/**
* Algo: - we put the query into the execution pool. - after x ms, if we don't have a result, we
* add the queries for the secondary replicas - we take the first answer - when done, we cancel
* what's left. Cancelling means: - removing from the pool if the actual call was not started -
* interrupting the call if it has started Client side, we need to take into account - a call is
* not executed immediately after being put into the pool - a call is a thread. Let's not multiply
* the number of thread by the number of replicas. Server side, if we can cancel when it's still
* in the handler pool, it's much better, as a call can take some i/o.
*
* <p>Globally, the number of retries, timeout and so on still applies, but it's per replica, not
* global. We continue until all retries are done, or all timeouts are exceeded.
*/
public synchronized Result call()
throws DoNotRetryIOException, InterruptedIOException, RetriesExhaustedException {
boolean isTargetReplicaSpecified = (get.getReplicaId() >= 0);
RegionLocations rl =
getRegionLocations(
true,
(isTargetReplicaSpecified ? get.getReplicaId() : RegionReplicaUtil.DEFAULT_REPLICA_ID),
cConnection,
tableName,
get.getRow());
ResultBoundedCompletionService<Result> cs =
new ResultBoundedCompletionService<Result>(this.rpcRetryingCallerFactory, pool, rl.size());
if (isTargetReplicaSpecified) {
addCallsForReplica(cs, rl, get.getReplicaId(), get.getReplicaId());
} else {
addCallsForReplica(cs, rl, 0, 0);
try {
// wait for the timeout to see whether the primary responds back
Future<Result> f = cs.poll(timeBeforeReplicas, TimeUnit.MICROSECONDS); // Yes, microseconds
if (f != null) {
return f.get(); // great we got a response
}
} catch (ExecutionException e) {
throwEnrichedException(e, retries);
} catch (CancellationException e) {
throw new InterruptedIOException();
} catch (InterruptedException e) {
throw new InterruptedIOException();
}
// submit call for the all of the secondaries at once
addCallsForReplica(cs, rl, 1, rl.size() - 1);
}
try {
try {
Future<Result> f = cs.take();
return f.get();
} catch (ExecutionException e) {
throwEnrichedException(e, retries);
}
} catch (CancellationException e) {
throw new InterruptedIOException();
} catch (InterruptedException e) {
throw new InterruptedIOException();
} finally {
// We get there because we were interrupted or because one or more of the
// calls succeeded or failed. In all case, we stop all our tasks.
cs.cancelAll();
}
return null; // unreachable
}
/**
* Creates the calls and submit them
*
* @param cs - the completion service to use for submitting
* @param rl - the region locations
* @param min - the id of the first replica, inclusive
* @param max - the id of the last replica, inclusive.
*/
private void addCallsForReplica(
ResultBoundedCompletionService<Result> cs, RegionLocations rl, int min, int max) {
for (int id = min; id <= max; id++) {
HRegionLocation hrl = rl.getRegionLocation(id);
ReplicaRegionServerCallable callOnReplica = new ReplicaRegionServerCallable(id, hrl);
cs.submit(callOnReplica, callTimeout, id);
}
}
private void printLocations(Result r) {
RegionLocations rl = null;
if (r == null) {
LOG.info("FAILED FOR null Result");
return;
}
LOG.info("FAILED FOR " + resultToString(r) + " Stale " + r.isStale());
if (r.getRow() == null) {
return;
}
try {
rl = ((ClusterConnection) connection).locateRegion(tableName, r.getRow(), true, true);
} catch (IOException e) {
LOG.warn("Couldn't get locations for row " + Bytes.toString(r.getRow()));
}
HRegionLocation locations[] = rl.getRegionLocations();
for (HRegionLocation h : locations) {
LOG.info("LOCATION " + h);
}
}
/**
* Two responsibilities - if the call is already completed (by another replica) stops the
* retries. - set the location to the right region, depending on the replica.
