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From "Phabricator (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5259) Normalize the RegionLocation in TableInputFormat by the reverse DNS lookup.
Date Fri, 27 Jan 2012 05:35:47 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13194482#comment-13194482
] 

Phabricator commented on HBASE-5259:
------------------------------------

Kannan has accepted the revision "[jira][HBASE-5259] Normalize the RegionLocation in TableInputFormat
by the reverse DNS lookup.".

  Liyin -- looks good to me. One minor suggestion inlined.

INLINE COMMENTS
  src/main/java/org/apache/hadoop/hbase/mapreduce/TableInputFormatBase.java:171 logging here
is unnecessary because of logging in line 191. The "split" (TableSplit's toString() method
already will print the regionLocation along with the start/stop keys for each map task.

REVISION DETAIL
  https://reviews.facebook.net/D1413

                
> Normalize the RegionLocation in TableInputFormat by the reverse DNS lookup.
> ---------------------------------------------------------------------------
>
>                 Key: HBASE-5259
>                 URL: https://issues.apache.org/jira/browse/HBASE-5259
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Liyin Tang
>            Assignee: Liyin Tang
>         Attachments: D1413.1.patch, D1413.1.patch, D1413.1.patch, D1413.1.patch, D1413.2.patch,
D1413.2.patch, D1413.2.patch, D1413.2.patch, D1413.3.patch, D1413.3.patch, D1413.3.patch,
D1413.3.patch
>
>
> Assuming the HBase and MapReduce running in the same cluster, the TableInputFormat is
to override the split function which divides all the regions from one particular table into
a series of mapper tasks. So each mapper task can process a region or one part of a region.
Ideally, the mapper task should run on the same machine on which the region server hosts the
corresponding region. That's the motivation that the TableInputFormat sets the RegionLocation
so that the MapReduce framework can respect the node locality. 
> The code simply set the host name of the region server as the HRegionLocation. However,
the host name of the region server may have different format with the host name of the task
tracker (Mapper task). The task tracker always gets its hostname by the reverse DNS lookup.
And the DNS service may return different host name format. For example, the host name of the
region server is correctly set as a.b.c.d while the reverse DNS lookup may return a.b.c.d.
(With an additional doc in the end).
> So the solution is to set the RegionLocation by the reverse DNS lookup as well. No matter
what host name format the DNS system is using, the TableInputFormat has the responsibility
to keep the consistent host name format with the MapReduce framework.

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