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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8369) MapReduce over snapshot files
Date Thu, 29 May 2014 19:03:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14012727#comment-14012727
] 

Enis Soztutar commented on HBASE-8369:
--------------------------------------

bq. I think the restoreDir here will be the root directory of the restored snapshot and hence
the conf.set should not set restoreDir as the tableDir, rather it should be doing the following
We are restoring the snapshot to the restoreDir, which would create the sym-link files for
the table. We are setting the table dir to the restore directory, so that we can open the
table's regions from the restore directory. We cannot use the root directory since that would
mean we are reading from the actual table's regions rather than snapshot's regions. 
Did you run into a problem with this patch? Why do you think this is a problem? 

> MapReduce over snapshot files
> -----------------------------
>
>                 Key: HBASE-8369
>                 URL: https://issues.apache.org/jira/browse/HBASE-8369
>             Project: HBase
>          Issue Type: New Feature
>          Components: mapreduce, snapshots
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.0
>
>         Attachments: HBASE-8369-0.94.patch, HBASE-8369-0.94_v2.patch, HBASE-8369-0.94_v3.patch,
HBASE-8369-0.94_v4.patch, HBASE-8369-0.94_v5.patch, HBASE-8369-trunk_v1.patch, HBASE-8369-trunk_v2.patch,
HBASE-8369-trunk_v3.patch, hbase-8369_v0.patch, hbase-8369_v11.patch, hbase-8369_v5.patch,
hbase-8369_v6.patch, hbase-8369_v7.patch, hbase-8369_v8.patch, hbase-8369_v9.patch
>
>
> The idea is to add an InputFormat, which can run the mapreduce job over snapshot files
directly bypassing hbase server layer. The IF is similar in usage to TableInputFormat, taking
a Scan object from the user, but instead of running from an online table, it runs from a table
snapshot. We do one split per region in the snapshot, and open an HRegion inside the RecordReader.
A RegionScanner is used internally for doing the scan without any HRegionServer bits. 
> Users have been asking and searching for ways to run MR jobs by reading directly from
hfiles, so this allows new use cases if reading from stale data is ok:
>  - Take snapshots periodically, and run MR jobs only on snapshots.
>  - Export snapshots to remote hdfs cluster, run the MR jobs at that cluster without HBase
cluster.
>  - (Future use case) Combine snapshot data with online hbase data: Scan from yesterday's
snapshot, but read today's data from online hbase cluster. 



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