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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8369) MapReduce over snapshot files
Date Sun, 15 Dec 2013 02:03:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13848504#comment-13848504
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Lars Hofhansl commented on HBASE-8369:
--------------------------------------

These seems inmportant:
bq. TableMapreduceUtil changes (other than the new method): needed in case security is enabled.
We should not talk with the HBase cluster at all.
bq. HDFSBlocksDistribution: in v3, we are providing 3 servers with highest locality to the
input split. In v11, we are using all the servers with 80% of the locality for the top locality
server. This ensures better locality.

This seems nice to have: 
bq. ClientScanner / AbstractClientScanner / TableRecordReaderImpl changes: the ClientSideRegion
scanner keeps track of ScanMetrics, and exports those via MR job counters or Scan.

To track what/how the mappers are doing.
The rest we can do without in 0.94. Let's also move the discussion to HBASE-10076.

> 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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