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/*
* 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.batchlog;
import java.io.IOException;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimap;
import com.google.common.util.concurrent.RateLimiter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.concurrent.DebuggableScheduledThreadPoolExecutor;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.config.SchemaConstants;
import org.apache.cassandra.cql3.UntypedResultSet;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.Keyspace;
import org.apache.cassandra.db.Mutation;
import org.apache.cassandra.db.SystemKeyspace;
import org.apache.cassandra.db.WriteType;
import org.apache.cassandra.db.marshal.BytesType;
import org.apache.cassandra.db.marshal.UUIDType;
import org.apache.cassandra.db.partitions.PartitionUpdate;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.exceptions.WriteFailureException;
import org.apache.cassandra.exceptions.WriteTimeoutException;
import org.apache.cassandra.gms.FailureDetector;
import org.apache.cassandra.hints.Hint;
import org.apache.cassandra.hints.HintsService;
import org.apache.cassandra.io.util.DataInputBuffer;
import org.apache.cassandra.io.util.DataOutputBuffer;
import org.apache.cassandra.net.MessageIn;
import org.apache.cassandra.net.MessageOut;
import org.apache.cassandra.net.MessagingService;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.service.WriteResponseHandler;
import org.apache.cassandra.utils.ExecutorUtils;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.MBeanWrapper;
import org.apache.cassandra.utils.UUIDGen;
import static com.google.common.collect.Iterables.transform;
import static org.apache.cassandra.cql3.QueryProcessor.executeInternal;
import static org.apache.cassandra.cql3.QueryProcessor.executeInternalWithPaging;
public class BatchlogManager implements BatchlogManagerMBean
{
public static final String MBEAN_NAME = "org.apache.cassandra.db:type=BatchlogManager";
private static final long REPLAY_INTERVAL = 10 * 1000; // milliseconds
static final int DEFAULT_PAGE_SIZE = 128;
private static final Logger logger = LoggerFactory.getLogger(BatchlogManager.class);
public static final BatchlogManager instance = new BatchlogManager();
public static final long BATCHLOG_REPLAY_TIMEOUT = Long.getLong("cassandra.batchlog.replay_timeout_in_ms", DatabaseDescriptor.getWriteRpcTimeout() * 2);
private volatile long totalBatchesReplayed = 0; // no concurrency protection necessary as only written by replay thread.
private volatile UUID lastReplayedUuid = UUIDGen.minTimeUUID(0);
// Single-thread executor service for scheduling and serializing log replay.
private final ScheduledExecutorService batchlogTasks;
public BatchlogManager()
{
ScheduledThreadPoolExecutor executor = new DebuggableScheduledThreadPoolExecutor("BatchlogTasks");
executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
batchlogTasks = executor;
}
public void start()
{
MBeanWrapper.instance.registerMBean(this, MBEAN_NAME);
batchlogTasks.scheduleWithFixedDelay(this::replayFailedBatches,
StorageService.RING_DELAY,
REPLAY_INTERVAL,
TimeUnit.MILLISECONDS);
}
public void shutdownAndWait(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException
{
ExecutorUtils.shutdownAndWait(timeout, unit, batchlogTasks);
}
public static void remove(UUID id)
{
new Mutation(PartitionUpdate.fullPartitionDelete(SystemKeyspace.Batches,
UUIDType.instance.decompose(id),
FBUtilities.timestampMicros(),
FBUtilities.nowInSeconds()))
.apply();
}
public static void store(Batch batch)
{
store(batch, true);
}
public static void store(Batch batch, boolean durableWrites)
{
List mutations = new ArrayList<>(batch.encodedMutations.size() + batch.decodedMutations.size());
mutations.addAll(batch.encodedMutations);
for (Mutation mutation : batch.decodedMutations)
{
try (DataOutputBuffer buffer = new DataOutputBuffer())
{
Mutation.serializer.serialize(mutation, buffer, MessagingService.current_version);
mutations.add(buffer.buffer());
}
catch (IOException e)
{
// shouldn't happen
throw new AssertionError(e);
}
}
PartitionUpdate.SimpleBuilder builder = PartitionUpdate.simpleBuilder(SystemKeyspace.Batches, batch.id);
builder.row()
.timestamp(batch.creationTime)
.add("version", MessagingService.current_version)
.appendAll("mutations", mutations);
builder.buildAsMutation().apply(durableWrites);
}
@VisibleForTesting
public int countAllBatches()
{
String query = String.format("SELECT count(*) FROM %s.%s", SchemaConstants.SYSTEM_KEYSPACE_NAME, SystemKeyspace.BATCHES);
UntypedResultSet results = executeInternal(query);
if (results == null || results.isEmpty())
return 0;
return (int) results.one().getLong("count");
}
public long getTotalBatchesReplayed()
{
return totalBatchesReplayed;
}
public void forceBatchlogReplay() throws Exception
{
startBatchlogReplay().get();
}
public Future startBatchlogReplay()
{
// If a replay is already in progress this request will be executed after it completes.
