/*
* 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.db.commitlog;
import java.io.*;
import java.lang.management.ManagementFactory;
import java.nio.ByteBuffer;
import java.util.*;
import java.util.concurrent.Future;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.*;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.io.util.ByteBufferOutputStream;
import org.apache.cassandra.io.util.ChecksummedOutputStream;
import org.apache.cassandra.metrics.CommitLogMetrics;
import org.apache.cassandra.net.MessagingService;
import org.apache.cassandra.utils.PureJavaCrc32;
import com.google.common.util.concurrent.Futures;
import static org.apache.cassandra.db.commitlog.CommitLogSegment.*;
/*
* Commit Log tracks every write operation into the system. The aim of the commit log is to be able to
* successfully recover data that was not stored to disk via the Memtable.
*/
public class CommitLog implements CommitLogMBean
{
private static final Logger logger = LoggerFactory.getLogger(CommitLog.class);
public static final CommitLog instance = new CommitLog();
// we only permit records HALF the size of a commit log, to ensure we don't spin allocating many mostly
// empty segments when writing large records
private static final long MAX_MUTATION_SIZE = DatabaseDescriptor.getCommitLogSegmentSize() >> 1;
public final CommitLogSegmentManager allocator;
public final CommitLogArchiver archiver = new CommitLogArchiver();
private final CommitLogMetrics metrics;
final AbstractCommitLogService executor;
private CommitLog()
{
DatabaseDescriptor.createAllDirectories();
allocator = new CommitLogSegmentManager();
executor = DatabaseDescriptor.getCommitLogSync() == Config.CommitLogSync.batch
? new BatchCommitLogService(this)
: new PeriodicCommitLogService(this);
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
try
{
mbs.registerMBean(this, new ObjectName("org.apache.cassandra.db:type=Commitlog"));
}
catch (Exception e)
{
throw new RuntimeException(e);
}
// register metrics
metrics = new CommitLogMetrics(executor, allocator);
}
/**
* Perform recovery on commit logs located in the directory specified by the config file.
*
* @return the number of mutations replayed
*/
public int recover() throws IOException
{
archiver.maybeRestoreArchive();
File[] files = new File(DatabaseDescriptor.getCommitLogLocation()).listFiles(new FilenameFilter()
{
public boolean accept(File dir, String name)
{
// we used to try to avoid instantiating commitlog (thus creating an empty segment ready for writes)
// until after recover was finished. this turns out to be fragile; it is less error-prone to go
// ahead and allow writes before recover(), and just skip active segments when we do.
return CommitLogDescriptor.isValid(name) && !instance.allocator.manages(name);
}
});
int replayed = 0;
if (files.length == 0)
{
logger.info("No commitlog files found; skipping replay");
}
else
{
Arrays.sort(files, new CommitLogSegmentFileComparator());
logger.info("Replaying {}", StringUtils.join(files, ", "));
replayed = recover(files);
logger.info("Log replay complete, {} replayed mutations", replayed);
for (File f : files)
CommitLog.instance.allocator.recycleSegment(f);
}
allocator.enableReserveSegmentCreation();
return replayed;
}
/**
* Perform recovery on a list of commit log files.
*
* @param clogs the list of commit log files to replay
* @return the number of mutations replayed
*/
public int recover(File... clogs) throws IOException
{
CommitLogReplayer recovery = new CommitLogReplayer();
recovery.recover(clogs);
return recovery.blockForWrites();
}
/**
* Perform recovery on a single commit log.
*/
public void recover(String path) throws IOException
{
recover(new File(path));
}
/**
* @return a Future representing a ReplayPosition such that when it is ready,
* all Allocations created prior to the getContext call will be written to the log
*/
public Future<ReplayPosition> getContext()
{
return Futures.immediateFuture(allocator.allocatingFrom().getContext());
}
/**
* Flushes all dirty CFs, waiting for them to free and recycle any segments they were retaining
*/
public void forceRecycleAllSegments()
{
allocator.forceRecycleAll();
}
/**
* Forces a disk flush on the commit log files that need it. Blocking.
