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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.hints;
import java.io.IOException;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.function.Predicate;
import javax.annotation.Nullable;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import org.apache.cassandra.io.util.File;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.gms.FailureDetector;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.locator.InetAddressAndPort;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.utils.SyncUtil;
import static org.apache.cassandra.utils.Clock.Global.currentTimeMillis;
/**
* Encapsulates the state of a peer's hints: the queue of hints files for dispatch, and the current writer (if any).
*
* The queue for dispatch is multi-threading safe.
*
* The writer MUST only be accessed by {@link HintsWriteExecutor}.
*/
final class HintsStore
{
private static final Logger logger = LoggerFactory.getLogger(HintsStore.class);
public final UUID hostId;
private final File hintsDirectory;
private final ImmutableMap writerParams;
private final Map dispatchPositions;
private final Deque dispatchDequeue;
private final Queue corruptedFiles;
private final Map hintsExpirations;
// last timestamp used in a descriptor; make sure to not reuse the same timestamp for new descriptors.
private volatile long lastUsedTimestamp;
private volatile HintsWriter hintsWriter;
private HintsStore(UUID hostId, File hintsDirectory, ImmutableMap writerParams, List descriptors)
{
this.hostId = hostId;
this.hintsDirectory = hintsDirectory;
this.writerParams = writerParams;
dispatchPositions = new ConcurrentHashMap<>();
dispatchDequeue = new ConcurrentLinkedDeque<>(descriptors);
corruptedFiles = new ConcurrentLinkedQueue<>();
hintsExpirations = new ConcurrentHashMap<>();
//noinspection resource
lastUsedTimestamp = descriptors.stream().mapToLong(d -> d.timestamp).max().orElse(0L);
}
static HintsStore create(UUID hostId, File hintsDirectory, ImmutableMap writerParams, List descriptors)
{
descriptors.sort((d1, d2) -> Long.compare(d1.timestamp, d2.timestamp));
return new HintsStore(hostId, hintsDirectory, writerParams, descriptors);
}
@VisibleForTesting
int getDispatchQueueSize()
{
return dispatchDequeue.size();
}
@VisibleForTesting
int getHintsExpirationsMapSize()
{
return hintsExpirations.size();
}
InetAddressAndPort address()
{
return StorageService.instance.getEndpointForHostId(hostId);
}
@Nullable
PendingHintsInfo getPendingHintsInfo()
{
Iterator descriptors = dispatchDequeue.iterator();
int queueSize = 0;
long minTimestamp = Long.MAX_VALUE;
long maxTimestamp = Long.MIN_VALUE;
while (descriptors.hasNext())
{
HintsDescriptor descriptor = descriptors.next();
minTimestamp = Math.min(minTimestamp, descriptor.timestamp);
maxTimestamp = Math.max(maxTimestamp, descriptor.timestamp);
queueSize++;
}
if (queueSize == 0)
return null;
return new PendingHintsInfo(hostId, queueSize, minTimestamp, maxTimestamp);
}
boolean isLive()
{
InetAddressAndPort address = address();
return address != null && FailureDetector.instance.isAlive(address);
}
HintsDescriptor poll()
{
return dispatchDequeue.poll();
}
void offerFirst(HintsDescriptor descriptor)
{
dispatchDequeue.offerFirst(descriptor);
}
void offerLast(HintsDescriptor descriptor)
{
dispatchDequeue.offerLast(descriptor);
}
void deleteAllHints()
{
HintsDescriptor descriptor;
while ((descriptor = poll()) != null)
{
cleanUp(descriptor);
delete(descriptor);
}
while ((descriptor = corruptedFiles.poll()) != null)
{
cleanUp(descriptor);
delete(descriptor);
}
}
void deleteExpiredHints(long now)
{
deleteHints(it -> hasExpired(it, now));
}
private boolean hasExpired(HintsDescriptor descriptor, long now)
{
Long cachedExpiresAt = hintsExpirations.get(descriptor);
if (null != cachedExpiresAt)
return cachedExpiresAt <= now;
File hintFile = new File(hintsDirectory, descriptor.fileName());
// the file does not exist or if an I/O error occurs
if (!hintFile.exists() || hintFile.lastModified() == 0)
return false;
// 'lastModified' can be considered as the upper bound of the hint creation time.
