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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
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*/
package org.elasticsearch.index.translog;
import org.apache.logging.log4j.message.ParameterizedMessage;
import org.apache.logging.log4j.util.Supplier;
import org.apache.lucene.index.Term;
import org.apache.lucene.store.AlreadyClosedException;
import org.apache.lucene.util.IOUtils;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.common.UUIDs;
import org.elasticsearch.common.bytes.BytesArray;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.bytes.ReleasablePagedBytesReference;
import org.elasticsearch.common.io.stream.ReleasableBytesStreamOutput;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.lease.Releasable;
import org.elasticsearch.common.lease.Releasables;
import org.elasticsearch.common.lucene.uid.Versions;
import org.elasticsearch.common.util.BigArrays;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
import org.elasticsearch.common.util.concurrent.ReleasableLock;
import org.elasticsearch.index.VersionType;
import org.elasticsearch.index.engine.Engine;
import org.elasticsearch.index.seqno.SequenceNumbersService;
import org.elasticsearch.index.shard.AbstractIndexShardComponent;
import org.elasticsearch.index.shard.IndexShardComponent;
import java.io.Closeable;
import java.io.EOFException;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.LongSupplier;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* A Translog is a per index shard component that records all non-committed index operations in a durable manner.
* In Elasticsearch there is one Translog instance per {@link org.elasticsearch.index.engine.InternalEngine}. The engine
* records the current translog generation {@link Translog#getGeneration()} in it's commit metadata using {@link #TRANSLOG_GENERATION_KEY}
* to reference the generation that contains all operations that have not yet successfully been committed to the engines lucene index.
* Additionally, since Elasticsearch 2.0 the engine also records a {@link #TRANSLOG_UUID_KEY} with each commit to ensure a strong association
* between the lucene index an the transaction log file. This UUID is used to prevent accidental recovery from a transaction log that belongs to a
* different engine.
* <p>
* Each Translog has only one translog file open at any time referenced by a translog generation ID. This ID is written to a <tt>translog.ckp</tt> file that is designed
* to fit in a single disk block such that a write of the file is atomic. The checkpoint file is written on each fsync operation of the translog and records the number of operations
* written, the current translogs file generation and it's fsynced offset in bytes.
* </p>
* <p>
* When a translog is opened the checkpoint is use to retrieve the latest translog file generation and subsequently to open the last written file to recovery operations.
* The {@link org.elasticsearch.index.translog.Translog.TranslogGeneration}, given when the translog is opened / constructed is compared against
* the latest generation and all consecutive translog files singe the given generation and the last generation in the checkpoint will be recovered and preserved until the next
* generation is committed using {@link Translog#commit(long)}. In the common case the translog file generation in the checkpoint and the generation passed to the translog on creation are
* the same. The only situation when they can be different is when an actual translog commit fails in between {@link Translog#prepareCommit()} and {@link Translog#commit(long)}. In such a case
* the currently being committed translog file will not be deleted since it's commit was not successful. Yet, a new/current translog file is already opened at that point such that there is more than
* one translog file present. Such an uncommitted translog file always has a <tt>translog-${gen}.ckp</tt> associated with it which is an fsynced copy of the it's last <tt>translog.ckp</tt> such that in
* disaster recovery last fsynced offsets, number of operation etc. are still preserved.
* </p>
*/
public class Translog extends AbstractIndexShardComponent implements IndexShardComponent, Closeable {
/*
* TODO
* - we might need something like a deletion policy to hold on to more than one translog eventually (I think sequence IDs needs this) but we can refactor as we go
* - use a simple BufferedOutputStream to write stuff and fold BufferedTranslogWriter into it's super class... the tricky bit is we need to be able to do random access reads even from the buffer
* - we need random exception on the FileSystem API tests for all this.
* - we need to page align the last write before we sync, we can take advantage of ensureSynced for this since we might have already fsynced far enough
*/
public static final String TRANSLOG_GENERATION_KEY = "translog_generation";
public static final String TRANSLOG_UUID_KEY = "translog_uuid";
public static final String TRANSLOG_FILE_PREFIX = "translog-";
public static final String TRANSLOG_FILE_SUFFIX = ".tlog";
public static final String CHECKPOINT_SUFFIX = ".ckp";
public static final String CHECKPOINT_FILE_NAME = "translog" + CHECKPOINT_SUFFIX;
static final Pattern PARSE_STRICT_ID_PATTERN = Pattern.compile("^" + TRANSLOG_FILE_PREFIX + "(\\d+)(\\.tlog)$");
// the list of translog readers is guaranteed to be in order of translog generation
private final List<TranslogReader> readers = new ArrayList<>();
// this is a concurrent set and is not protected by any of the locks. The main reason
// is that is being accessed by two separate classes (additions & reading are done by Translog, remove by View when closed)
private final Set<View> outstandingViews = ConcurrentCollections.newConcurrentSet();
private BigArrays bigArrays;
protected final ReleasableLock readLock;
protected final ReleasableLock writeLock;
private final Path location;
private TranslogWriter current;
private static final long NOT_SET_GENERATION = -1; // -1 is safe as it will not cause a translog deletion.
private volatile long currentCommittingGeneration = NOT_SET_GENERATION;
private volatile long lastCommittedTranslogFileGeneration = NOT_SET_GENERATION;
private final AtomicBoolean closed = new AtomicBoolean();
private final TranslogConfig config;
private final LongSupplier globalCheckpointSupplier;
private final String translogUUID;
/**
* Creates a new Translog instance. This method will create a new transaction log unless the given {@link TranslogGeneration} is
* {@code null}. If the generation is {@code null} this method is destructive and will delete all files in the translog path given. If
* the generation is not {@code null}, this method tries to open the given translog generation. The generation is treated as the last
* generation referenced from already committed data. This means all operations that have not yet been committed should be in the
* translog file referenced by this generation. The translog creation will fail if this generation can't be opened.
