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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4379) In HDFS, sync() not yet guarantees data available to the new readers
Date Wed, 25 Feb 2009 23:33:02 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12676816#action_12676816
] 

Jim Kellerman commented on HADOOP-4379:
---------------------------------------

Applying this patch to hadoop-0.19.0, it does work, but slowly:

It takes almost an hour to recover the lease of a file when the hdfs cluster is under load:

{code}
2009-02-25 21:39:16,843 DEBUG org.apache.hadoop.hbase.regionserver.HLog: Splitting 3 of 3:
hdfs://aa0-000-12.u.powerset.com:8100/hbase/log_208.76.44.139_1235597506284_8020/hlog.dat.1235597820662
2009-02-25 21:39:16,847 DEBUG org.apache.hadoop.hbase.regionserver.HLog: Triggering lease
recovery.
...
2009-02-25 22:37:12,755 INFO org.apache.hadoop.hbase.regionserver.HLog: log file splitting
completed for hdfs://aa0-000-12.u.powerset.com:8100/hbase/log_208.76.44.139_1235597506284_8020
{code}


> 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, 0.20.0
>
>         Attachments: 4379_20081010TC3.java, fsyncConcurrentReaders.txt, fsyncConcurrentReaders3.patch,
fsyncConcurrentReaders4.patch, hypertable-namenode.log.gz, 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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