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https://issues.apache.org/jira/browse/HBASE-21065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17018270#comment-17018270
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Michael Stack commented on HBASE-21065:
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Changing the encoding on meta exposes the fact that the ROW_INDEX_V1 encoder
does not work on the hbase:meta table; it has hard-coded the user-space
CellComparator. Reviewing how CellComparators are instantiated around the
codebase, we are inconsistent and encoding context does not have what
CellComparator is appropriate. Let me fix this first. Will fix the UT failures
we're seeing in the PR here.
> Try ROW_INDEX_V1 encoding on meta table (fix bloomfilters on meta while we
> are at it)
> -------------------------------------------------------------------------------------
>
> Key: HBASE-21065
> URL: https://issues.apache.org/jira/browse/HBASE-21065
> Project: HBase
> Issue Type: Improvement
> Components: meta, Performance
> Reporter: Michael Stack
> Assignee: Michael Stack
> Priority: Major
>
> Some users end up hitting meta hard. Bulk is probably because our client goes
> to meta too often, and the real 'fix' for a saturated meta is splitting it,
> but the encoding that came in with HBASE-16213, ROW_INDEX_V1, could help in
> the near term. It adds an index on hfile blocks and helped improve random
> reads against user-space tables (less compares as we used index to go direct
> to requested Cells rather than look at each Cell in turn until we found what
> we wanted -- see RN on HBASE-16213 for citation).
> I also noticed code-reading that we don't enable blooms on hbase:meta tables;
> that could save some CPU and speed things up a bit too:
> {code}
> // Disable blooms for meta. Needs work. Seems to mess w/
> getClosestOrBefore.
> .setBloomFilterType(BloomType.NONE)
> {code}
> This issue is about doing a bit of perf compare of encoding *on* vs current
> default (and will check diff in size of indexed blocks).
> Meta access is mostly random-read I believe (A review of a user's access
> showed this so at least for their workload). The nice addition, HBASE-19722
> Meta query statistics metrics source, would help verify if it saw some usage
> on a prod cluster.
> If all is good, I'd like to make a small patch, one that could be easily
> backported, with minimal changes in it.
> As is, its all a little awkward as the meta table schema is hard-coded and
> meta is immutable -- stuff we'll have to fix if we want to split meta -- so
> in the meantime it requires a code change to enable (and a backport of
> HBASE-16213 -- this patch is in 1.4.0 only currently, perhaps that is
> enough). Code change to enable is small:
> {code}
> diff --git
> a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
>
> b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
> index 28c7ec3c2f..8f08f94dc1 100644
> ---
> a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
> +++
> b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
> @@ -160,6 +160,7 @@ public class FSTableDescriptors implements
> TableDescriptors {
> .setScope(HConstants.REPLICATION_SCOPE_LOCAL)
> // Disable blooms for meta. Needs work. Seems to mess w/
> getClosestOrBefore.
> .setBloomFilterType(BloomType.NONE)
> +
> .setDataBlockEncoding(org.apache.hadoop.hbase.io.encoding.DataBlockEncoding.ROW_INDEX_V1)
> .build())
>
> .setColumnFamily(ColumnFamilyDescriptorBuilder.newBuilder(HConstants.TABLE_FAMILY)
> .setMaxVersions(conf.getInt(HConstants.HBASE_META_VERSIONS,
> {code}
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