db: Import db/commmitlog/*
Signed-off-by: Calle Wilund <calle@cloudius-systems.com>
This commit is contained in:
Calle Wilund
Avi Kivity
632
db/commitlog/CommitLogSegment.java
Normal file
632
db/commitlog/CommitLogSegment.java
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@@ -0,0 +1,632 @@
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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.cassandra.db.commitlog;
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import java.io.File;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.ByteBuffer;
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import java.nio.MappedByteBuffer;
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import java.nio.channels.FileChannel;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Comparator;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.UUID;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.atomic.AtomicInteger;
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import org.cliffc.high_scale_lib.NonBlockingHashMap;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.apache.cassandra.config.CFMetaData;
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import org.apache.cassandra.config.DatabaseDescriptor;
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import org.apache.cassandra.config.Schema;
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import org.apache.cassandra.db.ColumnFamily;
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import org.apache.cassandra.db.Mutation;
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import org.apache.cassandra.io.FSWriteError;
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import org.apache.cassandra.io.util.FileUtils;
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import org.apache.cassandra.utils.CLibrary;
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import org.apache.cassandra.utils.PureJavaCrc32;
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import org.apache.cassandra.utils.concurrent.OpOrder;
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import org.apache.cassandra.utils.concurrent.WaitQueue;
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/*
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* A single commit log file on disk. Manages creation of the file and writing mutations to disk,
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* as well as tracking the last mutation position of any "dirty" CFs covered by the segment file. Segment
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* files are initially allocated to a fixed size and can grow to accomidate a larger value if necessary.
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*/
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public class CommitLogSegment
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{
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private static final Logger logger = LoggerFactory.getLogger(CommitLogSegment.class);
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private final static long idBase;
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private final static AtomicInteger nextId = new AtomicInteger(1);
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static
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{
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long maxId = Long.MIN_VALUE;
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for (File file : new File(DatabaseDescriptor.getCommitLogLocation()).listFiles())
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{
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if (CommitLogDescriptor.isValid(file.getName()))
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maxId = Math.max(CommitLogDescriptor.fromFileName(file.getName()).id, maxId);
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}
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idBase = Math.max(System.currentTimeMillis(), maxId + 1);
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}
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// The commit log entry overhead in bytes (int: length + int: head checksum + int: tail checksum)
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public static final int ENTRY_OVERHEAD_SIZE = 4 + 4 + 4;
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// The commit log (chained) sync marker/header size in bytes (int: length + int: checksum [segmentId, position])
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static final int SYNC_MARKER_SIZE = 4 + 4;
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// The OpOrder used to order appends wrt sync
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private final OpOrder appendOrder = new OpOrder();
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private final AtomicInteger allocatePosition = new AtomicInteger();
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// Everything before this offset has been synced and written. The SYNC_MARKER_SIZE bytes after
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// each sync are reserved, and point forwards to the next such offset. The final
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// sync marker in a segment will be zeroed out, or point to EOF.
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private volatile int lastSyncedOffset;
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// the amount of the tail of the file we have allocated but not used - this is used when we discard a log segment
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// to ensure nobody writes to it after we've decided we're done with it
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private int discardedTailFrom;
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// a signal for writers to wait on to confirm the log message they provided has been written to disk
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private final WaitQueue syncComplete = new WaitQueue();
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// a map of Cf->dirty position; this is used to permit marking Cfs clean whilst the log is still in use
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private final NonBlockingHashMap<UUID, AtomicInteger> cfDirty = new NonBlockingHashMap<>(1024);
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// a map of Cf->clean position; this is used to permit marking Cfs clean whilst the log is still in use
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private final ConcurrentHashMap<UUID, AtomicInteger> cfClean = new ConcurrentHashMap<>();
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public final long id;
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private final File logFile;
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private final RandomAccessFile logFileAccessor;
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private final int fd;
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private final MappedByteBuffer buffer;
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public final CommitLogDescriptor descriptor;
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/**
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* @return a newly minted segment file
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*/
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static CommitLogSegment freshSegment()
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{
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return new CommitLogSegment(null);
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}
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static long getNextId()
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{
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return idBase + nextId.getAndIncrement();
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}
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/**
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* Constructs a new segment file.