// So the TTL upper bound of all hints in the file can be estimated by lastModified + maxGcgs of all tables
long ttl = hintFile.lastModified() + Schema.instance.largestGcgs();
hintsExpirations.put(descriptor, ttl);
return ttl <= now;
}
private void deleteHints(Predicate predicate)
{
Set removeSet = new HashSet<>();
try
{
for (HintsDescriptor descriptor : Iterables.concat(dispatchDequeue, corruptedFiles))
{
if (predicate.test(descriptor))
{
cleanUp(descriptor);
delete(descriptor);
removeSet.add(descriptor);
}
}
}
finally // remove the already deleted hints from internal queues in case of exception
{
dispatchDequeue.removeAll(removeSet);
corruptedFiles.removeAll(removeSet);
}
}
void delete(HintsDescriptor descriptor)
{
File hintsFile = descriptor.file(hintsDirectory);
if (hintsFile.tryDelete())
logger.info("Deleted hint file {}", descriptor.fileName());
else if (hintsFile.exists())
logger.error("Failed to delete hint file {}", descriptor.fileName());
else
logger.info("Already deleted hint file {}", descriptor.fileName());
//noinspection ResultOfMethodCallIgnored
descriptor.checksumFile(hintsDirectory).tryDelete();
}
boolean hasFiles()
{
return !dispatchDequeue.isEmpty();
}
InputPosition getDispatchOffset(HintsDescriptor descriptor)
{
return dispatchPositions.get(descriptor);
}
void markDispatchOffset(HintsDescriptor descriptor, InputPosition inputPosition)
{
dispatchPositions.put(descriptor, inputPosition);
}
/**
* @return the total size of all files belonging to the hints store, in bytes.
*/
long getTotalFileSize()
{
long total = 0;
for (HintsDescriptor descriptor : Iterables.concat(dispatchDequeue, corruptedFiles))
{
total += descriptor.file(hintsDirectory).length();
}
return total;
}
void cleanUp(HintsDescriptor descriptor)
{
dispatchPositions.remove(descriptor);
hintsExpirations.remove(descriptor);
}
void markCorrupted(HintsDescriptor descriptor)
{
corruptedFiles.add(descriptor);
}
/**
* @return a copy of the first {@link HintsDescriptor} in the queue for dispatch or {@code null} if queue is empty.
*/
HintsDescriptor getFirstDescriptor()
{
return dispatchDequeue.peekFirst();
}
/*
* Methods dealing with HintsWriter.
*
* All of these, with the exception of isWriting(), are for exclusively single-threaded use by HintsWriteExecutor.
*/
boolean isWriting()
{
return hintsWriter != null;
}
HintsWriter getOrOpenWriter()
{
if (hintsWriter == null)
hintsWriter = openWriter();
return hintsWriter;
}
HintsWriter getWriter()
{
return hintsWriter;
}
private HintsWriter openWriter()
{
lastUsedTimestamp = Math.max(currentTimeMillis(), lastUsedTimestamp + 1);
HintsDescriptor descriptor = new HintsDescriptor(hostId, lastUsedTimestamp, writerParams);
try
{
return HintsWriter.create(hintsDirectory, descriptor);
}
catch (IOException e)
{
throw new FSWriteError(e, descriptor.fileName());
}
}
void closeWriter()
{
if (hintsWriter != null)
{
hintsWriter.close();
offerLast(hintsWriter.descriptor());
hintsWriter = null;
SyncUtil.trySyncDir(hintsDirectory);
}
}
void fsyncWriter()
{
if (hintsWriter != null)
hintsWriter.fsync();
}
}