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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
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.InputStreamDataInput;
import org.apache.lucene.store.OutputStreamDataOutput;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.common.io.Channels;
import org.elasticsearch.common.io.stream.InputStreamStreamInput;
import org.elasticsearch.common.io.stream.OutputStreamStreamOutput;
import org.elasticsearch.common.io.stream.StreamInput;
import java.io.EOFException;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import static org.elasticsearch.index.seqno.SequenceNumbers.UNASSIGNED_PRIMARY_TERM;
/**
* Each translog file is started with a translog header then followed by translog operations.
*/
final class TranslogHeader {
public static final String TRANSLOG_CODEC = "translog";
public static final int VERSION_CHECKSUMS = 1; // pre-2.0 - unsupported
public static final int VERSION_CHECKPOINTS = 2; // added checkpoints
public static final int VERSION_PRIMARY_TERM = 3; // added primary term
public static final int CURRENT_VERSION = VERSION_PRIMARY_TERM;
private final String translogUUID;
private final long primaryTerm;
private final int headerSizeInBytes;
/**
* Creates a new translog header with the given uuid and primary term.
*
* @param translogUUID this UUID is used to prevent accidental recovery from a transaction log that belongs to a
* different engine
* @param primaryTerm the primary term of the owning index shard when creating (eg. rolling) this translog file.
* All operations' terms in this translog file are enforced to be at most this term.
*/
TranslogHeader(String translogUUID, long primaryTerm) {
this(translogUUID, primaryTerm, headerSizeInBytes(translogUUID));
assert primaryTerm >= 0 : "Primary term must be non-negative; term [" + primaryTerm + "]";
}
private TranslogHeader(String translogUUID, long primaryTerm, int headerSizeInBytes) {
this.translogUUID = translogUUID;
this.primaryTerm = primaryTerm;
this.headerSizeInBytes = headerSizeInBytes;
}
public String getTranslogUUID() {
return translogUUID;
}
/**
* Returns the primary term stored in this translog header.
* All operations in a translog file are expected to have their primary terms at most this term.
*/
public long getPrimaryTerm() {
return primaryTerm;
}
/**
* Returns the header size in bytes. This value can be used as the offset of the first translog operation.
* See {@link BaseTranslogReader#getFirstOperationOffset()}
*/
public int sizeInBytes() {
return headerSizeInBytes;
}
static int headerSizeInBytes(String translogUUID) {
return headerSizeInBytes(CURRENT_VERSION, new BytesRef(translogUUID).length);
}
private static int headerSizeInBytes(int version, int uuidLength) {
int size = CodecUtil.headerLength(TRANSLOG_CODEC);
size += Integer.BYTES + uuidLength; // uuid
if (version >= VERSION_PRIMARY_TERM) {
size += Long.BYTES; // primary term
size += Integer.BYTES; // checksum
}
return size;
}
static int readHeaderVersion(final Path path, final FileChannel channel, final StreamInput in) throws IOException {
final int version;
try {
version = CodecUtil.checkHeader(new InputStreamDataInput(in), TRANSLOG_CODEC, VERSION_CHECKSUMS, VERSION_PRIMARY_TERM);
} catch (CorruptIndexException | IndexFormatTooOldException | IndexFormatTooNewException e) {
tryReportOldVersionError(path, channel);
throw new TranslogCorruptedException(path.toString(), "translog header corrupted", e);
}
if (version == VERSION_CHECKSUMS) {
throw new IllegalStateException("pre-2.0 translog found [" + path + "]");
}
return version;
}
/**
* Read a translog header from the given path and file channel
*/
static TranslogHeader read(final String translogUUID, final Path path, final FileChannel channel) throws IOException {
try {
// This input is intentionally not closed because closing it will close the FileChannel.
final BufferedChecksumStreamInput in = new BufferedChecksumStreamInput(
new InputStreamStreamInput(java.nio.channels.Channels.newInputStream(channel), channel.size()),
path.toString()
);
final int version = readHeaderVersion(path, channel, in);
// Read the translogUUID
final int uuidLen = in.readInt();
if (uuidLen > channel.size()) {
throw new TranslogCorruptedException(path.toString(), "UUID length can't be larger than the translog");
}
if (uuidLen <= 0) {
throw new TranslogCorruptedException(path.toString(), "UUID length must be positive");
}
final BytesRef uuid = new BytesRef(uuidLen);
uuid.length = uuidLen;
in.read(uuid.bytes, uuid.offset, uuid.length);
// Read the primary term
final long primaryTerm;
if (version == VERSION_PRIMARY_TERM) {
primaryTerm = in.readLong();
} else {
assert version == VERSION_CHECKPOINTS : "Unknown header version [" + version + "]";
primaryTerm = UNASSIGNED_PRIMARY_TERM;
}
// Verify the checksum
if (version >= VERSION_PRIMARY_TERM) {
Translog.verifyChecksum(in);
}
assert primaryTerm >= 0 : "Primary term must be non-negative [" + primaryTerm + "]; translog path [" + path + "]";
final int headerSizeInBytes = headerSizeInBytes(version, uuid.length);
assert channel.position() == headerSizeInBytes
: "Header is not fully read; header size [" + headerSizeInBytes + "], position [" + channel.position() + "]";
// verify UUID only after checksum, to ensure that UUID is not corrupted
final BytesRef expectedUUID = new BytesRef(translogUUID);
if (uuid.bytesEquals(expectedUUID) == false) {
throw new TranslogCorruptedException(
path.toString(),
"expected shard UUID " + expectedUUID + " but got: " + uuid + " this translog file belongs to a different translog"
);
}
return new TranslogHeader(translogUUID, primaryTerm, headerSizeInBytes);
} catch (EOFException e) {
throw new TranslogCorruptedException(path.toString(), "translog header truncated", e);
}
}
private static void tryReportOldVersionError(final Path path, final FileChannel channel) throws IOException {
// 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
final byte b1 = Channels.readFromFileChannel(channel, 0, 1)[0];
if (b1 == 0x3f) { // LUCENE_CODEC_HEADER_BYTE
throw new TranslogCorruptedException(path.toString(), "translog looks like version 1 or later, but has corrupted header");
} else if (b1 == 0x00) { // UNVERSIONED_TRANSLOG_HEADER_BYTE
throw new IllegalStateException("pre-1.4 translog found [" + path + "]");
}
}
/**
* Writes this header with the latest format into the file channel
*/
void write(final FileChannel channel) throws IOException {
// This output is intentionally not closed because closing it will close the FileChannel.
@SuppressWarnings({ "IOResourceOpenedButNotSafelyClosed", "resource" })
final BufferedChecksumStreamOutput out = new BufferedChecksumStreamOutput(
new OutputStreamStreamOutput(java.nio.channels.Channels.newOutputStream(channel))
);
CodecUtil.writeHeader(new OutputStreamDataOutput(out), TRANSLOG_CODEC, CURRENT_VERSION);
// Write uuid
final BytesRef uuid = new BytesRef(translogUUID);
out.writeInt(uuid.length);
out.writeBytes(uuid.bytes, uuid.offset, uuid.length);
// Write primary term
out.writeLong(primaryTerm);
// Checksum header
out.writeInt((int) out.getChecksum());
out.flush();
channel.force(true);
assert channel.position() == headerSizeInBytes
: "Header is not fully written; header size [" + headerSizeInBytes + "], channel position [" + channel.position() + "]";
}
}
