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https://issues.apache.org/jira/browse/HDFS-14497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16852354#comment-16852354
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Hudson commented on HDFS-14497:
-------------------------------

SUCCESS: Integrated in Jenkins build Hadoop-trunk-Commit #16636 (See 
[https://builds.apache.org/job/Hadoop-trunk-Commit/16636/])
HDFS-14497. Write lock held by metasave impact following RPC processing. 
(weichiu: rev 33c62f8f4e94442825fe286c2b18518925d980e6)
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestMetaSave.java


> Write lock held by metasave impact following RPC processing
> -----------------------------------------------------------
>
>                 Key: HDFS-14497
>                 URL: https://issues.apache.org/jira/browse/HDFS-14497
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: He Xiaoqiao
>            Assignee: He Xiaoqiao
>            Priority: Major
>             Fix For: 3.3.0
>
>         Attachments: HDFS-14497.001.patch
>
>
> NameNode meta save hold global write lock currently, so following RPC r/w 
> request or inner-thread of NameNode could be paused if they try to acquire 
> global read/write lock and have to wait before metasave release it.
> I propose to change write lock to read lock and let some read request could 
> be process normally. I think it could not change informations which meta save 
> try to get if we try to open read request.
> Actually, we need ensure that there are only one thread to execute metaSave, 
> otherwise, output streams could meet exception especially both streams hold 
> the same file handle or some other same output stream.



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