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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 Thu, 28 May 2009 20:53:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714168#action_12714168
] 

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

In this test run, the append never succeeds.... or at least, after 25 minutes it still has
not successfully done the append open.  We try the append, fail with an AlreadyBeingCreatedException,
sleep a second, and then cycle.  Usually it takes well under a minute to successfully open-to-append.
 Namenode log is here: www.duboce.net:~stack/wontstop_namenode.log.gz.  In this case, I killed
datanode and the hbase regionserver simulating a machine falling off the cluster (Previous,
I was mostly just killing the server process and not the datanode).

> 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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