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From "jiraposter@reviews.apache.org (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-2600) Change how we do meta tables; from tablename+STARTROW+randomid to instead, tablename+ENDROW+randomid
Date Tue, 17 Jan 2012 01:19:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13187359#comment-13187359
] 

jiraposter@reviews.apache.org commented on HBASE-2600:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/3466/
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(Updated 2012-01-17 01:17:10.937632)


Review request for hbase and Michael Stack.


Summary
-------

This is an idea that Ryan and I have been kicking around on and off for a while now.

If regionnames were made of tablename+endrow instead of tablename+startrow, then in the metatables,
doing a search for the region that contains the wanted row, we'd just have to open a scanner
using passed row and the first row found by the scan would be that of the region we need (If
offlined parent, we'd have to scan to the next row).

If we redid the meta tables in this format, we'd be using an access that is natural to hbase,
a scan as opposed to the perverse, expensive getClosestRowBefore we currently have that has
to walk backward in meta finding a containing region.

This issue is about changing the way we name regions.

If we were using scans, prewarming client cache would be near costless (as opposed to what
we'll currently have to do which is first a getClosestRowBefore and then a scan from the closestrowbefore
forward).

Converting to the new method, we'd have to run a migration on startup changing the content
in meta.

Up to this, the randomid component of a region name has been the timestamp of region creation.
HBASE-2531 "32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash clashes"
proposes changing the randomid so that it contains actual name of the directory in the filesystem
that hosts the region. If we had this in place, I think it would help with the migration to
this new way of doing the meta because as is, the region name in fs is a hash of regionname...
changing the format of the regionname would mean we generate a different hash... so we'd need
hbase-2531 to be in place before we could do this change.


This addresses bug HBASE-2600.
    https://issues.apache.org/jira/browse/HBASE-2600


Diffs (updated)
-----

  src/main/java/org/apache/hadoop/hbase/HConstants.java 904e2d2 
  src/main/java/org/apache/hadoop/hbase/HRegionInfo.java 74cb821 
  src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java 133759d 
  src/main/java/org/apache/hadoop/hbase/KeyValue.java be7e2d8 
  src/main/java/org/apache/hadoop/hbase/catalog/MetaReader.java e5e60a8 
  src/main/java/org/apache/hadoop/hbase/client/HBaseAdmin.java 88c381f 
  src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java 99f90b2 
  src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java f0c6828 
  src/main/java/org/apache/hadoop/hbase/master/handler/ServerShutdownHandler.java 8f4f4b8

  src/main/java/org/apache/hadoop/hbase/rest/RegionsResource.java bf85bc1 
  src/main/java/org/apache/hadoop/hbase/rest/model/TableRegionModel.java 67e7a04 
  src/test/java/org/apache/hadoop/hbase/TestKeyValue.java dc4ee8d 
  src/test/java/org/apache/hadoop/hbase/regionserver/TestGetClosestAtOrBefore.java 5f97167

  src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegionInfo.java 6e1211b 
  src/test/java/org/apache/hadoop/hbase/rest/TestStatusResource.java cffdcb6 
  src/test/java/org/apache/hadoop/hbase/rest/model/TestTableRegionModel.java b6f0ab5 

Diff: https://reviews.apache.org/r/3466/diff


Testing
-------

Unit tests started table. 


Tests in error: 
  org.apache.hadoop.hbase.client.TestMetaMigrationRemovingHTD: Table 'TestTable we searched
for the StartKey: TestTable ,, startKey lastChar's int value: 32 with the stopKey: TestTable#,,
stopRow lastChar's int value: 35 with parentTable:.META.

I need to know how to update/recreate the tar ball which is the source for that test.


Thanks,

Alex


                
> Change how we do meta tables; from tablename+STARTROW+randomid to instead, tablename+ENDROW+randomid
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-2600
>                 URL: https://issues.apache.org/jira/browse/HBASE-2600
>             Project: HBase
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: Alex Newman
>         Attachments: 0001-Changed-regioninfo-format-to-use-endKey-instead-of-s.patch,
0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v2.patch, 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen.patch
>
>
> This is an idea that Ryan and I have been kicking around on and off for a while now.
> If regionnames were made of tablename+endrow instead of tablename+startrow, then in the
metatables, doing a search for the region that contains the wanted row, we'd just have to
open a scanner using passed row and the first row found by the scan would be that of the region
we need (If offlined parent, we'd have to scan to the next row).
> If we redid the meta tables in this format, we'd be using an access that is natural to
hbase, a scan as opposed to the perverse, expensive getClosestRowBefore we currently have
that has to walk backward in meta finding a containing region.
> This issue is about changing the way we name regions.
> If we were using scans, prewarming client cache would be near costless (as opposed to
what we'll currently have to do which is first a getClosestRowBefore and then a scan from
the closestrowbefore forward).
> Converting to the new method, we'd have to run a migration on startup changing the content
in meta.
> Up to this, the randomid component of a region name has been the timestamp of region
creation.   HBASE-2531 "32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash
clashes" proposes changing the randomid so that it contains actual name of the directory in
the filesystem that hosts the region.  If we had this in place, I think it would help with
the migration to this new way of doing the meta because as is, the region name in fs is a
hash of regionname... changing the format of the regionname would mean we generate a different
hash... so we'd need hbase-2531 to be in place before we could do this change.

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