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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.service;
import java.net.InetAddress;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.concurrent.Stage;
import org.apache.cassandra.concurrent.StageManager;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.partitions.PartitionIterator;
import org.apache.cassandra.exceptions.RequestFailureReason;
import org.apache.cassandra.db.transform.DuplicateRowChecker;
import org.apache.cassandra.exceptions.ReadFailureException;
import org.apache.cassandra.exceptions.ReadTimeoutException;
import org.apache.cassandra.exceptions.UnavailableException;
import org.apache.cassandra.metrics.ReadRepairMetrics;
import org.apache.cassandra.net.IAsyncCallbackWithFailure;
import org.apache.cassandra.net.MessageIn;
import org.apache.cassandra.net.MessageOut;
import org.apache.cassandra.net.MessagingService;
import org.apache.cassandra.db.ConsistencyLevel;
import org.apache.cassandra.tracing.TraceState;
import org.apache.cassandra.tracing.Tracing;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.concurrent.SimpleCondition;
public class ReadCallback implements IAsyncCallbackWithFailure
{
protected static final Logger logger = LoggerFactory.getLogger( ReadCallback.class );
public final ResponseResolver resolver;
private final SimpleCondition condition = new SimpleCondition();
private final long queryStartNanoTime;
final int blockfor;
final List endpoints;
private final ReadCommand command;
private final ConsistencyLevel consistencyLevel;
private static final AtomicIntegerFieldUpdater recievedUpdater
= AtomicIntegerFieldUpdater.newUpdater(ReadCallback.class, "received");
private volatile int received = 0;
private static final AtomicIntegerFieldUpdater failuresUpdater
= AtomicIntegerFieldUpdater.newUpdater(ReadCallback.class, "failures");
private volatile int failures = 0;
private final Map failureReasonByEndpoint;
private final Keyspace keyspace; // TODO push this into ConsistencyLevel?
/**
* Constructor when response count has to be calculated and blocked for.
*/
public ReadCallback(ResponseResolver resolver, ConsistencyLevel consistencyLevel, ReadCommand command, List filteredEndpoints, long queryStartNanoTime)
{
this(resolver,
consistencyLevel,
consistencyLevel.blockFor(Keyspace.open(command.metadata().ksName)),
command,
Keyspace.open(command.metadata().ksName),
filteredEndpoints,
queryStartNanoTime);
}
public ReadCallback(ResponseResolver resolver, ConsistencyLevel consistencyLevel, int blockfor, ReadCommand command, Keyspace keyspace, List endpoints, long queryStartNanoTime)
{
this.command = command;
this.keyspace = keyspace;
this.blockfor = blockfor;
this.consistencyLevel = consistencyLevel;
this.resolver = resolver;
this.queryStartNanoTime = queryStartNanoTime;
this.endpoints = endpoints;
this.failureReasonByEndpoint = new ConcurrentHashMap<>();
// we don't support read repair (or rapid read protection) for range scans yet (CASSANDRA-6897)
assert !(command instanceof PartitionRangeReadCommand) || blockfor >= endpoints.size();
if (logger.isTraceEnabled())
logger.trace("Blockfor is {}; setting up requests to {}", blockfor, StringUtils.join(this.endpoints, ","));
}
public boolean await(long timePastStart, TimeUnit unit)
{
long time = unit.toNanos(timePastStart) - (System.nanoTime() - queryStartNanoTime);
try
{
return condition.await(time, TimeUnit.NANOSECONDS);
}
catch (InterruptedException ex)
{
throw new AssertionError(ex);
}
}
public void awaitResults() throws ReadFailureException, ReadTimeoutException
{
boolean signaled = await(command.getTimeout(), TimeUnit.MILLISECONDS);
boolean failed = blockfor + failures > endpoints.size();
if (signaled && !failed)
return;
if (Tracing.isTracing())
{
String gotData = received > 0 ? (resolver.isDataPresent() ? " (including data)" : " (only digests)") : "";
Tracing.trace("{}; received {} of {} responses{}", new Object[]{ (failed ? "Failed" : "Timed out"), received, blockfor, gotData });
}
else if (logger.isDebugEnabled())
{
String gotData = received > 0 ? (resolver.isDataPresent() ? " (including data)" : " (only digests)") : "";
logger.debug("{}; received {} of {} responses{}", new Object[]{ (failed ? "Failed" : "Timed out"), received, blockfor, gotData });
