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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8806) Row locks are acquired repeatedly in HRegion.doMiniBatchMutation for duplicate rows.
Date Wed, 03 Jul 2013 22:26:21 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13699530#comment-13699530
] 

Lars Hofhansl commented on HBASE-8806:
--------------------------------------

Specifically, for 0.94 I'd prefer the fix with the row cache (the first two patches). In order
to reduce the performance impact we can probably pass HashedBytes to getLock directly, instead
of creating them in doMiniBatchMutation(...) and then again in internalObtainRowLock(...).

For 0.96 Dave's patch is nice. For that patch, we could even invent "lock groups", simply
by passing a grouping object to {get|try}RowLock and releaseMyRowLocks. To group by thread
we'd pass in the currentThread object; and we could also group only for this batch, by passing
batchOp as group object.

                
> Row locks are acquired repeatedly in HRegion.doMiniBatchMutation for duplicate rows.
> ------------------------------------------------------------------------------------
>
>                 Key: HBASE-8806
>                 URL: https://issues.apache.org/jira/browse/HBASE-8806
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.94.5
>            Reporter: rahul gidwani
>            Priority: Critical
>             Fix For: 0.95.2, 0.94.10
>
>         Attachments: HBASE-8806-0.94.10.patch, HBASE-8806-0.94.10-v2.patch, HBASE-8806.patch,
HBASE-8806-threadBasedRowLocks.patch
>
>
> If we already have the lock in the doMiniBatchMutation we don't need to re-acquire it.
The solution would be to keep a cache of the rowKeys already locked for a miniBatchMutation
and If we already have the 
> rowKey in the cache, we don't repeatedly try and acquire the lock.  A fix to this problem
would be to keep a set of rows we already locked and not try to acquire the lock for these
rows.  
> We have tested this fix in our production environment and has improved replication performance
quite a bit.  We saw a replication batch go from 3+ minutes to less than 10 seconds for batches
with duplicate row keys.
> {code}
> static final int ACQUIRE_LOCK_COUNT = 0;
>   @Test
>   public void testRedundantRowKeys() throws Exception {
>     final int batchSize = 100000;
>     
>     String tableName = getClass().getSimpleName();
>     Configuration conf = HBaseConfiguration.create();
>     conf.setClass(HConstants.REGION_IMPL, MockHRegion.class, HeapSize.class);
>     MockHRegion region = (MockHRegion) TestHRegion.initHRegion(Bytes.toBytes(tableName),
tableName, conf, Bytes.toBytes("a"));
>     List<Pair<Mutation, Integer>> someBatch = Lists.newArrayList();
>     int i = 0;
>     while (i < batchSize) {
>       if (i % 2 == 0) {
>         someBatch.add(new Pair<Mutation, Integer>(new Put(Bytes.toBytes(0)), null));
>       } else {
>         someBatch.add(new Pair<Mutation, Integer>(new Put(Bytes.toBytes(1)), null));
>       }
>       i++;
>     }
>     long startTime = System.currentTimeMillis();
>     region.batchMutate(someBatch.toArray(new Pair[0]));
>     long endTime = System.currentTimeMillis();
>     long duration = endTime - startTime;
>     System.out.println("duration: " + duration + " ms");
>     assertEquals(2, ACQUIRE_LOCK_COUNT);
>   }
>   @Override
>   public Integer getLock(Integer lockid, byte[] row, boolean waitForLock) throws IOException
{
>     ACQUIRE_LOCK_COUNT++;
>     return super.getLock(lockid, row, waitForLock);
>   }
> {code}

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