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https://issues.apache.org/jira/browse/HDFS-14497?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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He Xiaoqiao updated HDFS-14497:
-------------------------------
    Attachment: HDFS-14497-addendum.001.patch

> 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-addendum.001.patch, 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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