Zephyr Guo created HBASE-13997:
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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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