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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2296) If read error while lease is being recovered, client reverts to stale view on block info
Date Sat, 10 Sep 2011 16:52:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13102081#comment-13102081
] 

Uma Maheswara Rao G commented on HDFS-2296:
-------------------------------------------

.
Thanks Stack, for filing the JIRA.

Do we need to make all read operations wait till the recovery completes?
(or) Lets provide an API from DFS to tell any recovery is in progress.So that the Apps can
make use of that API to know whether the given recovery request is completed or not. 

Any thoughts?

Todd & Jitendra, Any suggestions? Can you please give your opinions?


Thanks
Uma

> If read error while lease is being recovered, client reverts to stale view on block info
> ----------------------------------------------------------------------------------------
>
>                 Key: HDFS-2296
>                 URL: https://issues.apache.org/jira/browse/HDFS-2296
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 0.20-append, 0.22.0, 0.23.0
>            Reporter: stack
>            Priority: Critical
>
> We are seeing the following issue around recoverLease over in hbaselandia.  DFSClient
calls recoverLease to assume ownership of a file.  The recoverLease returns to the client
but it can take time for the new state to propagate.  Meantime, an incoming read fails though
its using updated block info.  Thereafter all read retries fail because on exception we revert
to stale block view and we never recover.  Laxman reports this issue in the below mailing
thread:
> See this thread for first report of this issue: http://search-hadoop.com/m/S1mOHFRmgk2/%2527FW%253A+Handling+read+failures+during+recovery%2527&subj=FW+Handling+read+failures+during+recovery
> Chatting w/ Hairong offline, she suggests this a general issue around lease recovery
no matter how it triggered (new recoverLease or not).
> I marked this critical.  At least over in hbase it is since we get set stuck here recovering
a crashed server.

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