*/
public void sync(boolean syncAllSegments)
{
CommitLogSegment current = allocator.allocatingFrom();
for (CommitLogSegment segment : allocator.getActiveSegments())
{
if (!syncAllSegments && segment.id > current.id)
return;
segment.sync();
}
}
/**
* Preempts the CLExecutor, telling to to sync immediately
*/
public void requestExtraSync()
{
executor.requestExtraSync();
}
/**
* Add a Mutation to the commit log.
*
* @param mutation the Mutation to add to the log
*/
public void add(Mutation mutation)
{
long size = Mutation.serializer.serializedSize(mutation, MessagingService.current_version);
long totalSize = size + ENTRY_OVERHEAD_SIZE;
if (totalSize > MAX_MUTATION_SIZE)
{
logger.warn("Skipping commitlog append of extremely large mutation ({} bytes)", totalSize);
return;
}
Allocation alloc = allocator.allocate(mutation, (int) totalSize, new Allocation());
try
{
PureJavaCrc32 checksum = new PureJavaCrc32();
final ByteBuffer buffer = alloc.getBuffer();
DataOutputStream dos = new DataOutputStream(new ChecksummedOutputStream(new ByteBufferOutputStream(buffer), checksum));
// checksummed length
dos.writeInt((int) size);
buffer.putLong(checksum.getValue());
// checksummed mutation
Mutation.serializer.serialize(mutation, dos, MessagingService.current_version);
buffer.putLong(checksum.getValue());
}
catch (IOException e)
{
throw new FSWriteError(e, alloc.getSegment().getPath());
}
finally
{
alloc.markWritten();
}
executor.finishWriteFor(alloc);
}
/**
* Modifies the per-CF dirty cursors of any commit log segments for the column family according to the position
* given. Discards any commit log segments that are no longer used.
*
* @param cfId the column family ID that was flushed
* @param context the replay position of the flush
*/
public void discardCompletedSegments(final UUID cfId, final ReplayPosition context)
{
logger.debug("discard completed log segments for {}, column family {}", context, cfId);
// Go thru the active segment files, which are ordered oldest to newest, marking the
// flushed CF as clean, until we reach the segment file containing the ReplayPosition passed
// in the arguments. Any segments that become unused after they are marked clean will be
// recycled or discarded.
for (Iterator<CommitLogSegment> iter = allocator.getActiveSegments().iterator(); iter.hasNext();)
{
CommitLogSegment segment = iter.next();
segment.markClean(cfId, context);
if (segment.isUnused())
{
logger.debug("Commit log segment {} is unused", segment);
allocator.recycleSegment(segment);
}
else
{
logger.debug("Not safe to delete{} commit log segment {}; dirty is {}",
(iter.hasNext() ? "" : " active"), segment, segment.dirtyString());
}
// Don't mark or try to delete any newer segments once we've reached the one containing the
// position of the flush.
if (segment.contains(context))
break;
}
}
@Override
public long getCompletedTasks()
{
return metrics.completedTasks.value();
}
@Override
public long getPendingTasks()
{
return metrics.pendingTasks.value();
}
/**
* @return the total size occupied by commitlog segments expressed in bytes. (used by MBean)
*/
public long getTotalCommitlogSize()
{
return metrics.totalCommitLogSize.value();
}
public List<String> getActiveSegmentNames()
{
List<String> segmentNames = new ArrayList<>();
for (CommitLogSegment segment : allocator.getActiveSegments())
segmentNames.add(segment.getName());
return segmentNames;
}
public List<String> getArchivingSegmentNames()
{
return new ArrayList<>(archiver.archivePending.keySet());
}
/**
* Shuts down the threads used by the commit log, blocking until completion.
*/
public void shutdownBlocking() throws InterruptedException
{
executor.shutdown();
executor.awaitTermination();
allocator.shutdown();
allocator.awaitTermination();
}
/**
* FOR TESTING PURPOSES. See CommitLogAllocator.
*/
public void resetUnsafe()
{
allocator.resetUnsafe();
}
/**
* Used by tests.
*
* @return the number of active segments (segments with unflushed data in them)
*/
public int activeSegments()
{
return allocator.getActiveSegments().size();
}
}