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*
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* @param filePath if not null, recycles the existing file by renaming it and truncating it to CommitLog.SEGMENT_SIZE.
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*/
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CommitLogSegment(String filePath)
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{
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id = getNextId();
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descriptor = new CommitLogDescriptor(id);
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logFile = new File(DatabaseDescriptor.getCommitLogLocation(), descriptor.fileName());
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boolean isCreating = true;
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try
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{
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if (filePath != null)
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{
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File oldFile = new File(filePath);
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if (oldFile.exists())
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{
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logger.debug("Re-using discarded CommitLog segment for {} from {}", id, filePath);
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if (!oldFile.renameTo(logFile))
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throw new IOException("Rename from " + filePath + " to " + id + " failed");
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isCreating = false;
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}
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}
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// Open the initial the segment file
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logFileAccessor = new RandomAccessFile(logFile, "rw");
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if (isCreating)
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logger.debug("Creating new commit log segment {}", logFile.getPath());
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// Map the segment, extending or truncating it to the standard segment size.
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// (We may have restarted after a segment size configuration change, leaving "incorrectly"
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// sized segments on disk.)
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logFileAccessor.setLength(DatabaseDescriptor.getCommitLogSegmentSize());
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fd = CLibrary.getfd(logFileAccessor.getFD());
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buffer = logFileAccessor.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, DatabaseDescriptor.getCommitLogSegmentSize());
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// write the header
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CommitLogDescriptor.writeHeader(buffer, descriptor);
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// mark the initial sync marker as uninitialised
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buffer.putInt(CommitLogDescriptor.HEADER_SIZE, 0);
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buffer.putLong(CommitLogDescriptor.HEADER_SIZE + 4, 0);
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allocatePosition.set(CommitLogDescriptor.HEADER_SIZE + SYNC_MARKER_SIZE);
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lastSyncedOffset = CommitLogDescriptor.HEADER_SIZE;
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}
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catch (IOException e)
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{
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throw new FSWriteError(e, logFile);
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}
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}
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/**
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* Allocate space in this buffer for the provided mutation, and return the allocated Allocation object.
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* Returns null if there is not enough space in this segment, and a new segment is needed.
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*/
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Allocation allocate(Mutation mutation, int size)
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{
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final OpOrder.Group opGroup = appendOrder.start();
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try
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{
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int position = allocate(size);
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if (position < 0)
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{
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opGroup.close();
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return null;
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}
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markDirty(mutation, position);
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return new Allocation(this, opGroup, position, (ByteBuffer) buffer.duplicate().position(position).limit(position + size));
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}
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catch (Throwable t)
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{
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opGroup.close();
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throw t;
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}
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}
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// allocate bytes in the segment, or return -1 if not enough space
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private int allocate(int size)
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{
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while (true)
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{
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int prev = allocatePosition.get();
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int next = prev + size;
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if (next >= buffer.capacity())
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return -1;
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if (allocatePosition.compareAndSet(prev, next))
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return prev;
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}
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}
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// ensures no more of this segment is writeable, by allocating any unused section at the end and marking it discarded
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void discardUnusedTail()
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{
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// we guard this with the OpOrdering instead of synchronised due to potential dead-lock with CLSM.advanceAllocatingFrom()
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// this actually isn't strictly necessary, as currently all calls to discardUnusedTail occur within a block
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// already protected by this OpOrdering, but to prevent future potential mistakes, we duplicate the protection here
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// so that the contract between discardUnusedTail() and sync() is more explicit.