}
// Same as for writes, see AbstractWriteResponseHandler
throw failed
? new ReadFailureException(consistencyLevel, received, blockfor, resolver.isDataPresent(), failureReasonByEndpoint)
: new ReadTimeoutException(consistencyLevel, received, blockfor, resolver.isDataPresent());
}
public PartitionIterator get() throws ReadFailureException, ReadTimeoutException, DigestMismatchException
{
awaitResults();
PartitionIterator result = blockfor == 1 ? resolver.getData() : resolver.resolve();
if (logger.isTraceEnabled())
logger.trace("Read: {} ms.", TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - queryStartNanoTime));
return DuplicateRowChecker.duringRead(result, endpoints);
}
public int blockFor()
{
return blockfor;
}
public void response(MessageIn message)
{
resolver.preprocess(message);
int n = waitingFor(message.from)
? recievedUpdater.incrementAndGet(this)
: received;
/*
* Ensure that data is present and the response accumulator has properly published the
* responses it has received. This may result in not signaling immediately when we receive
* the minimum number of required results, but it guarantees at least the minimum will
* be accessible when we do signal. (see CASSANDRA-16883)
*/
if (n >= blockfor && resolver.responses.size() >= blockfor && resolver.isDataPresent())
{
condition.signalAll();
// kick off a background digest comparison if this is a result that (may have) arrived after
// the original resolve that get() kicks off as soon as the condition is signaled
if (blockfor < endpoints.size() && n == endpoints.size())
{
TraceState traceState = Tracing.instance.get();
if (traceState != null)
traceState.trace("Initiating read-repair");
StageManager.getStage(Stage.READ_REPAIR).execute(new AsyncRepairRunner(traceState, queryStartNanoTime));
}
}
}
/**
* @return true if the message counts towards the blockfor threshold
*/
private boolean waitingFor(InetAddress from)
{
return !consistencyLevel.isDatacenterLocal() || DatabaseDescriptor.getLocalDataCenter().equals(DatabaseDescriptor.getEndpointSnitch().getDatacenter(from));
}
/**
* @return the current number of received responses
*/
public int getReceivedCount()
{
return received;
}
public void response(ReadResponse result)
{
MessageIn message = MessageIn.create(FBUtilities.getBroadcastAddress(),
result,
Collections.emptyMap(),
MessagingService.Verb.INTERNAL_RESPONSE,
MessagingService.current_version);
response(message);
}
public void assureSufficientLiveNodes() throws UnavailableException
{
consistencyLevel.assureSufficientLiveNodes(keyspace, endpoints);
}
public boolean isLatencyForSnitch()
{
return true;
}
private class AsyncRepairRunner implements Runnable
{
private final TraceState traceState;
private final long queryStartNanoTime;
public AsyncRepairRunner(TraceState traceState, long queryStartNanoTime)
{
this.traceState = traceState;
this.queryStartNanoTime = queryStartNanoTime;
}
public void run()
{
// If the resolver is a DigestResolver, we need to do a full data read if there is a mismatch.
// Otherwise, resolve will send the repairs directly if needs be (and in that case we should never
// get a digest mismatch).
try
{
resolver.compareResponses();
}
catch (DigestMismatchException e)
{
assert resolver instanceof DigestResolver;
if (traceState != null)
traceState.trace("Digest mismatch: {}", e.toString());
ReadRepairMetrics.repairedBackground.mark();
final DataResolver repairResolver = new DataResolver(keyspace, command, consistencyLevel, endpoints.size(), queryStartNanoTime);
AsyncRepairCallback repairHandler = new AsyncRepairCallback(repairResolver, endpoints.size());
for (InetAddress endpoint : endpoints)
{
MessageOut message = command.createMessage(MessagingService.instance().getVersion(endpoint));
MessagingService.instance().sendRR(message, endpoint, repairHandler);
}
}
}
}
@Override
public void onFailure(InetAddress from, RequestFailureReason failureReason)
{
int n = waitingFor(from)
? failuresUpdater.incrementAndGet(this)
: failures;
failureReasonByEndpoint.put(from, failureReason);
if (blockfor + n > endpoints.size())
condition.signalAll();
}
}
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