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https://issues.apache.org/jira/browse/HDFS-4526?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uma Maheswara Rao G updated HDFS-4526:
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Attachment: HDFS-4526.patch
Here is a simple patch to just return if persistsBlocks already enabled.
> If persistBlocks enabled in Namenode, hflush call can avoid persisting blocks
> with fsync
> ----------------------------------------------------------------------------------------
>
> Key: HDFS-4526
> URL: https://issues.apache.org/jira/browse/HDFS-4526
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.0.0, 2.0.3-alpha
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
> Attachments: HDFS-4526.patch
>
>
> If persists blocks enabled/in HA, evenry getAdditionalBlock will persist the
> blocks.
> So, if user calls Hflush, then client can simply ensure data flushed to DNs
> and need not worry about fsync.
> Since we can not depend upon client side configuration about persistBlocks,
> we can just make a fsync call to NN and check whether persistBlocks enabled.
> If it is enabled, then simply return as it would have already persisted. So,
> that below peice of code execution can be avoided for every blocks and hflush
> calls
> from fsync:
> {code}
> writeLock();
> try {
> checkOperation(OperationCategory.WRITE);
> if (isInSafeMode()) {
> throw new SafeModeException("Cannot fsync file " + src, safeMode);
> }
> INodeFileUnderConstruction pendingFile = checkLease(src, clientName);
> dir.persistBlocks(src, pendingFile);
> } finally {
> writeUnlock();
> }
> getEditLog().logSync();
> {code}
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