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try (OpOrder.Group group = appendOrder.start())
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{
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while (true)
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{
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int prev = allocatePosition.get();
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// we set allocatePosition past buffer.capacity() to make sure we always set discardedTailFrom
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int next = buffer.capacity() + 1;
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if (prev == next)
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return;
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if (allocatePosition.compareAndSet(prev, next))
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{
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discardedTailFrom = prev;
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return;
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}
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}
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}
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}
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/**
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* Wait for any appends or discardUnusedTail() operations started before this method was called
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*/
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void waitForModifications()
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{
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// issue a barrier and wait for it
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appendOrder.awaitNewBarrier();
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}
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/**
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* Forces a disk flush for this segment file.
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*/
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synchronized void sync()
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{
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try
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{
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// check we have more work to do
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if (allocatePosition.get() <= lastSyncedOffset + SYNC_MARKER_SIZE)
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return;
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// allocate a new sync marker; this is both necessary in itself, but also serves to demarcate
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// the point at which we can safely consider records to have been completely written to
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int nextMarker;
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nextMarker = allocate(SYNC_MARKER_SIZE);
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boolean close = false;
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if (nextMarker < 0)
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{
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// ensure no more of this CLS is writeable, and mark ourselves for closing
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discardUnusedTail();
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close = true;
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// wait for modifications guards both discardedTailFrom, and any outstanding appends
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waitForModifications();
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if (discardedTailFrom < buffer.capacity() - SYNC_MARKER_SIZE)
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{
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// if there's room in the discard section to write an empty header, use that as the nextMarker
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nextMarker = discardedTailFrom;
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}
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else
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{
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// not enough space left in the buffer, so mark the next sync marker as the EOF position
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nextMarker = buffer.capacity();
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}
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}
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else
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{
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waitForModifications();
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}
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assert nextMarker > lastSyncedOffset;
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// write previous sync marker to point to next sync marker
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// we don't chain the crcs here to ensure this method is idempotent if it fails
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int offset = lastSyncedOffset;
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final PureJavaCrc32 crc = new PureJavaCrc32();
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crc.updateInt((int) (id & 0xFFFFFFFFL));
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crc.updateInt((int) (id >>> 32));
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crc.updateInt(offset);
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buffer.putInt(offset, nextMarker);
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buffer.putInt(offset + 4, crc.getCrc());
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// zero out the next sync marker so replayer can cleanly exit
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if (nextMarker < buffer.capacity())
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{
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buffer.putInt(nextMarker, 0);
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buffer.putInt(nextMarker + 4, 0);
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}
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// actually perform the sync and signal those waiting for it
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buffer.force();
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if (close)
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nextMarker = buffer.capacity();
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lastSyncedOffset = nextMarker;
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syncComplete.signalAll();
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CLibrary.trySkipCache(fd, offset, nextMarker);
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if (close)
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close();
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}
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catch (Exception e) // MappedByteBuffer.force() does not declare IOException but can actually throw it
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{
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throw new FSWriteError(e, getPath());
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}
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}
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public boolean isStillAllocating()
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{
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return allocatePosition.get() < buffer.capacity();
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}
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/**
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* Completely discards a segment file by deleting it. (Potentially blocking operation)
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*/
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void delete()
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{
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FileUtils.deleteWithConfirm(logFile);
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}
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/**
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* Recycle processes an unneeded segment file for reuse.
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*
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* @return a new CommitLogSegment representing the newly reusable segment.
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*/
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CommitLogSegment recycle()
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{
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try
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{
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sync();
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}
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catch (FSWriteError e)
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{
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logger.error("I/O error flushing {} {}", this, e.getMessage());
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throw e;
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}
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close();
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return new CommitLogSegment(getPath());
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}
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/**
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* @return the current ReplayPosition for this log segment
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*/
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public ReplayPosition getContext()
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{
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return new ReplayPosition(id, allocatePosition.get());
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}
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/**
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* @return the file path to this segment
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*/
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public String getPath()
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{
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return logFile.getPath();
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}
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/**
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* @return the file name of this segment
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*/
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public String getName()
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{
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return logFile.getName();
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}
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void waitForFinalSync()
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{
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while (true)
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{
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WaitQueue.Signal signal = syncComplete.register();
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if (lastSyncedOffset < buffer.capacity())
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{
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signal.awaitUninterruptibly();
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}
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else
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{
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signal.cancel();
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break;
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}
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}
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}
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/**
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* Close the segment file.