*
* @param config the configuration of this translog
* @param translogGeneration the translog generation to open
* @param globalCheckpointSupplier a supplier for the global checkpoint
*/
public Translog(
final TranslogConfig config,
final TranslogGeneration translogGeneration,
final LongSupplier globalCheckpointSupplier) throws IOException {
super(config.getShardId(), config.getIndexSettings());
this.config = config;
this.globalCheckpointSupplier = globalCheckpointSupplier;
if (translogGeneration == null || translogGeneration.translogUUID == null) { // legacy case
translogUUID = UUIDs.randomBase64UUID();
} else {
translogUUID = translogGeneration.translogUUID;
}
bigArrays = config.getBigArrays();
ReadWriteLock rwl = new ReentrantReadWriteLock();
readLock = new ReleasableLock(rwl.readLock());
writeLock = new ReleasableLock(rwl.writeLock());
this.location = config.getTranslogPath();
Files.createDirectories(this.location);
try {
if (translogGeneration != null) {
final Checkpoint checkpoint = readCheckpoint(location);
final Path nextTranslogFile = location.resolve(getFilename(checkpoint.generation + 1));
final Path currentCheckpointFile = location.resolve(getCommitCheckpointFileName(checkpoint.generation));
// this is special handling for error condition when we create a new writer but we fail to bake
// the newly written file (generation+1) into the checkpoint. This is still a valid state
// we just need to cleanup before we continue
// we hit this before and then blindly deleted the new generation even though we managed to bake it in and then hit this:
// https://discuss.elastic.co/t/cannot-recover-index-because-of-missing-tanslog-files/38336 as an example
//
// For this to happen we must have already copied the translog.ckp file into translog-gen.ckp so we first check if that file exists
// if not we don't even try to clean it up and wait until we fail creating it
assert Files.exists(nextTranslogFile) == false || Files.size(nextTranslogFile) <= TranslogWriter.getHeaderLength(translogUUID) : "unexpected translog file: [" + nextTranslogFile + "]";
if (Files.exists(currentCheckpointFile) // current checkpoint is already copied
&& Files.deleteIfExists(nextTranslogFile)) { // delete it and log a warning
logger.warn("deleted previously created, but not yet committed, next generation [{}]. This can happen due to a tragic exception when creating a new generation", nextTranslogFile.getFileName());
}
this.readers.addAll(recoverFromFiles(translogGeneration, checkpoint));
if (readers.isEmpty()) {
throw new IllegalStateException("at least one reader must be recovered");
}
boolean success = false;
try {
current = createWriter(checkpoint.generation + 1);
this.lastCommittedTranslogFileGeneration = translogGeneration.translogFileGeneration;
success = true;
} finally {
// we have to close all the recovered ones otherwise we leak file handles here
// for instance if we have a lot of tlog and we can't create the writer we keep on holding
// on to all the uncommitted tlog files if we don't close
if (success == false) {
IOUtils.closeWhileHandlingException(readers);
}
}
} else {
IOUtils.rm(location);
logger.debug("wipe translog location - creating new translog");
Files.createDirectories(location);
final long generation = 1;
final Checkpoint checkpoint = Checkpoint.emptyTranslogCheckpoint(0, generation, globalCheckpointSupplier.getAsLong());
final Path checkpointFile = location.resolve(CHECKPOINT_FILE_NAME);
Checkpoint.write(getChannelFactory(), checkpointFile, checkpoint, StandardOpenOption.WRITE, StandardOpenOption.CREATE_NEW);
IOUtils.fsync(checkpointFile, false);
current = createWriter(generation);
this.lastCommittedTranslogFileGeneration = NOT_SET_GENERATION;
}
// now that we know which files are there, create a new current one.
} catch (Exception e) {
// close the opened translog files if we fail to create a new translog...
IOUtils.closeWhileHandlingException(current);
IOUtils.closeWhileHandlingException(readers);
throw e;
}
}
/** recover all translog files found on disk */
private ArrayList<TranslogReader> recoverFromFiles(TranslogGeneration translogGeneration, Checkpoint checkpoint) throws IOException {
boolean success = false;
ArrayList<TranslogReader> foundTranslogs = new ArrayList<>();
final Path tempFile = Files.createTempFile(location, TRANSLOG_FILE_PREFIX, TRANSLOG_FILE_SUFFIX); // a temp file to copy checkpoint to - note it must be in on the same FS otherwise atomic move won't work
boolean tempFileRenamed = false;
try (ReleasableLock lock = writeLock.acquire()) {
logger.debug("open uncommitted translog checkpoint {}", checkpoint);
final String checkpointTranslogFile = getFilename(checkpoint.generation);
for (long i = translogGeneration.translogFileGeneration; i < checkpoint.generation; i++) {
Path committedTranslogFile = location.resolve(getFilename(i));
if (Files.exists(committedTranslogFile) == false) {
throw new IllegalStateException("translog file doesn't exist with generation: " + i + " lastCommitted: " + lastCommittedTranslogFileGeneration + " checkpoint: " + checkpoint.generation + " - translog ids must be consecutive");
}
final TranslogReader reader = openReader(committedTranslogFile, Checkpoint.read(location.resolve(getCommitCheckpointFileName(i))));
foundTranslogs.add(reader);
logger.debug("recovered local translog from checkpoint {}", checkpoint);
}
foundTranslogs.add(openReader(location.resolve(checkpointTranslogFile), checkpoint));
Path commitCheckpoint = location.resolve(getCommitCheckpointFileName(checkpoint.generation));
if (Files.exists(commitCheckpoint)) {
Checkpoint checkpointFromDisk = Checkpoint.read(commitCheckpoint);
if (checkpoint.equals(checkpointFromDisk) == false) {
throw new IllegalStateException("Checkpoint file " + commitCheckpoint.getFileName() + " already exists but has corrupted content expected: " + checkpoint + " but got: " + checkpointFromDisk);
}
} else {
// we first copy this into the temp-file and then fsync it followed by an atomic move into the target file
// that way if we hit a disk-full here we are still in an consistent state.
