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From "Zephyr Guo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-13997) ScannerCallableWithReplicas cause Infinitely blocking
Date Tue, 30 Jun 2015 10:30:05 GMT
Zephyr Guo created HBASE-13997:
----------------------------------

             Summary: ScannerCallableWithReplicas cause Infinitely blocking
                 Key: HBASE-13997
                 URL: https://issues.apache.org/jira/browse/HBASE-13997
             Project: HBase
          Issue Type: Bug
          Components: Client
    Affects Versions: 1.0.1.1
            Reporter: Zephyr Guo
            Assignee: Zephyr Guo
            Priority: Minor


Bug in ScannerCallableWithReplicas.addCallsForOtherReplicas method  
{code:title=ScannerCallableWithReplicas.java|borderStyle=solid}
private int addCallsForOtherReplicas(
      BoundedCompletionService<Pair<Result[], ScannerCallable>> cs, RegionLocations
rl, int min,
      int max) {
    if (scan.getConsistency() == Consistency.STRONG) {
      return 0; // not scheduling on other replicas for strong consistency
    }
    for (int id = min; id <= max; id++) {
      if (currentScannerCallable.getHRegionInfo().getReplicaId() == id) {
        continue; //this was already scheduled earlier
      }
      ScannerCallable s = currentScannerCallable.getScannerCallableForReplica(id);
      if (this.lastResult != null) {
        s.getScan().setStartRow(this.lastResult.getRow());
      }
      outstandingCallables.add(s);
      RetryingRPC retryingOnReplica = new RetryingRPC(s);
      cs.submit(retryingOnReplica);
    }
    return max - min + 1;	//bug? max - min
  }
{code}
It can cause completed < submitted always so that the following code will be infinitely
blocked.
{code:title=ScannerCallableWithReplicas.java|borderStyle=solid}
 while (completed < submitted) {
        try {
          Future<Pair<Result[], ScannerCallable>> f = cs.take();
          Pair<Result[], ScannerCallable> r = f.get();
          if (r != null && r.getSecond() != null) {
            updateCurrentlyServingReplica(r.getSecond(), r.getFirst(), done, pool);
          }
          return r == null ? null : r.getFirst(); // great we got an answer
        } catch (ExecutionException e) {
          // if not cancel or interrupt, wait until all RPC's are done
          // one of the tasks failed. Save the exception for later.
          if (exceptions == null) exceptions = new ArrayList<ExecutionException>(rl.size());
          exceptions.add(e);
          completed++;
        }
      }
{code}
The code in ScannerCallableWithReplicas.call

If all replica-RS occur ExecutionException ,it will be blocked in  cs.take()




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