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From "Eric Newton (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7878) recoverFileLease does not check return value of recoverLease
Date Thu, 28 Mar 2013 13:57:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13616260#comment-13616260
] 

Eric Newton commented on HBASE-7878:
------------------------------------

Accumulo just writes out a LogEntry, which is a Writable.  Read-back just opens the file in
HDFS and starts reading LogEntrys.  It's slightly more complicated than that because we just
started to support encryption, so there's some metadata at the beginning of the file.

Accumulo uses a simpler file format to avoid the check for an empty file that occurs in SequenceFile.
HBase uses SequenceFileLogReader to work around the same issue.

But all this extra work might not be necessary now that we are properly closing the file.

                
> recoverFileLease does not check return value of recoverLease
> ------------------------------------------------------------
>
>                 Key: HBASE-7878
>                 URL: https://issues.apache.org/jira/browse/HBASE-7878
>             Project: HBase
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 0.95.0, 0.94.6
>            Reporter: Eric Newton
>            Assignee: Ted Yu
>            Priority: Critical
>             Fix For: 0.95.0, 0.98.0
>
>         Attachments: 7878.94, 7878-94.addendum, 7878-94.addendum2, 7878-addendum.txt,
7878-trunk.addendum, 7878-trunk.addendum2, 7878-trunk-v10.txt, 7878-trunk-v11-test.txt, 7878-trunk-v12.txt,
7878-trunk-v13.txt, 7878-trunk-v14.txt, 7878-trunk-v15.patch, 7878-trunk-v16.txt, 7878-trunk-v2.txt,
7878-trunk-v3.txt, 7878-trunk-v4.txt, 7878-trunk-v5.txt, 7878-trunk-v6.txt, 7878-trunk-v7.txt,
7878-trunk-v8.txt, 7878-trunk-v9.txt, 7878-trunk-v9.txt
>
>
> I think this is a problem, so I'm opening a ticket so an HBase person takes a look.
> Apache Accumulo has moved its write-ahead log to HDFS. I modeled the lease recovery for
Accumulo after HBase's lease recovery.  During testing, we experienced data loss.  I found
it is necessary to wait until recoverLease returns true to know that the file has been truly
closed.  In FSHDFSUtils, the return result of recoverLease is not checked. In the unit tests
created to check lease recovery in HBASE-2645, the return result of recoverLease is always
checked.
> I think FSHDFSUtils should be modified to check the return result, and wait until it
returns true.

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