/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.client;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.DoNotRetryIOException;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.RegionLocations;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.ipc.HBaseRpcController;
import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.RequestConverter;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
/**
* Caller that goes to replica if the primary region does no answer within a configurable
* timeout. If the timeout is reached, it calls all the secondary replicas, and returns
* the first answer. If the answer comes from one of the secondary replica, it will
* be marked as stale.
*/
@InterfaceAudience.Private
public class RpcRetryingCallerWithReadReplicas {
private static final Log LOG = LogFactory.getLog(RpcRetryingCallerWithReadReplicas.class);
protected final ExecutorService pool;
protected final ClusterConnection cConnection;
protected final Configuration conf;
protected final Get get;
protected final TableName tableName;
protected final int timeBeforeReplicas;
private final int operationTimeout;
private final int rpcTimeout;
private final int retries;
private final RpcControllerFactory rpcControllerFactory;
private final RpcRetryingCallerFactory rpcRetryingCallerFactory;
public RpcRetryingCallerWithReadReplicas(
RpcControllerFactory rpcControllerFactory, TableName tableName,
ClusterConnection cConnection, final Get get,
ExecutorService pool, int retries, int operationTimeout, int rpcTimeout,
int timeBeforeReplicas) {
this.rpcControllerFactory = rpcControllerFactory;
this.tableName = tableName;
this.cConnection = cConnection;
this.conf = cConnection.getConfiguration();
this.get = get;
this.pool = pool;
this.retries = retries;
this.operationTimeout = operationTimeout;
this.rpcTimeout = rpcTimeout;
this.timeBeforeReplicas = timeBeforeReplicas;
this.rpcRetryingCallerFactory = new RpcRetryingCallerFactory(conf);
}
/**
* A RegionServerCallable that takes into account the replicas, i.e.
* - the call can be on any replica
* - we need to stop retrying when the call is completed
* - we can be interrupted
*/
class ReplicaRegionServerCallable extends CancellableRegionServerCallable<Result> {
final int id;
public ReplicaRegionServerCallable(int id, HRegionLocation location) {
super(RpcRetryingCallerWithReadReplicas.this.cConnection,
RpcRetryingCallerWithReadReplicas.this.tableName, get.getRow(),
rpcControllerFactory.newController(), rpcTimeout, new RetryingTimeTracker());
this.id = id;
this.location = location;
}
/**
* 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
// TODO: Very like the super class implemenation. Can we shrink this down?
public void prepare(final boolean reload) throws IOException {
if (getRpcController().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);
}
setStubByServiceName(this.location.getServerName());
}
@Override
// TODO: Very like the super class implemenation. Can we shrink this down?
protected Result rpcCall() throws Exception {
if (getRpcController().isCanceled()) return null;
if (Thread.interrupted()) {
throw new InterruptedIOException();
}
byte[] reg = location.getRegionInfo().getRegionName();
ClientProtos.GetRequest request = RequestConverter.buildGetRequest(reg, get);
HBaseRpcController hrc = (HBaseRpcController)getRpcController();
hrc.reset();
hrc.setCallTimeout(rpcTimeout);
hrc.setPriority(tableName);
ClientProtos.GetResponse response = getStub().get(hrc, request);
if (response == null) {
return null;
}
return ProtobufUtil.toResult(response.getResult(), hrc.cellScanner());
}
}
/**
* <p>
* 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 Result call(int operationTimeout)
throws DoNotRetryIOException, InterruptedIOException, RetriesExhaustedException {
boolean isTargetReplicaSpecified = (get.getReplicaId() >= 0);
RegionLocations rl = getRegionLocations(true, (isTargetReplicaSpecified ? get.getReplicaId()
: RegionReplicaUtil.DEFAULT_REPLICA_ID), cConnection, tableName, get.getRow());
final ResultBoundedCompletionService<Result> cs =
new ResultBoundedCompletionService<>(this.rpcRetryingCallerFactory, pool, rl.size());
int startIndex = 0;
int endIndex = rl.size();
if(isTargetReplicaSpecified) {
addCallsForReplica(cs, rl, get.getReplicaId(), get.getReplicaId());
endIndex = 1;
} 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) {
// We ignore the ExecutionException and continue with the secondary replicas
if (LOG.isDebugEnabled()) {
LOG.debug("Primary replica returns " + e.getCause());
}
// Skip the result from the primary as we know that there is something wrong
startIndex = 1;
} 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 {
Future<Result> f = cs.pollForFirstSuccessfullyCompletedTask(operationTimeout,
TimeUnit.MILLISECONDS, startIndex, endIndex);
if (f == null) {
throw new RetriesExhaustedException("Timed out after " + operationTimeout +
"ms. Get is sent to replicas with startIndex: " + startIndex +
", endIndex: " + endIndex + ", Locations: " + rl);
}
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();
}
LOG.error("Imposible? Arrive at an unreachable line..."); // unreachable
return null; // unreachable
}
/**
* Extract the real exception from the ExecutionException, and throws what makes more
* sense.
*/
static void throwEnrichedException(ExecutionException e, int retries)
throws RetriesExhaustedException, DoNotRetryIOException {
Throwable t = e.getCause();
assert t != null; // That's what ExecutionException is about: holding an exception
if (t instanceof RetriesExhaustedException) {
throw (RetriesExhaustedException) t;
}
if (t instanceof DoNotRetryIOException) {
throw (DoNotRetryIOException) t;
}
RetriesExhaustedException.ThrowableWithExtraContext qt =
new RetriesExhaustedException.ThrowableWithExtraContext(t,
EnvironmentEdgeManager.currentTime(), null);
List<RetriesExhaustedException.ThrowableWithExtraContext> exceptions =
Collections.singletonList(qt);
throw new RetriesExhaustedException(retries, exceptions);
}
/**
* 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, operationTimeout, id);
}
}
static RegionLocations getRegionLocations(boolean useCache, int replicaId,
ClusterConnection cConnection, TableName tableName, byte[] row)
throws RetriesExhaustedException, DoNotRetryIOException, InterruptedIOException {
RegionLocations rl;
try {
if (!useCache) {
rl = cConnection.relocateRegion(tableName, row, replicaId);
} else {
rl = cConnection.locateRegion(tableName, row, useCache, true, replicaId);
}
} catch (DoNotRetryIOException | InterruptedIOException | RetriesExhaustedException e) {
throw e;
} catch (IOException e) {
throw new RetriesExhaustedException("Can't get the location", e);
}
if (rl == null) {
throw new RetriesExhaustedException("Can't get the locations");
}
return rl;
}
}