more robust (1,2 are the current logic, 3 is my suggestion)

(1) periodically launch the health checking script; 
(2) reporting status that back to TT (both good and bad); 
(3) if it fails to receive response from TT, wait for X seconds, do an extra kill (to ensure
TT is dead), and quit itself. 

I scanned through the code, it seems that NodeHealthChecker.stop() would be a good place to
perform step (3).

> Provide a node health check script and run it periodically to check the node health status
> ------------------------------------------------------------------------------------------
>                 Key: HADOOP-5478
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5478
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>    Affects Versions: 0.20.0
>            Reporter: Aroop Maliakkal
>            Assignee: Sreekanth Ramakrishnan
>         Attachments: hadoop-5478-1.patch, hadoop-5478-2.patch, hadoop-5478-3.patch, hadoop-5478-4.patch,
> Hadoop must have some mechanism to find the health status of a node . It should run the
health check script periodically and if there is any errors, it should black list the node.
This will be really helpful when we run static mapred clusters. Else we may have to run some
scripts/daemons periodically to find the node status and take it offline manually.

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