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*/
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void close()
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{
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try
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{
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if (FileUtils.isCleanerAvailable())
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FileUtils.clean(buffer);
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logFileAccessor.close();
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}
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catch (IOException e)
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{
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throw new FSWriteError(e, getPath());
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}
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}
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void markDirty(Mutation mutation, int allocatedPosition)
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{
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for (ColumnFamily columnFamily : mutation.getColumnFamilies())
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{
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// check for deleted CFS
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CFMetaData cfm = columnFamily.metadata();
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if (cfm.isPurged())
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logger.error("Attempted to write commit log entry for unrecognized table: {}", columnFamily.id());
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else
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ensureAtleast(cfDirty, cfm.cfId, allocatedPosition);
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}
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}
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/**
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* Marks the ColumnFamily specified by cfId as clean for this log segment. If the
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* given context argument is contained in this file, it will only mark the CF as
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* clean if no newer writes have taken place.
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*
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* @param cfId the column family ID that is now clean
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* @param context the optional clean offset
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*/
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public synchronized void markClean(UUID cfId, ReplayPosition context)
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{
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if (!cfDirty.containsKey(cfId))
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return;
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if (context.segment == id)
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markClean(cfId, context.position);
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else if (context.segment > id)
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markClean(cfId, Integer.MAX_VALUE);
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}
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private void markClean(UUID cfId, int position)
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{
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ensureAtleast(cfClean, cfId, position);
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removeCleanFromDirty();
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}
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private static void ensureAtleast(ConcurrentMap<UUID, AtomicInteger> map, UUID cfId, int value)
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{
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AtomicInteger i = map.get(cfId);
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if (i == null)
|
||||
{
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AtomicInteger i2 = map.putIfAbsent(cfId, i = new AtomicInteger());
|
||||
if (i2 != null)
|
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i = i2;
|
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}
|
||||
while (true)
|
||||
{
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int cur = i.get();
|
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if (cur > value)
|
||||
break;
|
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if (i.compareAndSet(cur, value))
|
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break;
|
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}
|
||||
}
|
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|
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private void removeCleanFromDirty()
|
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{
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// if we're still allocating from this segment, don't touch anything since it can't be done thread-safely
|
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if (isStillAllocating())
|
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return;
|
||||
|
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Iterator<Map.Entry<UUID, AtomicInteger>> iter = cfClean.entrySet().iterator();
|
||||
while (iter.hasNext())
|
||||
{
|
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Map.Entry<UUID, AtomicInteger> clean = iter.next();
|
||||
UUID cfId = clean.getKey();
|
||||
AtomicInteger cleanPos = clean.getValue();
|
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AtomicInteger dirtyPos = cfDirty.get(cfId);
|
||||
if (dirtyPos != null && dirtyPos.intValue() <= cleanPos.intValue())
|
||||
{
|
||||
cfDirty.remove(cfId);
|
||||
iter.remove();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* @return a collection of dirty CFIDs for this segment file.
|
||||
*/
|
||||
public synchronized Collection<UUID> getDirtyCFIDs()
|
||||
{
|
||||
if (cfClean.isEmpty() || cfDirty.isEmpty())
|
||||
return cfDirty.keySet();
|
||||
|
||||
List<UUID> r = new ArrayList<>(cfDirty.size());
|
||||
for (Map.Entry<UUID, AtomicInteger> dirty : cfDirty.entrySet())
|
||||
{
|
||||
UUID cfId = dirty.getKey();
|
||||
AtomicInteger dirtyPos = dirty.getValue();
|
||||
AtomicInteger cleanPos = cfClean.get(cfId);
|
||||
if (cleanPos == null || cleanPos.intValue() < dirtyPos.intValue())
|
||||
r.add(dirty.getKey());
|
||||
}
|
||||
return r;
|
||||
}
|
||||
|
||||
/**
|
||||
* @return true if this segment is unused and safe to recycle or delete
|
||||
*/
|
||||
public synchronized boolean isUnused()
|
||||
{
|
||||
// if room to allocate, we're still in use as the active allocatingFrom,
|
||||
// so we don't want to race with updates to cfClean with removeCleanFromDirty
|
||||
if (isStillAllocating())
|
||||
return false;
|
||||
|
||||
removeCleanFromDirty();
|
||||
return cfDirty.isEmpty();
|
||||
}
|
||||
|
||||
/**
|
||||
* Check to see if a certain ReplayPosition is contained by this segment file.