Files.copy(location.resolve(CHECKPOINT_FILE_NAME), tempFile, StandardCopyOption.REPLACE_EXISTING);
IOUtils.fsync(tempFile, false);
Files.move(tempFile, commitCheckpoint, StandardCopyOption.ATOMIC_MOVE);
tempFileRenamed = true;
// we only fsync the directory the tempFile was already fsynced
IOUtils.fsync(commitCheckpoint.getParent(), true);
}
success = true;
} finally {
if (success == false) {
IOUtils.closeWhileHandlingException(foundTranslogs);
}
if (tempFileRenamed == false) {
try {
Files.delete(tempFile);
} catch (IOException ex) {
logger.warn((Supplier<?>) () -> new ParameterizedMessage("failed to delete temp file {}", tempFile), ex);
}
}
}
return foundTranslogs;
}
TranslogReader openReader(Path path, Checkpoint checkpoint) throws IOException {
FileChannel channel = FileChannel.open(path, StandardOpenOption.READ);
try {
assert Translog.parseIdFromFileName(path) == checkpoint.generation : "expected generation: " + Translog.parseIdFromFileName(path) + " but got: " + checkpoint.generation;
TranslogReader reader = TranslogReader.open(channel, path, checkpoint, translogUUID);
channel = null;
return reader;
} finally {
IOUtils.close(channel);
}
}
/**
* Extracts the translog generation from a file name.
*
* @throws IllegalArgumentException if the path doesn't match the expected pattern.
*/
public static long parseIdFromFileName(Path translogFile) {
final String fileName = translogFile.getFileName().toString();
final Matcher matcher = PARSE_STRICT_ID_PATTERN.matcher(fileName);
if (matcher.matches()) {
try {
return Long.parseLong(matcher.group(1));
} catch (NumberFormatException e) {
throw new IllegalStateException("number formatting issue in a file that passed PARSE_STRICT_ID_PATTERN: " + fileName + "]", e);
}
}
throw new IllegalArgumentException("can't parse id from file: " + fileName);
}
/** Returns {@code true} if this {@code Translog} is still open. */
public boolean isOpen() {
return closed.get() == false;
}
@Override
public void close() throws IOException {
if (closed.compareAndSet(false, true)) {
try (ReleasableLock lock = writeLock.acquire()) {
try {
current.sync();
} finally {
closeFilesIfNoPendingViews();
}
} finally {
logger.debug("translog closed");
}
}
}
/**
* Returns all translog locations as absolute paths.
* These paths don't contain actual translog files they are
* directories holding the transaction logs.
*/
public Path location() {
return location;
}
/**
* Returns the generation of the current transaction log.
*/
public long currentFileGeneration() {
try (ReleasableLock ignored = readLock.acquire()) {
return current.getGeneration();
}
}
/**
* Returns the number of operations in the transaction files that aren't committed to lucene..
*/
public int totalOperations() {
return totalOperations(lastCommittedTranslogFileGeneration);
}
/**
* Returns the size in bytes of the translog files that aren't committed to lucene.
*/
public long sizeInBytes() {
return sizeInBytes(lastCommittedTranslogFileGeneration);
}
/**
* Returns the number of operations in the transaction files that aren't committed to lucene..
*/
private int totalOperations(long minGeneration) {
try (ReleasableLock ignored = readLock.acquire()) {
ensureOpen();
return Stream.concat(readers.stream(), Stream.of(current))
.filter(r -> r.getGeneration() >= minGeneration)
.mapToInt(BaseTranslogReader::totalOperations)
.sum();
}
}
/**
* Returns the size in bytes of the translog files that aren't committed to lucene.
*/
private long sizeInBytes(long minGeneration) {
try (ReleasableLock ignored = readLock.acquire()) {
ensureOpen();
return Stream.concat(readers.stream(), Stream.of(current))
.filter(r -> r.getGeneration() >= minGeneration)
.mapToLong(BaseTranslogReader::sizeInBytes)
.sum();
}
}
/**
* Creates a new translog for the specified generation.
*
* @param fileGeneration the translog generation
* @return a writer for the new translog
* @throws IOException if creating the translog failed
*/
TranslogWriter createWriter(long fileGeneration) throws IOException {
final TranslogWriter newFile;
try {
newFile = TranslogWriter.create(
shardId,
translogUUID,
fileGeneration,
location.resolve(getFilename(fileGeneration)),
getChannelFactory(),
config.getBufferSize(),
globalCheckpointSupplier);
} catch (final IOException e) {
throw new TranslogException(shardId, "failed to create new translog file", e);
}
return newFile;
}
/**
* Adds an operation to the transaction log.
