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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2288) Replicas awaiting recovery should return a full visible length
Date Tue, 13 Sep 2011 03:22:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13103299#comment-13103299
] 

Todd Lipcon commented on HDFS-2288:
-----------------------------------

Hi Konstantin. Thanks for taking a look at this. I didn't flesh out the scenario quite enough:

- Writer is writing to a pipeline, alternating writes and hflush()
- A concurrent reader is reading from the replicas (just behind the writer). Thus maybe it
sees 30MB out of the 64MB block in progress.
- The writer and the three DNs crash/restart
- The reader continues trying to read, and is now unable to see the data they previously saw,
until lease recovery proceeds (many minutes)

This seems incorrect. I think the reason it's not mentioned in the design doc is that the
design didn't cover all the cases of concurrent readers behind writers.

> Replicas awaiting recovery should return a full visible length
> --------------------------------------------------------------
>
>                 Key: HDFS-2288
>                 URL: https://issues.apache.org/jira/browse/HDFS-2288
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.23.0
>
>         Attachments: hdfs-2288.txt
>
>
> Currently, if the client calls getReplicaVisibleLength for a RWR, it returns a visible
length of 0. This causes one of HBase's tests to fail, and I believe it's incorrect behavior.

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