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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.index.translog;
import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.IndexFormatTooNewException;
import org.apache.lucene.index.IndexFormatTooOldException;
import org.apache.lucene.store.AlreadyClosedException;
import org.apache.lucene.store.InputStreamDataInput;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.RamUsageEstimator;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.common.io.stream.ByteBufferStreamInput;
import org.elasticsearch.common.io.stream.InputStreamStreamInput;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A base class for all classes that allows reading ops from translog files
*/
public abstract class TranslogReader implements Closeable, Comparable {
public static final int UNKNOWN_OP_COUNT = -1;
private static final byte LUCENE_CODEC_HEADER_BYTE = 0x3f;
private static final byte UNVERSIONED_TRANSLOG_HEADER_BYTE = 0x00;
protected final long generation;
protected final ChannelReference channelReference;
protected final FileChannel channel;
protected final AtomicBoolean closed = new AtomicBoolean(false);
protected final long firstOperationOffset;
public TranslogReader(long generation, ChannelReference channelReference, long firstOperationOffset) {
this.generation = generation;
this.channelReference = channelReference;
this.channel = channelReference.getChannel();
this.firstOperationOffset = firstOperationOffset;
}
public long getGeneration() {
return this.generation;
}
public abstract long sizeInBytes();
abstract public int totalOperations();
public final long getFirstOperationOffset() {
return firstOperationOffset;
}
public Translog.Operation read(Translog.Location location) throws IOException {
assert location.generation == generation : "read location's translog generation [" + location.generation + "] is not [" + generation + "]";
ByteBuffer buffer = ByteBuffer.allocate(location.size);
try (BufferedChecksumStreamInput checksumStreamInput = checksummedStream(buffer, location.translogLocation, location.size, null)) {
return read(checksumStreamInput);
}
}
/** read the size of the op (i.e., number of bytes, including the op size) written at the given position */
private final int readSize(ByteBuffer reusableBuffer, long position) {
// read op size from disk
assert reusableBuffer.capacity() >= 4 : "reusable buffer must have capacity >=4 when reading opSize. got [" + reusableBuffer.capacity() + "]";
try {
reusableBuffer.clear();
reusableBuffer.limit(4);
readBytes(reusableBuffer, position);
reusableBuffer.flip();
// Add an extra 4 to account for the operation size integer itself
final int size = reusableBuffer.getInt() + 4;
final long maxSize = sizeInBytes() - position;
if (size < 0 || size > maxSize) {
throw new TranslogCorruptedException("operation size is corrupted must be [0.." + maxSize + "] but was: " + size);
}
return size;
} catch (IOException e) {
throw new ElasticsearchException("unexpected exception reading from translog snapshot of " + this.channelReference.getPath(), e);
}
}
public Translog.Snapshot newSnapshot() {
final ByteBuffer reusableBuffer = ByteBuffer.allocate(1024);
final int totalOperations = totalOperations();
channelReference.incRef();
return newReaderSnapshot(totalOperations, reusableBuffer);
}
/**
* reads an operation at the given position and returns it. The buffer length is equal to the number
* of bytes reads.
*/
private final BufferedChecksumStreamInput checksummedStream(ByteBuffer reusableBuffer, long position, int opSize, BufferedChecksumStreamInput reuse) throws IOException {
final ByteBuffer buffer;
if (reusableBuffer.capacity() >= opSize) {
buffer = reusableBuffer;
} else {
buffer = ByteBuffer.allocate(opSize);
}
buffer.clear();
buffer.limit(opSize);
readBytes(buffer, position);
buffer.flip();
return new BufferedChecksumStreamInput(new ByteBufferStreamInput(buffer), reuse);
}
protected Translog.Operation read(BufferedChecksumStreamInput inStream) throws IOException {
return Translog.readOperation(inStream);
}
/**
* reads bytes at position into the given buffer, filling it.
*/
abstract protected void readBytes(ByteBuffer buffer, long position) throws IOException;
@Override
public final void close() throws IOException {
if (closed.compareAndSet(false, true)) {
channelReference.decRef();
}
}
protected final boolean isClosed() {
return closed.get();
}
protected void ensureOpen() {
if (isClosed()) {
throw new AlreadyClosedException("translog [" + getGeneration() + "] is already closed");
}
}
@Override
public String toString() {
return "translog [" + generation + "][" + channelReference.getPath() + "]";
}
@Override
public int compareTo(TranslogReader o) {
return Long.compare(getGeneration(), o.getGeneration());
}
/**
* Given a file, return a VersionedTranslogStream based on an
* optionally-existing header in the file. If the file does not exist, or
* has zero length, returns the latest version. If the header does not
* exist, assumes Version 0 of the translog file format.