return batchlogTasks.submit(this::replayFailedBatches);
}
void performInitialReplay() throws InterruptedException, ExecutionException
{
// Invokes initial replay. Used for testing only.
batchlogTasks.submit(this::replayFailedBatches).get();
}
private void replayFailedBatches()
{
logger.trace("Started replayFailedBatches");
// rate limit is in bytes per second. Uses Double.MAX_VALUE if disabled (set to 0 in cassandra.yaml).
// max rate is scaled by the number of nodes in the cluster (same as for HHOM - see CASSANDRA-5272).
int endpointsCount = StorageService.instance.getTokenMetadata().getAllEndpoints().size();
if (endpointsCount <= 0)
{
logger.trace("Replay cancelled as there are no peers in the ring.");
return;
}
int throttleInKB = DatabaseDescriptor.getBatchlogReplayThrottleInKB() / endpointsCount;
RateLimiter rateLimiter = RateLimiter.create(throttleInKB == 0 ? Double.MAX_VALUE : throttleInKB * 1024);
UUID limitUuid = UUIDGen.maxTimeUUID(System.currentTimeMillis() - getBatchlogTimeout());
ColumnFamilyStore store = Keyspace.open(SchemaConstants.SYSTEM_KEYSPACE_NAME).getColumnFamilyStore(SystemKeyspace.BATCHES);
int pageSize = calculatePageSize(store);
// There cannot be any live content where token(id) <= token(lastReplayedUuid) as every processed batch is
// deleted, but the tombstoned content may still be present in the tables. To avoid walking over it we specify
// token(id) > token(lastReplayedUuid) as part of the query.
String query = String.format("SELECT id, mutations, version FROM %s.%s WHERE token(id) > token(?) AND token(id) <= token(?)",
SchemaConstants.SYSTEM_KEYSPACE_NAME,
SystemKeyspace.BATCHES);
UntypedResultSet batches = executeInternalWithPaging(query, pageSize, lastReplayedUuid, limitUuid);
processBatchlogEntries(batches, pageSize, rateLimiter);
lastReplayedUuid = limitUuid;
logger.trace("Finished replayFailedBatches");
}
// read less rows (batches) per page if they are very large
static int calculatePageSize(ColumnFamilyStore store)
{
double averageRowSize = store.getMeanPartitionSize();
if (averageRowSize <= 0)
return DEFAULT_PAGE_SIZE;
return (int) Math.max(1, Math.min(DEFAULT_PAGE_SIZE, 4 * 1024 * 1024 / averageRowSize));
}
private void processBatchlogEntries(UntypedResultSet batches, int pageSize, RateLimiter rateLimiter)
{
int positionInPage = 0;
ArrayList unfinishedBatches = new ArrayList<>(pageSize);
Set hintedNodes = new HashSet<>();
Set replayedBatches = new HashSet<>();
// Sending out batches for replay without waiting for them, so that one stuck batch doesn't affect others
for (UntypedResultSet.Row row : batches)
{
UUID id = row.getUUID("id");
int version = row.getInt("version");
try
{
ReplayingBatch batch = new ReplayingBatch(id, version, row.getList("mutations", BytesType.instance));
if (batch.replay(rateLimiter, hintedNodes) > 0)
{
unfinishedBatches.add(batch);
}
else
{
remove(id); // no write mutations were sent (either expired or all CFs involved truncated).