*
* @param operation the operation to add
* @return the location of the operation in the translog
* @throws IOException if adding the operation to the translog resulted in an I/O exception
*/
public Location add(final Operation operation) throws IOException {
final ReleasableBytesStreamOutput out = new ReleasableBytesStreamOutput(bigArrays);
try {
final long start = out.position();
out.skip(Integer.BYTES);
writeOperationNoSize(new BufferedChecksumStreamOutput(out), operation);
final long end = out.position();
final int operationSize = (int) (end - Integer.BYTES - start);
out.seek(start);
out.writeInt(operationSize);
out.seek(end);
final ReleasablePagedBytesReference bytes = out.bytes();
try (ReleasableLock ignored = readLock.acquire()) {
ensureOpen();
return current.add(bytes, operation.seqNo());
}
} catch (final AlreadyClosedException | IOException ex) {
try {
closeOnTragicEvent(ex);
} catch (final Exception inner) {
ex.addSuppressed(inner);
}
throw ex;
} catch (final Exception e) {
try {
closeOnTragicEvent(e);
} catch (final Exception inner) {
e.addSuppressed(inner);
}
throw new TranslogException(shardId, "Failed to write operation [" + operation + "]", e);
} finally {
Releasables.close(out);
}
}
/**
* Tests whether or not the translog should be flushed. This test is based on the current size
* of the translog comparted to the configured flush threshold size.
*
* @return {@code true} if the translog should be flushed
*/
public boolean shouldFlush() {
final long size = this.sizeInBytes();
return size > this.indexSettings.getFlushThresholdSize().getBytes();
}
/**
* Tests whether or not the translog generation should be rolled to a new generation. This test
* is based on the size of the current generation compared to the configured generation
* threshold size.
*
* @return {@code true} if the current generation should be rolled to a new generation
*/
public boolean shouldRollGeneration() {
final long size = this.current.sizeInBytes();
final long threshold = this.indexSettings.getGenerationThresholdSize().getBytes();
return size > threshold;
}
/**
* The a {@linkplain Location} that will sort after the {@linkplain Location} returned by the last write but before any locations which
* can be returned by the next write.
*/
public Location getLastWriteLocation() {
try (ReleasableLock lock = readLock.acquire()) {
/*
* We use position = current - 1 and size = Integer.MAX_VALUE here instead of position current and size = 0 for two reasons:
* 1. Translog.Location's compareTo doesn't actually pay attention to size even though it's equals method does.
* 2. It feels more right to return a *position* that is before the next write's position rather than rely on the size.
*/
return new Location(current.generation, current.sizeInBytes() - 1, Integer.MAX_VALUE);
}
}
/**
* The last synced checkpoint for this translog.
*
* @return the last synced checkpoint
*/
public long getLastSyncedGlobalCheckpoint() {
try (ReleasableLock ignored = readLock.acquire()) {
return current.getLastSyncedCheckpoint().globalCheckpoint;
}
}
/**
* Snapshots the current transaction log allowing to safely iterate over the snapshot.
* Snapshots are fixed in time and will not be updated with future operations.
*/
public Snapshot newSnapshot() {
return createSnapshot(Long.MIN_VALUE);
}
private Snapshot createSnapshot(long minGeneration) {
try (ReleasableLock ignored = readLock.acquire()) {
ensureOpen();
Snapshot[] snapshots = Stream.concat(readers.stream(), Stream.of(current))
.filter(reader -> reader.getGeneration() >= minGeneration)
.map(BaseTranslogReader::newSnapshot).toArray(Snapshot[]::new);
return new MultiSnapshot(snapshots);
}
}
/**
* Returns a view into the current translog that is guaranteed to retain all current operations
* while receiving future ones as well
*/
public Translog.View newView() {
try (ReleasableLock lock = readLock.acquire()) {
ensureOpen();
View view = new View(lastCommittedTranslogFileGeneration);
outstandingViews.add(view);
return view;
}
}
/**
* Sync's the translog.
*/
public void sync() throws IOException {
try (ReleasableLock lock = readLock.acquire()) {
if (closed.get() == false) {
current.sync();
}
} catch (Exception ex) {
try {
closeOnTragicEvent(ex);
} catch (Exception inner) {
ex.addSuppressed(inner);
}
throw ex;
}
}
/**
* Returns <code>true</code> if an fsync is required to ensure durability of the translogs operations or it's metadata.
*/
public boolean syncNeeded() {
try (ReleasableLock lock = readLock.acquire()) {
return current.syncNeeded();
}
}
/** package private for testing */
public static String getFilename(long generation) {
return TRANSLOG_FILE_PREFIX + generation + TRANSLOG_FILE_SUFFIX;
}
static String getCommitCheckpointFileName(long generation) {
return TRANSLOG_FILE_PREFIX + generation + CHECKPOINT_SUFFIX;
}
/**
* Ensures that the given location has be synced / written to the underlying storage.
*
* @return Returns <code>true</code> iff this call caused an actual sync operation otherwise <code>false</code>
*/
public boolean ensureSynced(Location location) throws IOException {
try (ReleasableLock lock = readLock.acquire()) {
if (location.generation == current.getGeneration()) { // if we have a new one it's already synced
ensureOpen();
return current.syncUpTo(location.translogLocation + location.size);
}
} catch (Exception ex) {
try {
closeOnTragicEvent(ex);
} catch (Exception inner) {
ex.addSuppressed(inner);
}
throw ex;
}
return false;
}
/**
* Ensures that all locations in the given stream have been synced / written to the underlying storage.
* This method allows for internal optimization to minimize the amount of fsync operations if multiple
* locations must be synced.
