/**
* 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.io.IOException;
import java.net.InetAddress;
import java.util.List;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.commons.lang.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.CFMetaData;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.ReadCommand;
import org.apache.cassandra.db.ReadResponse;
import org.apache.cassandra.db.Table;
import org.apache.cassandra.net.IAsyncCallback;
import org.apache.cassandra.net.Message;
import org.apache.cassandra.net.MessagingService;
import org.apache.cassandra.thrift.ConsistencyLevel;
import org.apache.cassandra.thrift.UnavailableException;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.SimpleCondition;
import org.apache.cassandra.utils.WrappedRunnable;
public class ReadCallback<T> implements IAsyncCallback
{
protected static final Logger logger = LoggerFactory.getLogger( ReadCallback.class );
public final IResponseResolver<T> resolver;
protected final SimpleCondition condition = new SimpleCondition();
private final long startTime;
protected final int blockfor;
final List<InetAddress> endpoints;
private final IReadCommand command;
protected final AtomicInteger received = new AtomicInteger(0);
/**
* Constructor when response count has to be calculated and blocked for.
*/
public ReadCallback(IResponseResolver<T> resolver, ConsistencyLevel consistencyLevel, IReadCommand command, List<InetAddress> endpoints)
{
this.command = command;
this.blockfor = determineBlockFor(consistencyLevel, command.getKeyspace());
this.resolver = resolver;
this.startTime = System.currentTimeMillis();
boolean repair = randomlyReadRepair();
this.endpoints = repair || resolver instanceof RowRepairResolver
? endpoints
: preferredEndpoints(endpoints);
if (logger.isDebugEnabled())
logger.debug(String.format("Blockfor/repair is %s/%s; setting up requests to %s",
blockfor, repair, StringUtils.join(this.endpoints, ",")));
}
protected List<InetAddress> preferredEndpoints(List<InetAddress> endpoints)
{
return endpoints.subList(0, Math.min(endpoints.size(), blockfor)); // min so as to not throw exception until assureSufficient is called
}
private boolean randomlyReadRepair()
{
if (resolver instanceof RowDigestResolver)
{
assert command instanceof ReadCommand : command;
String table = ((RowDigestResolver) resolver).table;
String columnFamily = ((ReadCommand) command).getColumnFamilyName();
CFMetaData cfmd = DatabaseDescriptor.getTableMetaData(table).get(columnFamily);
return cfmd.getReadRepairChance() > FBUtilities.threadLocalRandom().nextDouble();
}
// we don't read repair on range scans
return false;
}
public T get() throws TimeoutException, DigestMismatchException, IOException
{
long timeout = DatabaseDescriptor.getRpcTimeout() - (System.currentTimeMillis() - startTime);
boolean success;
try
{
success = condition.await(timeout, TimeUnit.MILLISECONDS);
}
catch (InterruptedException ex)
{
throw new AssertionError(ex);
}
if (!success)
{
StringBuilder sb = new StringBuilder("");
for (Message message : resolver.getMessages())
sb.append(message.getFrom()).append(", ");
throw new TimeoutException("Operation timed out - received only " + received.get() + " responses from " + sb.toString() + " .");
}
return blockfor == 1 ? resolver.getData() : resolver.resolve();
}
public void response(Message message)
{
resolver.preprocess(message);
int n = waitingFor(message)
? received.incrementAndGet()
: received.get();
if (n >= blockfor && resolver.isDataPresent())
{
condition.signal();
maybeResolveForRepair();
}
}
/**
* @return true if the message counts towards the blockfor threshold
* TODO turn the Message into a response so we don't need two versions of this method
*/
protected boolean waitingFor(Message message)
{
return true;
}
/**
* @return true if the response counts towards the blockfor threshold
*/
protected boolean waitingFor(ReadResponse response)
{
return true;
}
public void response(ReadResponse result)
{
((RowDigestResolver) resolver).injectPreProcessed(result);
int n = waitingFor(result)
? received.incrementAndGet()
: received.get();
if (n >= blockfor && resolver.isDataPresent())
{
condition.signal();
maybeResolveForRepair();
}
}
/**
* Check digests in the background on the Repair stage if we've received replies
* too all the requests we sent.
*/
protected void maybeResolveForRepair()
{
if (blockfor < endpoints.size() && received.get() == endpoints.size())
{
assert resolver.isDataPresent();
StageManager.getStage(Stage.READ_REPAIR).execute(new AsyncRepairRunner());
}
}
public int determineBlockFor(ConsistencyLevel consistencyLevel, String table)
{
switch (consistencyLevel)
{
case ONE:
case ANY:
return 1;
case TWO:
return 2;
case THREE:
return 3;
case QUORUM:
return (Table.open(table).getReplicationStrategy().getReplicationFactor() / 2) + 1;
case ALL:
return Table.open(table).getReplicationStrategy().getReplicationFactor();
default:
throw new UnsupportedOperationException("invalid consistency level: " + consistencyLevel);
}
}
public void assureSufficientLiveNodes() throws UnavailableException
{
if (endpoints.size() < blockfor)
{
logger.debug("Live nodes {} do not satisfy ConsistencyLevel ({} required)",
StringUtils.join(endpoints, ", "), blockfor);
throw new UnavailableException();
}
}
public boolean isLatencyForSnitch()
{
return true;
}
private class AsyncRepairRunner extends WrappedRunnable
{
protected void runMayThrow() throws IOException
{
try
{
resolver.resolve();
}
catch (DigestMismatchException e)
{
if (logger.isDebugEnabled())
logger.debug("Digest mismatch:", e);
ReadCommand readCommand = (ReadCommand) command;
final RowRepairResolver repairResolver = new RowRepairResolver(readCommand.table, readCommand.key);
IAsyncCallback repairHandler = new AsyncRepairCallback(repairResolver, endpoints.size());
for (InetAddress endpoint : endpoints)
MessagingService.instance().sendRR(readCommand, endpoint, repairHandler);
}
}
}
}