*/
public static ImmutableTranslogReader open(ChannelReference channelReference, Checkpoint checkpoint, String translogUUID) throws IOException {
final FileChannel channel = channelReference.getChannel();
final Path path = channelReference.getPath();
assert channelReference.getGeneration() == checkpoint.generation : "expected generation: " + channelReference.getGeneration() + " but got: " + checkpoint.generation;
try {
if (checkpoint.offset == 0 && checkpoint.numOps == TranslogReader.UNKNOWN_OP_COUNT) { // only old files can be empty
return new LegacyTranslogReader(channelReference.getGeneration(), channelReference, 0);
}
InputStreamStreamInput headerStream = new InputStreamStreamInput(Channels.newInputStream(channel)); // don't close
// Lucene's CodecUtil writes a magic number of 0x3FD76C17 with the
// header, in binary this looks like:
//
// binary: 0011 1111 1101 0111 0110 1100 0001 0111
// hex : 3 f d 7 6 c 1 7
//
// With version 0 of the translog, the first byte is the
// Operation.Type, which will always be between 0-4, so we know if
// we grab the first byte, it can be:
// 0x3f => Lucene's magic number, so we can assume it's version 1 or later
// 0x00 => version 0 of the translog
//
// otherwise the first byte of the translog is corrupted and we
// should bail
byte b1 = headerStream.readByte();
if (b1 == LUCENE_CODEC_HEADER_BYTE) {
// Read 3 more bytes, meaning a whole integer has been read
byte b2 = headerStream.readByte();
byte b3 = headerStream.readByte();
byte b4 = headerStream.readByte();
// Convert the 4 bytes that were read into an integer
int header = ((b1 & 0xFF) << 24) + ((b2 & 0xFF) << 16) + ((b3 & 0xFF) << 8) + ((b4 & 0xFF) << 0);
// We confirm CodecUtil's CODEC_MAGIC number (0x3FD76C17)
// ourselves here, because it allows us to read the first
// byte separately
if (header != CodecUtil.CODEC_MAGIC) {
throw new TranslogCorruptedException("translog looks like version 1 or later, but has corrupted header");
}
// Confirm the rest of the header using CodecUtil, extracting
// the translog version
int version = CodecUtil.checkHeaderNoMagic(new InputStreamDataInput(headerStream), TranslogWriter.TRANSLOG_CODEC, 1, Integer.MAX_VALUE);
switch (version) {
case TranslogWriter.VERSION_CHECKSUMS:
assert checkpoint.numOps == TranslogReader.UNKNOWN_OP_COUNT : "expected unknown op count but got: " + checkpoint.numOps;
assert checkpoint.offset == Files.size(path) : "offset(" + checkpoint.offset + ") != file_size(" + Files.size(path) + ") for: " + path;
// legacy - we still have to support it somehow
return new LegacyTranslogReaderBase(channelReference.getGeneration(), channelReference, CodecUtil.headerLength(TranslogWriter.TRANSLOG_CODEC), checkpoint.offset);
case TranslogWriter.VERSION_CHECKPOINTS:
assert path.getFileName().toString().endsWith(Translog.TRANSLOG_FILE_SUFFIX) : "new file ends with old suffix: " + path;
assert checkpoint.numOps > TranslogReader.UNKNOWN_OP_COUNT: "expected at least 0 operatin but got: " + checkpoint.numOps;
assert checkpoint.offset <= channel.size() : "checkpoint is inconsistent with channel length: " + channel.size() + " " + checkpoint;
int len = headerStream.readInt();
if (len > channel.size()) {
throw new TranslogCorruptedException("uuid length can't be larger than the translog");
}
BytesRef ref = new BytesRef(len);
ref.length = len;
headerStream.read(ref.bytes, ref.offset, ref.length);
BytesRef uuidBytes = new BytesRef(translogUUID);
if (uuidBytes.bytesEquals(ref) == false) {
throw new TranslogCorruptedException("expected shard UUID [" + uuidBytes + "] but got: [" + ref + "] this translog file belongs to a different translog");
}
return new ImmutableTranslogReader(channelReference.getGeneration(), channelReference, ref.length + CodecUtil.headerLength(TranslogWriter.TRANSLOG_CODEC) + RamUsageEstimator.NUM_BYTES_INT, checkpoint.offset, checkpoint.numOps);
default:
throw new TranslogCorruptedException("No known translog stream version: " + version + " path:" + path);
}
} else if (b1 == UNVERSIONED_TRANSLOG_HEADER_BYTE) {
assert checkpoint.numOps == TranslogReader.UNKNOWN_OP_COUNT : "expected unknown op count but got: " + checkpoint.numOps;
assert checkpoint.offset == Files.size(path) : "offset(" + checkpoint.offset + ") != file_size(" + Files.size(path) + ") for: " + path;
return new LegacyTranslogReader(channelReference.getGeneration(), channelReference, checkpoint.offset);
} else {
throw new TranslogCorruptedException("Invalid first byte in translog file, got: " + Long.toHexString(b1) + ", expected 0x00 or 0x3f");
}
} catch (CorruptIndexException | IndexFormatTooOldException | IndexFormatTooNewException e) {
throw new TranslogCorruptedException("Translog header corrupted", e);
}
}
public Path path() {
return channelReference.getPath();
}
protected Translog.Snapshot newReaderSnapshot(int totalOperations, ByteBuffer reusableBuffer) {
return new ReaderSnapshot(totalOperations, reusableBuffer);
}
class ReaderSnapshot implements Translog.Snapshot {
private final AtomicBoolean closed;
private final int totalOperations;
private final ByteBuffer reusableBuffer;
long position;
int readOperations;
private BufferedChecksumStreamInput reuse;
public ReaderSnapshot(int totalOperations, ByteBuffer reusableBuffer) {
this.totalOperations = totalOperations;
this.reusableBuffer = reusableBuffer;
closed = new AtomicBoolean(false);
position = firstOperationOffset;
readOperations = 0;
reuse = null;
}
@Override
public final int estimatedTotalOperations() {
return totalOperations;
}
@Override
public Translog.Operation next() throws IOException {
if (readOperations < totalOperations) {
assert readOperations < totalOperations : "readOpeartions must be less than totalOperations";
return readOperation();
} else {
return null;
}
}
protected final Translog.Operation readOperation() throws IOException {
final int opSize = readSize(reusableBuffer, position);
reuse = checksummedStream(reusableBuffer, position, opSize, reuse);
Translog.Operation op = read(reuse);
position += opSize;
readOperations++;
return op;
}
@Override
public void close() {
if (closed.compareAndSet(false, true)) {
channelReference.decRef();
}
}
}
}