*
* @return Returns <code>true</code> iff this call caused an actual sync operation otherwise <code>false</code>
*/
public boolean ensureSynced(Stream<Location> locations) throws IOException {
final Optional<Location> max = locations.max(Location::compareTo);
// we only need to sync the max location since it will sync all other
// locations implicitly
if (max.isPresent()) {
return ensureSynced(max.get());
} else {
return false;
}
}
private void closeOnTragicEvent(Exception ex) {
if (current.getTragicException() != null) {
try {
close();
} catch (AlreadyClosedException inner) {
// don't do anything in this case. The AlreadyClosedException comes from TranslogWriter and we should not add it as suppressed because
// will contain the Exception ex as cause. See also https://github.com/elastic/elasticsearch/issues/15941
} catch (Exception inner) {
assert (ex != inner.getCause());
ex.addSuppressed(inner);
}
}
}
/**
* return stats
*/
public TranslogStats stats() {
// acquire lock to make the two numbers roughly consistent (no file change half way)
try (ReleasableLock lock = readLock.acquire()) {
return new TranslogStats(totalOperations(), sizeInBytes());
}
}
public TranslogConfig getConfig() {
return config;
}
/**
* a view into the translog, capturing all translog file at the moment of creation
* and updated with any future translog.
*/
/**
* a view into the translog, capturing all translog file at the moment of creation
* and updated with any future translog.
*/
public class View implements Closeable {
AtomicBoolean closed = new AtomicBoolean();
final long minGeneration;
View(long minGeneration) {
this.minGeneration = minGeneration;
}
/** this smallest translog generation in this view */
public long minTranslogGeneration() {
return minGeneration;
}
/**
* The total number of operations in the view.
*/
public int totalOperations() {
return Translog.this.totalOperations(minGeneration);
}
/**
* Returns the size in bytes of the files behind the view.
*/
public long sizeInBytes() {
return Translog.this.sizeInBytes(minGeneration);
}
/** create a snapshot from this view */
public Snapshot snapshot() {
ensureOpen();
return Translog.this.createSnapshot(minGeneration);
}
void ensureOpen() {
if (closed.get()) {
throw new AlreadyClosedException("View is already closed");
}
}
@Override
public void close() throws IOException {
if (closed.getAndSet(true) == false) {
logger.trace("closing view starting at translog [{}]", minTranslogGeneration());
boolean removed = outstandingViews.remove(this);
assert removed : "View was never set but was supposed to be removed";
trimUnreferencedReaders();
closeFilesIfNoPendingViews();
}
}
}
public static class Location implements Comparable<Location> {
public final long generation;
public final long translogLocation;
public final int size;
public Location(long generation, long translogLocation, int size) {
this.generation = generation;
this.translogLocation = translogLocation;
this.size = size;
}
public String toString() {
return "[generation: " + generation + ", location: " + translogLocation + ", size: " + size + "]";
}
@Override
public int compareTo(Location o) {
if (generation == o.generation) {
return Long.compare(translogLocation, o.translogLocation);
}
return Long.compare(generation, o.generation);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Location location = (Location) o;
if (generation != location.generation) {
return false;
}
if (translogLocation != location.translogLocation) {
return false;
}
return size == location.size;
}
@Override
public int hashCode() {
int result = Long.hashCode(generation);
result = 31 * result + Long.hashCode(translogLocation);
result = 31 * result + size;
return result;
}
}
/**
* A snapshot of the transaction log, allows to iterate over all the transaction log operations.
*/
public interface Snapshot {
/**
* The total number of operations in the translog.
*/
int totalOperations();
/**
* Returns the next operation in the snapshot or <code>null</code> if we reached the end.
*/
Translog.Operation next() throws IOException;
}
/**
* A generic interface representing an operation performed on the transaction log.
* Each is associated with a type.
*/
public interface Operation extends Writeable {
enum Type {
@Deprecated
CREATE((byte) 1),
INDEX((byte) 2),
DELETE((byte) 3),
NO_OP((byte) 4);
private final byte id;
Type(byte id) {
this.id = id;
}
public byte id() {
return this.id;
}
public static Type fromId(byte id) {
switch (id) {
case 1:
return CREATE;
case 2:
return INDEX;
case 3:
return DELETE;
case 4:
return NO_OP;
default:
throw new IllegalArgumentException("No type mapped for [" + id + "]");
}
}
}
Type opType();
long estimateSize();
Source getSource();
long seqNo();
long primaryTerm();
/**
* Reads the type and the operation from the given stream. The operation must be written with
* {@link Operation#writeType(Operation, StreamOutput)}
*/
static Operation readType(StreamInput input) throws IOException {
Translog.Operation.Type type = Translog.Operation.Type.fromId(input.readByte());
switch (type) {
case CREATE:
// the deserialization logic in Index was identical to that of Create when create was deprecated
return new Index(input);
case DELETE:
return new Delete(input);
case INDEX:
return new Index(input);
case NO_OP:
return new NoOp(input);
default:
throw new IOException("No type for [" + type + "]");
}
}
/**
* Writes the type and translog operation to the given stream
*/
static void writeType(Translog.Operation operation, StreamOutput output) throws IOException {
output.writeByte(operation.opType().id());
operation.writeTo(output);
}
}
public static class Source {
public final BytesReference source;
public final String routing;
public final String parent;