|
||||
*
|
||||
* @param context the replay position to be checked
|
||||
* @return true if the replay position is contained by this segment file.
|
||||
*/
|
||||
public boolean contains(ReplayPosition context)
|
||||
{
|
||||
return context.segment == id;
|
||||
}
|
||||
|
||||
// For debugging, not fast
|
||||
public String dirtyString()
|
||||
{
|
||||
StringBuilder sb = new StringBuilder();
|
||||
for (UUID cfId : getDirtyCFIDs())
|
||||
{
|
||||
CFMetaData m = Schema.instance.getCFMetaData(cfId);
|
||||
sb.append(m == null ? "<deleted>" : m.cfName).append(" (").append(cfId).append("), ");
|
||||
}
|
||||
return sb.toString();
|
||||
}
|
||||
|
||||
@Override
|
||||
public String toString()
|
||||
{
|
||||
return "CommitLogSegment(" + getPath() + ')';
|
||||
}
|
||||
|
||||
public static class CommitLogSegmentFileComparator implements Comparator<File>
|
||||
{
|
||||
public int compare(File f, File f2)
|
||||
{
|
||||
CommitLogDescriptor desc = CommitLogDescriptor.fromFileName(f.getName());
|
||||
CommitLogDescriptor desc2 = CommitLogDescriptor.fromFileName(f2.getName());
|
||||
return Long.compare(desc.id, desc2.id);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* A simple class for tracking information about the portion of a segment that has been allocated to a log write.
|
||||
* The constructor leaves the fields uninitialized for population by CommitlogManager, so that it can be
|
||||
* stack-allocated by escape analysis in CommitLog.add.
|
||||
*/
|
||||
static class Allocation
|
||||
{
|
||||
|
||||
private final CommitLogSegment segment;
|
||||
private final OpOrder.Group appendOp;
|
||||
private final int position;
|
||||
private final ByteBuffer buffer;
|
||||
|
||||
Allocation(CommitLogSegment segment, OpOrder.Group appendOp, int position, ByteBuffer buffer)
|
||||
{
|
||||
this.segment = segment;
|
||||
this.appendOp = appendOp;
|
||||
this.position = position;
|
||||
this.buffer = buffer;
|
||||
}
|
||||
|
||||
CommitLogSegment getSegment()
|
||||
{
|
||||
return segment;
|
||||
}
|
||||
|
||||
ByteBuffer getBuffer()
|
||||
{
|
||||
return buffer;
|
||||
}
|
||||
|
||||
// markWritten() MUST be called once we are done with the segment or the CL will never flush
|
||||
// but must not be called more than once
|
||||
void markWritten()
|
||||
{
|
||||
appendOp.close();
|
||||
}
|
||||
|
||||
void awaitDiskSync()
|
||||
{
|
||||
while (segment.lastSyncedOffset < position)
|
||||
{
|
||||
WaitQueue.Signal signal = segment.syncComplete.register(CommitLog.instance.metrics.waitingOnCommit.time());
|
||||
if (segment.lastSyncedOffset < position)
|
||||
signal.awaitUninterruptibly();
|
||||
else
|
||||
signal.cancel();
|
||||
}
|
||||
}
|
||||
|
||||
public ReplayPosition getReplayPosition()
|
||||
{
|
||||
return new ReplayPosition(segment.id, buffer.limit());
|
||||
}
|
||||
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user