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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 08:10:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12602948#action_12602948
] 

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

bq. 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.

In an offline conversation I had with Mahadev, I actually found that he had meant the latter,
which is supported. So, all is good. The utility of the other feature remains, though it can
be done as an enhancement at a later state.

> 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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