[jira] [Created] (HBASE-17361) HTable#getBufferedMutator is not thread safe and could get data loss

["Yu Li (JIRA)" <ji...@apache.org>]

Yu Li created HBASE-17361:
-----------------------------

             Summary: HTable#getBufferedMutator is not thread safe and could get data loss
                 Key: HBASE-17361
                 URL: https://issues.apache.org/jira/browse/HBASE-17361
             Project: HBase
          Issue Type: Bug
            Reporter: Yu Li
            Assignee: Yu Li
            Priority: Critical


Now we have {{HTable#getBufferedMutator}} like
{code}
   BufferedMutator getBufferedMutator() throws IOException {
     if (mutator == null) {
      this.mutator = (BufferedMutatorImpl) connection.getBufferedMutator(
          new BufferedMutatorParams(tableName)
              .pool(pool)
              .writeBufferSize(connConfiguration.getWriteBufferSize())
              .maxKeyValueSize(connConfiguration.getMaxKeyValueSize())
      );
    }
    mutator.setRpcTimeout(writeRpcTimeout);
    mutator.setOperationTimeout(operationTimeout);
    return mutator;
  }
{code}
And {{HTable#flushCommits}}:
{code}
  void flushCommits() throws IOException {
    if (mutator == null) {
      // nothing to flush if there's no mutator; don't bother creating one.
      return;
    }
    getBufferedMutator().flush();
  }
{code}
For {{HTable#put}}
{code}
  public void put(final Put put) throws IOException {
    getBufferedMutator().mutate(put);
    flushCommits();
  }
{code}
If we launch multiple threads to put in parallel, below sequence might happen because {{HTable#getBufferedMutator}} is not thread safe:
{noformat}
1. ThreadA runs to getBufferedMutator and finds mutator==null
2. ThreadB runs to getBufferedMutator and finds mutator==null
3. ThreadA initialize mutator to instanceA, then calls mutator#mutate,
adding one put (putA) into {{writeAsyncBuffer}}
4. ThreadB initialize mutator to instanceB
5. ThreadA runs to flushCommits, now mutator is instanceB, it calls
instanceB's flush method, putA is lost
{noformat}

Will add a UT to cover this case, and fix it in this JIRA.



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