*/
@Override
public void prepare(final boolean reload) throws IOException {
if (controller.isCanceled()) return;
if (Thread.interrupted()) {
throw new InterruptedIOException();
}
if (reload || location == null) {
RegionLocations rl = getRegionLocations(false, id, cConnection, tableName, get.getRow());
location = id < rl.size() ? rl.getRegionLocation(id) : null;
}
if (location == null || location.getServerName() == null) {
// With this exception, there will be a retry. The location can be null for a replica
// when the table is created or after a split.
throw new HBaseIOException("There is no location for replica id #" + id);
}
ServerName dest = location.getServerName();
setStub(cConnection.getClient(dest));
}
@Override
public Result[] call(int timeout) throws IOException {
// If the active replica callable was closed somewhere, invoke the RPC to
// really close it. In the case of regular scanners, this applies. We make couple
// of RPCs to a RegionServer, and when that region is exhausted, we set
// the closed flag. Then an RPC is required to actually close the scanner.
if (currentScannerCallable != null && currentScannerCallable.closed) {
// For closing we target that exact scanner (and not do replica fallback like in
// the case of normal reads)
if (LOG.isDebugEnabled()) {
LOG.debug("Closing scanner " + currentScannerCallable.scannerId);
}
Result[] r = currentScannerCallable.call(timeout);
currentScannerCallable = null;
return r;
}
// We need to do the following:
// 1. When a scan goes out to a certain replica (default or not), we need to
// continue to hit that until there is a failure. So store the last successfully invoked
// replica
// 2. We should close the "losing" scanners (scanners other than the ones we hear back
// from first)
//
RegionLocations rl =
RpcRetryingCallerWithReadReplicas.getRegionLocations(
true,
RegionReplicaUtil.DEFAULT_REPLICA_ID,
cConnection,
tableName,
currentScannerCallable.getRow());
// allocate a boundedcompletion pool of some multiple of number of replicas.
// We want to accomodate some RPCs for redundant replica scans (but are still in progress)
BoundedCompletionService<Pair<Result[], ScannerCallable>> cs =
new BoundedCompletionService<Pair<Result[], ScannerCallable>>(pool, rl.size() * 5);
List<ExecutionException> exceptions = null;
int submitted = 0, completed = 0;
AtomicBoolean done = new AtomicBoolean(false);
replicaSwitched.set(false);
// submit call for the primary replica.
submitted += addCallsForCurrentReplica(cs, rl);
try {
// wait for the timeout to see whether the primary responds back
Future<Pair<Result[], ScannerCallable>> f =
cs.poll(timeBeforeReplicas, TimeUnit.MICROSECONDS); // Yes, microseconds
if (f != null) {
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 a response
}
} catch (ExecutionException e) {
// the primary call failed with RetriesExhaustedException or DoNotRetryIOException
// but the secondaries might still succeed. Continue on the replica RPCs.
exceptions = new ArrayList<ExecutionException>(rl.size());
exceptions.add(e);
completed++;
} catch (CancellationException e) {
throw new InterruptedIOException(e.getMessage());
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
}
// submit call for the all of the secondaries at once
// TODO: this may be an overkill for large region replication
submitted += addCallsForOtherReplicas(cs, rl, 0, rl.size() - 1);
try {
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++;
}
}
} catch (CancellationException e) {
throw new InterruptedIOException(e.getMessage());
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
} finally {
// We get there because we were interrupted or because one or more of the
// calls succeeded or failed. In all case, we stop all our tasks.
cs.cancelAll(true);
}
if (exceptions != null && !exceptions.isEmpty()) {
RpcRetryingCallerWithReadReplicas.throwEnrichedException(
exceptions.get(0), retries); // just rethrow the first exception for now.
}
return null; // unreachable
}
public void append(
TableName tableName, byte[] encodedRegionName, byte[] row, List<Entry> entries)
throws IOException {
if (disabledAndDroppedTables.getIfPresent(tableName) != null) {
if (LOG.isTraceEnabled()) {
LOG.trace(
"Skipping "
+ entries.size()
+ " entries because table "
+ tableName
+ " is cached as a disabled or dropped table");
for (Entry entry : entries) {
LOG.trace("Skipping : " + entry);
}
}
sink.getSkippedEditsCounter().addAndGet(entries.size());
return;
}
// If the table is disabled or dropped, we should not replay the entries, and we can skip
// replaying them. However, we might not know whether the table is disabled until we
// invalidate the cache and check from meta
RegionLocations locations = null;
boolean useCache = true;
while (true) {
// get the replicas of the primary region
try {
locations =
RegionReplicaReplayCallable.getRegionLocations(
connection, tableName, row, useCache, 0);
if (locations == null) {
throw new HBaseIOException(
"Cannot locate locations for " + tableName + ", row:" + Bytes.toStringBinary(row));
}
} catch (TableNotFoundException e) {
if (LOG.isTraceEnabled()) {
LOG.trace(
"Skipping "
+ entries.size()
+ " entries because table "
+ tableName
+ " is dropped. Adding table to cache.");
for (Entry entry : entries) {
LOG.trace("Skipping : " + entry);
}
}
disabledAndDroppedTables.put(tableName, Boolean.TRUE); // put to cache. Value ignored
// skip this entry
sink.getSkippedEditsCounter().addAndGet(entries.size());
return;
}
// check whether we should still replay this entry. If the regions are changed, or the
// entry is not coming from the primary region, filter it out.
