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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8806) Row locks are acquired repeatedly in HRegion.doMiniBatchMutation for duplicate rows.
Date Thu, 04 Jul 2013 10:47:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13699990#comment-13699990
] 

Anoop Sam John commented on HBASE-8806:
---------------------------------------

For the normal case there will be always a rowsAlreadyLocked.contains(currentRow) check for
every row.
One way which could favor this normal case is have this check after 
acquiredLockId = getLock(providedLockId, currentRow, shouldBlock);
iff acquiredLockId == null
Well there is no problem in calling getLock before the new contains check as shouldBlock will
be false except for the 1st time. When shouldBlock is false it will immediately return with
null. Also for the 1st time any way rowsAlreadyLocked will be empty too.

In this, the case where the duplicate entries are there in batch, will have to do some extra
ops in getLock.

Just saying. what do you say Lars?

                
> 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: 8806-0.94-v4.txt, 8806-0.94-v5.txt, HBASE-8806-0.94.10.patch, HBASE-8806-0.94.10-v2.patch,
HBASE-8806-0.94.10-v3.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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