public Source(BytesReference source, String routing, String parent) {
this.source = source;
this.routing = routing;
this.parent = parent;
}
}
public static class Index implements Operation {
public static final int FORMAT_2_X = 6; // since 2.0-beta1 and 1.1
public static final int FORMAT_AUTO_GENERATED_IDS = FORMAT_2_X + 1; // since 5.0.0-beta1
public static final int FORMAT_SEQ_NO = FORMAT_AUTO_GENERATED_IDS + 1; // since 6.0.0
public static final int SERIALIZATION_FORMAT = FORMAT_SEQ_NO;
private final String id;
private final long autoGeneratedIdTimestamp;
private final String type;
private long seqNo = SequenceNumbersService.UNASSIGNED_SEQ_NO;
private long primaryTerm = 0;
private final long version;
private final VersionType versionType;
private final BytesReference source;
private final String routing;
private final String parent;
public Index(StreamInput in) throws IOException {
final int format = in.readVInt(); // SERIALIZATION_FORMAT
assert format >= FORMAT_2_X : "format was: " + format;
id = in.readString();
type = in.readString();
source = in.readBytesReference();
routing = in.readOptionalString();
parent = in.readOptionalString();
this.version = in.readLong();
if (format < FORMAT_SEQ_NO) {
in.readLong(); // timestamp
in.readLong(); // ttl
}
this.versionType = VersionType.fromValue(in.readByte());
assert versionType.validateVersionForWrites(this.version) : "invalid version for writes: " + this.version;
if (format >= FORMAT_AUTO_GENERATED_IDS) {
this.autoGeneratedIdTimestamp = in.readLong();
} else {
this.autoGeneratedIdTimestamp = IndexRequest.UNSET_AUTO_GENERATED_TIMESTAMP;
}
if (format >= FORMAT_SEQ_NO) {
seqNo = in.readLong();
primaryTerm = in.readLong();
}
}
public Index(Engine.Index index, Engine.IndexResult indexResult) {
this.id = index.id();
this.type = index.type();
this.source = index.source();
this.routing = index.routing();
this.parent = index.parent();
this.seqNo = indexResult.getSeqNo();
this.primaryTerm = index.primaryTerm();
this.version = indexResult.getVersion();
this.versionType = index.versionType();
this.autoGeneratedIdTimestamp = index.getAutoGeneratedIdTimestamp();
}
public Index(String type, String id, byte[] source) {
this.type = type;
this.id = id;
this.source = new BytesArray(source);
this.seqNo = 0;
version = Versions.MATCH_ANY;
versionType = VersionType.INTERNAL;
routing = null;
parent = null;
autoGeneratedIdTimestamp = -1;
}
@Override
public Type opType() {
return Type.INDEX;
}
@Override
public long estimateSize() {
return ((id.length() + type.length()) * 2) + source.length() + 12;
}
public String type() {
return this.type;
}
public String id() {
return this.id;
}
public String routing() {
return this.routing;
}
public String parent() {
return this.parent;
}
public BytesReference source() {
return this.source;
}
@Override
public long seqNo() {
return seqNo;
}
@Override
public long primaryTerm() {
return primaryTerm;
}
public long version() {
return this.version;
}
public VersionType versionType() {
return versionType;
}
@Override
public Source getSource() {
return new Source(source, routing, parent);
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeVInt(SERIALIZATION_FORMAT);
out.writeString(id);
out.writeString(type);
out.writeBytesReference(source);
out.writeOptionalString(routing);
out.writeOptionalString(parent);
out.writeLong(version);
out.writeByte(versionType.getValue());
out.writeLong(autoGeneratedIdTimestamp);
out.writeLong(seqNo);
out.writeLong(primaryTerm);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Index index = (Index) o;
if (version != index.version ||
seqNo != index.seqNo ||
primaryTerm != index.primaryTerm ||
id.equals(index.id) == false ||
type.equals(index.type) == false ||
versionType != index.versionType ||
autoGeneratedIdTimestamp != index.autoGeneratedIdTimestamp ||
source.equals(index.source) == false) {
return false;
}
if (routing != null ? !routing.equals(index.routing) : index.routing != null) {
return false;
}
return !(parent != null ? !parent.equals(index.parent) : index.parent != null);
}
@Override
public int hashCode() {
int result = id.hashCode();
result = 31 * result + type.hashCode();
result = 31 * result + Long.hashCode(seqNo);
result = 31 * result + Long.hashCode(primaryTerm);
result = 31 * result + Long.hashCode(version);
result = 31 * result + versionType.hashCode();
result = 31 * result + source.hashCode();
result = 31 * result + (routing != null ? routing.hashCode() : 0);
result = 31 * result + (parent != null ? parent.hashCode() : 0);
result = 31 * result + Long.hashCode(autoGeneratedIdTimestamp);
return result;
}
@Override
public String toString() {
return "Index{" +
"id='" + id + '\'' +
", type='" + type + '\'' +
'}';
}
public long getAutoGeneratedIdTimestamp() {
return autoGeneratedIdTimestamp;
}
}
public static class Delete implements Operation {
private static final int FORMAT_5_X = 2;
private static final int FORMAT_SEQ_NO = FORMAT_5_X + 1;
public static final int SERIALIZATION_FORMAT = FORMAT_SEQ_NO;
private String type, id;
private Term uid;
private long seqNo = SequenceNumbersService.UNASSIGNED_SEQ_NO;
private long primaryTerm = 0;
private long version = Versions.MATCH_ANY;
private VersionType versionType = VersionType.INTERNAL;
public Delete(StreamInput in) throws IOException {
final int format = in.readVInt();// SERIALIZATION_FORMAT
assert format >= FORMAT_5_X : "format was: " + format;
uid = new Term(in.readString(), in.readString());
this.version = in.readLong();
this.versionType = VersionType.fromValue(in.readByte());
assert versionType.validateVersionForWrites(this.version);
if (format >= FORMAT_SEQ_NO) {
seqNo = in.readLong();
primaryTerm = in.readLong();
}
}
public Delete(Engine.Delete delete, Engine.DeleteResult deleteResult) {