HRegionLocation primaryLocation = locations.getDefaultRegionLocation();
if (!Bytes.equals(
primaryLocation.getRegionInfo().getEncodedNameAsBytes(), encodedRegionName)) {
if (useCache) {
useCache = false;
continue; // this will retry location lookup
}
if (LOG.isTraceEnabled()) {
LOG.trace(
"Skipping "
+ entries.size()
+ " entries in table "
+ tableName
+ " because located region "
+ primaryLocation.getRegionInfo().getEncodedName()
+ " is different than the original region "
+ Bytes.toStringBinary(encodedRegionName)
+ " from WALEdit");
for (Entry entry : entries) {
LOG.trace("Skipping : " + entry);
}
}
sink.getSkippedEditsCounter().addAndGet(entries.size());
return;
}
break;
}
if (locations.size() == 1) {
return;
}
ArrayList<Future<ReplicateWALEntryResponse>> tasks =
new ArrayList<Future<ReplicateWALEntryResponse>>(locations.size() - 1);
// All passed entries should belong to one region because it is coming from the EntryBuffers
// split per region. But the regions might split and merge (unlike log recovery case).
for (int replicaId = 0; replicaId < locations.size(); replicaId++) {
HRegionLocation location = locations.getRegionLocation(replicaId);
if (!RegionReplicaUtil.isDefaultReplica(replicaId)) {
HRegionInfo regionInfo =
location == null
? RegionReplicaUtil.getRegionInfoForReplica(
locations.getDefaultRegionLocation().getRegionInfo(), replicaId)
: location.getRegionInfo();
RegionReplicaReplayCallable callable =
new RegionReplicaReplayCallable(
connection,
rpcControllerFactory,
tableName,
location,
regionInfo,
row,
entries,
sink.getSkippedEditsCounter());
Future<ReplicateWALEntryResponse> task =
pool.submit(
new RetryingRpcCallable<ReplicateWALEntryResponse>(
rpcRetryingCallerFactory, callable, operationTimeout));
tasks.add(task);
}
}
boolean tasksCancelled = false;
for (Future<ReplicateWALEntryResponse> task : tasks) {
try {
task.get();
} catch (InterruptedException e) {
throw new InterruptedIOException(e.getMessage());
} catch (ExecutionException e) {
Throwable cause = e.getCause();
if (cause instanceof IOException) {
// The table can be disabled or dropped at this time. For disabled tables, we have no
// cheap mechanism to detect this case because meta does not contain this information.
// HConnection.isTableDisabled() is a zk call which we cannot do for every replay RPC.
// So instead we start the replay RPC with retries and
// check whether the table is dropped or disabled which might cause
// SocketTimeoutException, or RetriesExhaustedException or similar if we get IOE.
if (cause instanceof TableNotFoundException || connection.isTableDisabled(tableName)) {
if (LOG.isTraceEnabled()) {
LOG.trace(
"Skipping "
+ entries.size()
+ " entries in table "
+ tableName
+ " because received exception for dropped or disabled table",
cause);
for (Entry entry : entries) {
LOG.trace("Skipping : " + entry);
}
}
disabledAndDroppedTables.put(tableName, Boolean.TRUE); // put to cache for later.
if (!tasksCancelled) {
sink.getSkippedEditsCounter().addAndGet(entries.size());
tasksCancelled = true; // so that we do not add to skipped counter again
}
continue;
}
// otherwise rethrow
throw (IOException) cause;
}
// unexpected exception
throw new IOException(cause);
}
}
}