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HBase Review Board commented on HBASE-2468: ------------------------------------------- Message from: "Mingjie Lai" <mjla...@gmail.com> ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: http://review.hbase.org/r/98/ ----------------------------------------------------------- (Updated 2010-06-09 15:50:59.084657) Review request for hbase, Todd Lipcon and stack. Changes ------- @St^ack: please see my comments for your feedback regarding getRowOrBefore() issue. Invite Todd as a reviewer. Summary ------- HBASE-2468: Improvements to prewarm META cache on clients. Changes: 1. Add new HTable methods which support region info de/serialation, and region cache prewarm: - void serializeRegionInfo(): clients could perform a large scan for all the meta for the table, serialize the meta to a file. MR job can ship a copy of the meta for the table in the DistributedCache - Map<HRegionInfo, HServerAddress> deserializeRegionInfo(): MR job can deserialize the region info from the DistributedCache - prewarmRegionCache(Map<HRegionInfo, HServerAddress> regionMap): MR job can prewarm local region cache by the deserialized region info. 2. For each client, each region cache read-miss could trigger read-ahead some number of rows in META. This option could be turned on and off for one particular table. This addresses bug HBASE-2468. http://issues.apache.org/jira/browse/HBASE-2468 Diffs ----- src/main/java/org/apache/hadoop/hbase/client/HConnection.java 853164d src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java ed18092 src/main/java/org/apache/hadoop/hbase/client/HTable.java 7ec95cb src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java d3a0c07 src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide.java 95e494a Diff: http://review.hbase.org/r/98/diff Testing ------- Unit tests passed locally for me. Thanks, Mingjie > Improvements to prewarm META cache on clients > --------------------------------------------- > > Key: HBASE-2468 > URL: https://issues.apache.org/jira/browse/HBASE-2468 > Project: HBase > Issue Type: Improvement > Components: client > Reporter: Todd Lipcon > Assignee: Mingjie Lai > Fix For: 0.21.0 > > Attachments: HBASE-2468-trunk.patch > > > A couple different use cases cause storms of reads to META during startup. > For example, a large MR job will cause each map task to hit meta since it > starts with an empty cache. > A couple possible improvements have been proposed: > - MR jobs could ship a copy of META for the table in the DistributedCache > - Clients could prewarm cache by doing a large scan of all the meta for the > table instead of random reads for each miss > - Each miss could fetch ahead some number of rows in META -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.