this(delete.type(), delete.id(), delete.uid(), deleteResult.getSeqNo(), delete.primaryTerm(), deleteResult.getVersion(), delete.versionType());
}
/** utility for testing */
public Delete(String type, String id, Term uid) {
this(type, id, uid, 0, 0, Versions.MATCH_ANY, VersionType.INTERNAL);
}
public Delete(String type, String id, Term uid, long seqNo, long primaryTerm, long version, VersionType versionType) {
this.type = type;
this.id = id;
this.uid = uid;
this.seqNo = seqNo;
this.primaryTerm = primaryTerm;
this.version = version;
this.versionType = versionType;
}
@Override
public Type opType() {
return Type.DELETE;
}
@Override
public long estimateSize() {
return ((uid.field().length() + uid.text().length()) * 2) + 20;
}
public String type() {
return type;
}
public String id() {
return id;
}
public Term uid() {
return this.uid;
}
@Override
public long seqNo() {
return seqNo;
}
@Override
public long primaryTerm() {
return primaryTerm;
}
public long version() {
return this.version;
}
public VersionType versionType() {
return this.versionType;
}
@Override
public Source getSource() {
throw new IllegalStateException("trying to read doc source from delete operation");
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeVInt(SERIALIZATION_FORMAT);
out.writeString(uid.field());
out.writeString(uid.text());
out.writeLong(version);
out.writeByte(versionType.getValue());
out.writeLong(seqNo);
out.writeLong(primaryTerm);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Delete delete = (Delete) o;
return version == delete.version &&
seqNo == delete.seqNo &&
primaryTerm == delete.primaryTerm &&
uid.equals(delete.uid) &&
versionType == delete.versionType;
}
@Override
public int hashCode() {
int result = uid.hashCode();
result = 31 * result + Long.hashCode(seqNo);
result = 31 * result + Long.hashCode(primaryTerm);
result = 31 * result + Long.hashCode(version);
result = 31 * result + versionType.hashCode();
return result;
}
@Override
public String toString() {
return "Delete{" +
"uid=" + uid +
'}';
}
}
public static class NoOp implements Operation {
private final long seqNo;
private final long primaryTerm;
private final String reason;
@Override
public long seqNo() {
return seqNo;
}
@Override
public long primaryTerm() {
return primaryTerm;
}
public String reason() {
return reason;
}
NoOp(final StreamInput in) throws IOException {
seqNo = in.readLong();
primaryTerm = in.readLong();
reason = in.readString();
}
public NoOp(final long seqNo, final long primaryTerm, final String reason) {
assert seqNo > SequenceNumbersService.NO_OPS_PERFORMED;
assert primaryTerm >= 0;
assert reason != null;
this.seqNo = seqNo;
this.primaryTerm = primaryTerm;
this.reason = reason;
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeLong(seqNo);
out.writeLong(primaryTerm);
out.writeString(reason);
}
@Override
public Type opType() {
return Type.NO_OP;
}
@Override
public long estimateSize() {
return 2 * reason.length() + 2 * Long.BYTES;
}
@Override
public Source getSource() {
throw new UnsupportedOperationException("source does not exist for a no-op");
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || getClass() != obj.getClass()) {
return false;
}
final NoOp that = (NoOp) obj;
return seqNo == that.seqNo && primaryTerm == that.primaryTerm && reason.equals(that.reason);
}
@Override
public int hashCode() {
return 31 * 31 * 31 + 31 * 31 * Long.hashCode(seqNo) + 31 * Long.hashCode(primaryTerm) + reason().hashCode();
}
}
public enum Durability {
/**
* Async durability - translogs are synced based on a time interval.
*/
ASYNC,
/**
* Request durability - translogs are synced for each high level request (bulk, index, delete)
*/
REQUEST
}
private static void verifyChecksum(BufferedChecksumStreamInput in) throws IOException {
// This absolutely must come first, or else reading the checksum becomes part of the checksum
long expectedChecksum = in.getChecksum();
long readChecksum = in.readInt() & 0xFFFF_FFFFL;
if (readChecksum != expectedChecksum) {
throw new TranslogCorruptedException("translog stream is corrupted, expected: 0x" +
Long.toHexString(expectedChecksum) + ", got: 0x" + Long.toHexString(readChecksum));
}
}
/**
* Reads a list of operations written with {@link #writeOperations(StreamOutput, List)}
*/
public static List<Operation> readOperations(StreamInput input) throws IOException {
ArrayList<Operation> operations = new ArrayList<>();
int numOps = input.readInt();
final BufferedChecksumStreamInput checksumStreamInput = new BufferedChecksumStreamInput(input);
for (int i = 0; i < numOps; i++) {
operations.add(readOperation(checksumStreamInput));
}
return operations;
}
static Translog.Operation readOperation(BufferedChecksumStreamInput in) throws IOException {
final Translog.Operation operation;
try {
final int opSize = in.readInt();
if (opSize < 4) { // 4byte for the checksum
throw new TranslogCorruptedException("operation size must be at least 4 but was: " + opSize);
}
in.resetDigest(); // size is not part of the checksum!
if (in.markSupported()) { // if we can we validate the checksum first
// we are sometimes called when mark is not supported this is the case when
// we are sending translogs across the network with LZ4 compression enabled - currently there is no way s
// to prevent this unfortunately.
in.mark(opSize);
in.skip(opSize - 4);
verifyChecksum(in);
in.reset();
}
operation = Translog.Operation.readType(in);
verifyChecksum(in);
} catch (TranslogCorruptedException e) {
throw e;
} catch (EOFException e) {
throw new TruncatedTranslogException("reached premature end of file, translog is truncated", e);
}
return operation;
}
/**
* Writes all operations in the given iterable to the given output stream including the size of the array
* use {@link #readOperations(StreamInput)} to read it back.