++totalBatchesReplayed;
}
}
catch (IOException e)
{
logger.warn("Skipped batch replay of {} due to {}", id, e);
remove(id);
}
if (++positionInPage == pageSize)
{
// We have reached the end of a batch. To avoid keeping more than a page of mutations in memory,
// finish processing the page before requesting the next row.
finishAndClearBatches(unfinishedBatches, hintedNodes, replayedBatches);
positionInPage = 0;
}
}
finishAndClearBatches(unfinishedBatches, hintedNodes, replayedBatches);
// to preserve batch guarantees, we must ensure that hints (if any) have made it to disk, before deleting the batches
HintsService.instance.flushAndFsyncBlockingly(transform(hintedNodes, StorageService.instance::getHostIdForEndpoint));
// once all generated hints are fsynced, actually delete the batches
replayedBatches.forEach(BatchlogManager::remove);
}
private void finishAndClearBatches(ArrayList batches, Set hintedNodes, Set replayedBatches)
{
// schedule hints for timed out deliveries
for (ReplayingBatch batch : batches)
{
batch.finish(hintedNodes);
replayedBatches.add(batch.id);
}
totalBatchesReplayed += batches.size();
batches.clear();
}
public static long getBatchlogTimeout()
{
return BATCHLOG_REPLAY_TIMEOUT; // enough time for the actual write + BM removal mutation
}
private static class ReplayingBatch
{
private final UUID id;
private final long writtenAt;
private final List mutations;
private final int replayedBytes;
private List> replayHandlers;
ReplayingBatch(UUID id, int version, List serializedMutations) throws IOException
{
this.id = id;
this.writtenAt = UUIDGen.unixTimestamp(id);
this.mutations = new ArrayList<>(serializedMutations.size());
this.replayedBytes = addMutations(version, serializedMutations);
}
public int replay(RateLimiter rateLimiter, Set hintedNodes) throws IOException
{
logger.trace("Replaying batch {}", id);
if (mutations.isEmpty())
return 0;
int gcgs = gcgs(mutations);
if (TimeUnit.MILLISECONDS.toSeconds(writtenAt) + gcgs <= FBUtilities.nowInSeconds())
return 0;
replayHandlers = sendReplays(mutations, writtenAt, hintedNodes);
rateLimiter.acquire(replayedBytes); // acquire afterwards, to not mess up ttl calculation.
return replayHandlers.size();
}
public void finish(Set hintedNodes)
{
for (int i = 0; i < replayHandlers.size(); i++)
{
ReplayWriteResponseHandler handler = replayHandlers.get(i);
try
{
handler.get();
}
catch (WriteTimeoutException|WriteFailureException e)
{
logger.trace("Failed replaying a batched mutation to a node, will write a hint");
logger.trace("Failure was : {}", e.getMessage());
// writing hints for the rest to hints, starting from i
writeHintsForUndeliveredEndpoints(i, hintedNodes);
return;
}
}
}
private int addMutations(int version, List serializedMutations) throws IOException
{
int ret = 0;
for (ByteBuffer serializedMutation : serializedMutations)
{
ret += serializedMutation.remaining();
try (DataInputBuffer in = new DataInputBuffer(serializedMutation, true))
{
addMutation(Mutation.serializer.deserialize(in, version));
}
}
return ret;
}
// Remove CFs that have been truncated since. writtenAt and SystemTable#getTruncatedAt() both return millis.
// We don't abort the replay entirely b/c this can be considered a success (truncated is same as delivered then
// truncated.
private void addMutation(Mutation mutation)
{
for (UUID cfId : mutation.getColumnFamilyIds())
if (writtenAt <= SystemKeyspace.getTruncatedAt(cfId))
mutation = mutation.without(cfId);
if (!mutation.isEmpty())
mutations.add(mutation);
}
private void writeHintsForUndeliveredEndpoints(int startFrom, Set hintedNodes)
{
int gcgs = gcgs(mutations);
// expired
if (TimeUnit.MILLISECONDS.toSeconds(writtenAt) + gcgs <= FBUtilities.nowInSeconds())
return;
for (int i = startFrom; i < replayHandlers.size(); i++)
{
ReplayWriteResponseHandler handler = replayHandlers.get(i);
Mutation undeliveredMutation = mutations.get(i);
if (handler != null)
{
hintedNodes.addAll(handler.undelivered);
HintsService.instance.write(transform(handler.undelivered, StorageService.instance::getHostIdForEndpoint),
Hint.create(undeliveredMutation, writtenAt));
}
}
}
private static List> sendReplays(List mutations,
long writtenAt,
Set hintedNodes)
{
List> handlers = new ArrayList<>(mutations.size());
for (Mutation mutation : mutations)
{
ReplayWriteResponseHandler handler = sendSingleReplayMutation(mutation, writtenAt, hintedNodes);
if (handler != null)
handlers.add(handler);
}
return handlers;
}
/**
* We try to deliver the mutations to the replicas ourselves if they are alive and only resort to writing hints
* when a replica is down or a write request times out.
