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https://issues.apache.org/jira/browse/HBASE-5877?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267879#comment-13267879
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Zhihong Yu commented on HBASE-5877:
-----------------------------------

{code}
+        final Set<String> updateHistory = new HashSet<String>(100);
{code}
Since updateCachedLocations() is used to handle exception, the presizing above 
may not be needed.
{code}
+    this(server, rsServices, regionInfo, abort, zk, versionOfClosingNode, 
eventType, null);
+  }
+
+    protected CloseRegionHandler(final Server server,
{code}
The indentation of CloseRegionHandler() above is off.
{code}
+  // This map will contains all the regions that we closed for a move.
+  //  We add the time it was moved as we don't want to keep a too old 
information
{code}
'will contains' -> 'will contain'. 'keep a too old' -> 'keep too old'.

This is a very useful feature. Good work, N.
                
> When a query fails because the region has moved, let the regionserver return 
> the new address to the client
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5877
>                 URL: https://issues.apache.org/jira/browse/HBASE-5877
>             Project: HBase
>          Issue Type: Improvement
>          Components: client, master, regionserver
>    Affects Versions: 0.96.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>             Fix For: 0.96.0
>
>         Attachments: 5877.v1.patch, 5877.v12.patch, 5877.v6.patch
>
>
> This is mainly useful when we do a rolling restart. This will decrease the 
> load on the master and the network load.
> Note that a region is not immediately opened after a close. So:
> - it seems preferable to wait before retrying on the other server. An 
> optimisation would be to have an heuristic depending on when the region was 
> closed.
> - during a rolling restart, the server moves the regions then stops. So we 
> may have failures when the server is stopped, and this patch won't help.
> The implementation in the first patch does:
> - on the region move, there is an added parameter on the regionserver#close 
> to say where we are sending the region
> - the regionserver keeps a list of what was moved. Each entry is kept 100 
> seconds.
> - the regionserver sends a specific exception when it receives a query on a 
> moved region. This exception contains the new address.
> - the client analyses the exeptions and update its cache accordingly...

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