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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-895) Allow hflush/sync to occur in parallel with new writes to the file
Date Sun, 14 Nov 2010 21:53:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-895?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12931901#action_12931901
] 

Hairong Kuang commented on HDFS-895:
------------------------------------

+1. This looks good to me except that the following unnecessary import.
 import org.apache.hadoop.hdfs.server.namenode.LeaseExpiredException;

Could you please post ant patch & test results?

> Allow hflush/sync to occur in parallel with new writes to the file
> ------------------------------------------------------------------
>
>                 Key: HDFS-895
>                 URL: https://issues.apache.org/jira/browse/HDFS-895
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs client
>    Affects Versions: 0.22.0
>            Reporter: dhruba borthakur
>            Assignee: Todd Lipcon
>             Fix For: 0.22.0
>
>         Attachments: 895-delta-for-review.txt, hdfs-895-0.20-append.txt, hdfs-895-20.txt,
hdfs-895-branch-20-append.txt, hdfs-895-ontopof-1497.txt, hdfs-895-review.txt, hdfs-895-trunk.txt,
hdfs-895.txt, hdfs-895.txt, hdfs-895.txt, hdfs-895.txt, hdfs-895.txt, hdfs-895.txt
>
>
> In the current trunk, the HDFS client methods writeChunk() and hflush./sync are syncronized.
This means that if a hflush/sync is in progress, an applicationn cannot write data to the
HDFS client buffer. This reduces the write throughput of the transaction log in HBase. 
> The hflush/sync should allow new writes to happen to the HDFS client even when a hflush/sync
is in progress. It can record the seqno of the message for which it should receice the ack,
indicate to the DataStream thread to star flushing those messages, exit the synchronized section
 and just wai for that ack to arrive.

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