cuijianwei created HBASE-11623:
----------------------------------

             Summary: mutateRowsWithLocks might require updatesLock.readLock 
with waitTime=0
                 Key: HBASE-11623
                 URL: https://issues.apache.org/jira/browse/HBASE-11623
             Project: HBase
          Issue Type: Improvement
          Components: regionserver
    Affects Versions: 0.98.4, 0.94.21, 0.96.1.1
            Reporter: cuijianwei
            Priority: Minor


mutateRowsWithLocks will acquire updatesLock.readLock by the following code:
{code}
...
lock(this.updatesLock.readLock(), acquiredRowLocks.size());
...
{code}
However, acquiredRowLocks might be empty, and then the waitTime of 
HRegion.lock(...) will be set to 0, which will make mutateRowsWithLocks fail if 
can not acquire updatesLock.readLock immediately. 
In our environment, we implement a region coprocessor which need to hold row 
locks before invoke mutateRowsWithLocks. Then, the rowsToLock(passed to 
mutateRowsWithLocks) will be an empty set, and we get the following exception 
occasionally:
{code}
org.apache.hadoop.hbase.RegionTooBusyException: failed to get a lock in 0ms     
                                                                                
             
 582   at org.apache.hadoop.hbase.regionserver.HRegion.lock(HRegion.java:6191)
 583   at 
org.apache.hadoop.hbase.regionserver.HRegion.mutateRowsWithLocks(HRegion.java:5126)
 584   at 
org.apache.hadoop.hbase.regionserver.HRegion.mutateRowsWithLocks(HRegion.java:5034)
...
{code} 
Is it reasonable that we use default waitTime when rowsToLock is empty? (as the 
following code)
{code}
lock(this.updatesLock.readLock(), acquiredRowLocks.size() == 0 ? 1 : 
acquiredRowLocks.size() );
{code}



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