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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3184) HOD gracefully exclude "bad" nodes during ring formation
Date Fri, 06 Jun 2008 06:00:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12602929#action_12602929
] 

Hemanth Yamijala commented on HADOOP-3184:
------------------------------------------

Mahadev, thank you for the review.

bq. 1) shouldRetryMasterLaunch is defined but is not used anywhere

This is removed now.

bq. 2) you might want to wrap around most the statements since they exceed 80 character columns.

Also done.

bq. 3) is there something we can report back to the user on the command line that some machines
are faultty - CRITICAL contact admin? it would be really helpful if we can do that .

I presume you mean in the case where some machines failed, but the cluster eventually came
up, right ? Because otherwise, we do print a report on the command line for the users that
the hodring on this machine failed due to this reason. The services folks could then check
the ringmaster log to see what other machines failed. 

If you meant the former (i.e. the case of eventual success), I agree that it would be useful
feature to have. However, it would take more work to build this functionality into the client.
I propose we leave this as such for now, and make the enhancement in a later release.

> HOD gracefully exclude "bad" nodes during ring formation
> --------------------------------------------------------
>
>                 Key: HADOOP-3184
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3184
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/hod
>            Reporter: Marco Nicosia
>            Assignee: Hemanth Yamijala
>             Fix For: 0.18.0
>
>         Attachments: 3184.1.patch, 3184.2.patch
>
>
> HOD clusters sometimes fail to allocate due to a single "bad" node. During ring formation,
the entire ring should not be dependent upon every single node being good. Instead, it should
either exclude any ring member that does not adequately join the ring in a specified amount
of time.
> This is a frequent HOD user issue (although not directly caused by HOD).
> Examples of bad nodes: Missing java, incorrect version of HOD or Hadoop, local name-cache
corrupt, slow network links, drives just beginning to fail, etc.
> Many of these conditions are known, and we can monitor for those separately, but this
enhancement would shield users from unknown failure conditions that we haven't yet anticipated.
This way, a user will get a cluster, instead of hanging indefinitely.

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