*
* @return direct delivery handler to wait on or null, if no live nodes found
*/
private static ReplayWriteResponseHandler sendSingleReplayMutation(final Mutation mutation,
long writtenAt,
Set hintedNodes)
{
Set liveEndpoints = new HashSet<>();
String ks = mutation.getKeyspaceName();
Token tk = mutation.key().getToken();
for (InetAddress endpoint : StorageService.instance.getNaturalAndPendingEndpoints(ks, tk))
{
if (endpoint.equals(FBUtilities.getBroadcastAddress()))
{
mutation.apply();
}
else if (FailureDetector.instance.isAlive(endpoint))
{
liveEndpoints.add(endpoint); // will try delivering directly instead of writing a hint.
}
else
{
hintedNodes.add(endpoint);
HintsService.instance.write(StorageService.instance.getHostIdForEndpoint(endpoint),
Hint.create(mutation, writtenAt));
}
}
if (liveEndpoints.isEmpty())
return null;
ReplayWriteResponseHandler handler = new ReplayWriteResponseHandler<>(liveEndpoints, System.nanoTime());
MessageOut message = mutation.createMessage();
for (InetAddress endpoint : liveEndpoints)
MessagingService.instance().sendRR(message, endpoint, handler, false);
return handler;
}
private static int gcgs(Collection mutations)
{
int gcgs = Integer.MAX_VALUE;
for (Mutation mutation : mutations)
gcgs = Math.min(gcgs, mutation.smallestGCGS());
return gcgs;
}
/**
* A wrapper of WriteResponseHandler that stores the addresses of the endpoints from
* which we did not receive a successful reply.
*/
private static class ReplayWriteResponseHandler extends WriteResponseHandler
{
private final Set undelivered = Collections.newSetFromMap(new ConcurrentHashMap<>());
ReplayWriteResponseHandler(Collection writeEndpoints, long queryStartNanoTime)
{
super(writeEndpoints, Collections.emptySet(), null, null, null, WriteType.UNLOGGED_BATCH, queryStartNanoTime);
undelivered.addAll(writeEndpoints);
}
@Override
protected int totalBlockFor()
{
return this.naturalEndpoints.size();
}
@Override
public void response(MessageIn m)
{
boolean removed = undelivered.remove(m == null ? FBUtilities.getBroadcastAddress() : m.from);
assert removed;
super.response(m);
}
}
}
public static class EndpointFilter
{
private final String localRack;
private final Multimap endpoints;
public EndpointFilter(String localRack, Multimap endpoints)
{
this.localRack = localRack;
this.endpoints = endpoints;
}
/**
* @return list of candidates for batchlog hosting. If possible these will be two nodes from different racks.
*/
public Collection filter()
{
// special case for single-node data centers
if (endpoints.values().size() == 1)
return endpoints.values();
// strip out dead endpoints and localhost
ListMultimap validated = ArrayListMultimap.create();
for (Map.Entry entry : endpoints.entries())
if (isValid(entry.getValue()))
validated.put(entry.getKey(), entry.getValue());
if (validated.size() <= 2)
return validated.values();
if (validated.size() - validated.get(localRack).size() >= 2)
{
// we have enough endpoints in other racks
validated.removeAll(localRack);
}
if (validated.keySet().size() == 1)
{
/*
* we have only 1 `other` rack to select replicas from (whether it be the local rack or a single non-local rack)
* pick two random nodes from there; we are guaranteed to have at least two nodes in the single remaining rack
* because of the preceding if block.
*/
List otherRack = Lists.newArrayList(validated.values());
shuffle(otherRack);
return otherRack.subList(0, 2);
}
// randomize which racks we pick from if more than 2 remaining
Collection racks;
if (validated.keySet().size() == 2)
{
racks = validated.keySet();
}
else
{
racks = Lists.newArrayList(validated.keySet());
shuffle((List) racks);
}
// grab a random member of up to two racks
List result = new ArrayList<>(2);
for (String rack : Iterables.limit(racks, 2))
{
List rackMembers = validated.get(rack);
result.add(rackMembers.get(getRandomInt(rackMembers.size())));
}
return result;
}
@VisibleForTesting
protected boolean isValid(InetAddress input)
{
return !input.equals(FBUtilities.getBroadcastAddress()) && FailureDetector.instance.isAlive(input);
}
@VisibleForTesting
protected int getRandomInt(int bound)
{
return ThreadLocalRandom.current().nextInt(bound);
}
@VisibleForTesting
protected void shuffle(List list)
{
Collections.shuffle(list);
}
}
}
