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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 Tue, 19 May 2009 00:08:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710549#action_12710549
] 

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

My testing was done with hadoop 0.20.0 (I amended patch to work with 0.20 branch). 

Patch itself looks good.  Minor comments are

+ Is there anything that can be done about duplicated test condition in BlockManager.java
and DatanodeDescriptor.java.  Can the test be grouped up into a method that is used in both
places?
+ The if part of the if/else in DatanodeDescriptor.java is empty.  Put a comment here?  As
is, its hard to read.

I haven't played much with killing writer application and the local datanode.  Will try that
now.  Will also try confirm that we're reading up to the last sync before the kill.  Will
report back.

> 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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