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https://issues.apache.org/jira/browse/HBASE-7018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13480581#comment-13480581
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Gregory Chanan commented on HBASE-7018:
---------------------------------------
Benchmarks for trunk:
First test: Bulk assign 500 empty regions in one table on my local box. Run
each trial 3 times.
Without patch: 1.299 s
With patch: 1.194 s
Second test: Bulk assign 400 regions, all belonging to separate tables (so 400
tables). Same setup otherwise. This is really to test the RPC improvements.
Without patch: 3.338 s
With patch: 2.648 s
> Fix and Improve TableDescriptor caching for bulk assignment
> -----------------------------------------------------------
>
> Key: HBASE-7018
> URL: https://issues.apache.org/jira/browse/HBASE-7018
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: Gregory Chanan
> Assignee: Gregory Chanan
> Fix For: 0.94.3, 0.96.0
>
> Attachments: HBASE-7018-94.patch, HBASE-7018-94-v2.patch,
> HBASE-7018-trunk.patch
>
>
> HBASE-6214 backported HBASE-5998 (Bulk assignment: regionserver optimization
> by using a temporary cache for table descriptors when receiving an open
> regions request), but it's buggy on 0.94 (0.96 appears correct):
> {code}
> HTableDescriptor htd = null;
> if (htds == null) {
> htd = this.tableDescriptors.get(region.getTableName());
> } else {
> htd = htds.get(region.getTableNameAsString());
> if (htd == null) {
> htd = this.tableDescriptors.get(region.getTableName());
> htds.put(region.getRegionNameAsString(), htd);
> }
> }
> {code}
> i.e. we get the tableName from the map but write the regionName.
> Even fixing this, it looks like there are areas for improvement:
> 1) FSTableDescriptors already has a cache (though it goes to the NameNode
> each time through to check we have the latest copy. May as well combine
> these two caches, might be a performance win as well since we don't need to
> write to multiple caches.
> 2) FSTableDescriptors makes two RPCs to the NameNode when it encounters a new
> table. So the total number of RPCs necessary for a bulk assign (without
> caching is):
> #regions + #tables
> (with caching):
> min(#regions,#tables) + #tables = #tables + #tables = 2 * #tables
> We can make this only one RPC, yielding:
> #tables
> Probably not a big deal for most users, but in a multi-tenant situation where
> the number of regions being bulk assigned approaches the number of tables
> being bulk assigned, this could be a nice performance win.
> Benchmarks coming.
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