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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4379) In HDFS, sync() not yet guarantees data available to the new readers
Date Mon, 18 May 2009 23:56:46 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710546#action_12710546
] 

stack commented on HADOOP-4379:
-------------------------------

v9 works well in basic testing.  If I crash the writer application, a subsequent reader can
pick up edits from the crashed writer if the reader process does append, close and then reopen.

I've been trying to break the patch but it seems robust (v7 and v8 had issues that Dhruba
fixed).

The append/close process can take from 10-60 seconds in my basic testing.  Usually its about
20 seconds.  It would be better if there were no pause.  Can this be addressed?





> In HDFS, sync() not yet guarantees data available to the new readers
> --------------------------------------------------------------------
>
>                 Key: HADOOP-4379
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4379
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.19.2
>
>         Attachments: 4379_20081010TC3.java, fsyncConcurrentReaders.txt, fsyncConcurrentReaders3.patch,
fsyncConcurrentReaders4.patch, fsyncConcurrentReaders5.txt, fsyncConcurrentReaders6.patch,
fsyncConcurrentReaders9.patch, hypertable-namenode.log.gz, namenode.log, namenode.log, Reader.java,
Reader.java, reopen_test.sh, ReopenProblem.java, Writer.java, Writer.java
>
>
> In the append design doc (https://issues.apache.org/jira/secure/attachment/12370562/Appends.doc),
it says
> * A reader is guaranteed to be able to read data that was 'flushed' before the reader
opened the file
> However, this feature is not yet implemented.  Note that the operation 'flushed' is now
called "sync".

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