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Date: Sat, 12 May 2012 05:09:50 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Updated] (HDFS-744) Support hsync in HDFS
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     [ https://issues.apache.org/jira/browse/HDFS-744?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lars Hofhansl updated HDFS-744:
-------------------------------

    Attachment: HDFS-744-trunk-v3.patch

Most tests fail due to an NPE in flush.
currentPacket can be null in DFSOutputStream.{hflush|hsync} even when bytesCurBlock > lastFlushOffset, which I found a bit surprising.
I think in that case it is OK not to send a sync packet (if FORCE is enabled, because there is nothing outstanding to sync).

Also fixed TestFilterFileSystem.
Not sure what's wrong with testTrash.

Also I could use guidance for:
* what types of tests should I add
* If I wanted to add a feature where optionally only the first DN in the replication chain does the fsync, how should a client convey that to the FS.create method (it does not make sense that add another CreateFlag).

                
> Support hsync in HDFS
> ---------------------
>
>                 Key: HDFS-744
>                 URL: https://issues.apache.org/jira/browse/HDFS-744
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: data-node, hdfs client
>            Reporter: Hairong Kuang
>            Assignee: Lars Hofhansl
>         Attachments: HDFS-744-trunk-v2.patch, HDFS-744-trunk-v3.patch, HDFS-744-trunk.patch, hdfs-744-v2.txt, hdfs-744-v3.txt, hdfs-744.txt
>
>
> HDFS-731 implements hsync by default as hflush. As descriibed in HADOOP-6313, the real expected semantics should be "flushes out to all replicas and all replicas have done posix fsync equivalent - ie the OS has flushed it to the disk device (but the disk may have it in its cache)." This jira aims to implement the expected behaviour.

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