*/
public static void writeOperations(StreamOutput outStream, List<Operation> toWrite) throws IOException {
final ReleasableBytesStreamOutput out = new ReleasableBytesStreamOutput(BigArrays.NON_RECYCLING_INSTANCE);
try {
outStream.writeInt(toWrite.size());
final BufferedChecksumStreamOutput checksumStreamOutput = new BufferedChecksumStreamOutput(out);
for (Operation op : toWrite) {
out.reset();
final long start = out.position();
out.skip(Integer.BYTES);
writeOperationNoSize(checksumStreamOutput, op);
long end = out.position();
int operationSize = (int) (out.position() - Integer.BYTES - start);
out.seek(start);
out.writeInt(operationSize);
out.seek(end);
ReleasablePagedBytesReference bytes = out.bytes();
bytes.writeTo(outStream);
}
} finally {
Releasables.close(out);
}
}
public static void writeOperationNoSize(BufferedChecksumStreamOutput out, Translog.Operation op) throws IOException {
// This BufferedChecksumStreamOutput remains unclosed on purpose,
// because closing it closes the underlying stream, which we don't
// want to do here.
out.resetDigest();
Translog.Operation.writeType(op, out);
long checksum = out.getChecksum();
out.writeInt((int) checksum);
}
/**
* Gets the minimum generation that could contain any sequence number after the specified sequence number, or the current generation if
* there is no generation that could any such sequence number.
*
* @param seqNo the sequence number
* @return the minimum generation for the sequence number
*/
public TranslogGeneration getMinGenerationForSeqNo(final long seqNo) {
try (ReleasableLock ignored = writeLock.acquire()) {
/*
* When flushing, the engine will ask the translog for the minimum generation that could contain any sequence number after the
* local checkpoint. Immediately after flushing, there will be no such generation, so this minimum generation in this case will
* be the current translog generation as we do not need any prior generations to have a complete history up to the current local
* checkpoint.
*/
long minTranslogFileGeneration = this.currentFileGeneration();
for (final TranslogReader reader : readers) {
if (seqNo <= reader.getCheckpoint().maxSeqNo) {
minTranslogFileGeneration = Math.min(minTranslogFileGeneration, reader.getGeneration());
}
}
return new TranslogGeneration(translogUUID, minTranslogFileGeneration);
}
}
/**
* Roll the current translog generation into a new generation. This does not commit the
* translog.
*
* @throws IOException if an I/O exception occurred during any file operations
*/
public void rollGeneration() throws IOException {
try (Releasable ignored = writeLock.acquire()) {
try {
final TranslogReader reader = current.closeIntoReader();
readers.add(reader);
final Path checkpoint = location.resolve(CHECKPOINT_FILE_NAME);
assert Checkpoint.read(checkpoint).generation == current.getGeneration();
final Path generationCheckpoint =
location.resolve(getCommitCheckpointFileName(current.getGeneration()));
Files.copy(checkpoint, generationCheckpoint);
IOUtils.fsync(generationCheckpoint, false);
IOUtils.fsync(generationCheckpoint.getParent(), true);
// create a new translog file; this will sync it and update the checkpoint data;
current = createWriter(current.getGeneration() + 1);
logger.trace("current translog set to [{}]", current.getGeneration());
} catch (final Exception e) {
IOUtils.closeWhileHandlingException(this); // tragic event
throw e;
}
}
}
/**
* Prepares a translog commit by setting the current committing generation and rolling the translog generation.
*
* @throws IOException if an I/O exception occurred while rolling the translog generation
*/
public void prepareCommit() throws IOException {
try (ReleasableLock ignored = writeLock.acquire()) {
ensureOpen();
if (currentCommittingGeneration != NOT_SET_GENERATION) {
final String message =
String.format(Locale.ROOT, "already committing a translog with generation [%d]", currentCommittingGeneration);
throw new IllegalStateException(message);
}
currentCommittingGeneration = current.getGeneration();
rollGeneration();
}
}
/**
* Commits the translog and sets the last committed translog generation to the specified generation. The specified committed generation
* will be used when trimming unreferenced translog generations such that generations from the committed generation will be preserved.
*
* If {@link Translog#prepareCommit()} was not called before calling commit, this method will be invoked too causing the translog
* generation to be rolled.
*
* @param committedGeneration the minimum translog generation to preserve after trimming unreferenced generations
* @throws IOException if an I/O exception occurred preparing the translog commit
*/
public void commit(final long committedGeneration) throws IOException {
try (ReleasableLock ignored = writeLock.acquire()) {
ensureOpen();
assert assertCommittedGenerationIsInValidRange(committedGeneration);
if (currentCommittingGeneration == NOT_SET_GENERATION) {
prepareCommit();
}
assert currentCommittingGeneration != NOT_SET_GENERATION;
assert readers.stream().anyMatch(r -> r.getGeneration() == currentCommittingGeneration)
: "readers missing committing generation [" + currentCommittingGeneration + "]";
// set the last committed generation otherwise old files will not be cleaned up
lastCommittedTranslogFileGeneration = committedGeneration;
currentCommittingGeneration = NOT_SET_GENERATION;
trimUnreferencedReaders();
}
}
private boolean assertCommittedGenerationIsInValidRange(final long committedGeneration) {
assert committedGeneration <= current.generation
: "tried to commit generation [" + committedGeneration + "] after current generation [" + current.generation + "]";
final long min = readers.stream().map(TranslogReader::getGeneration).min(Long::compareTo).orElse(Long.MIN_VALUE);
assert committedGeneration >= min
: "tried to commit generation [" + committedGeneration + "] before minimum generation [" + min + "]";
return true;
}
/**
* Trims unreferenced translog generations. The guarantee here is that translog generations will be preserved for all outstanding views
* and from the last committed translog generation defined by {@link Translog#lastCommittedTranslogFileGeneration}.
*/
void trimUnreferencedReaders() {
try (ReleasableLock ignored = writeLock.acquire()) {
if (closed.get()) {
// we're shutdown potentially on some tragic event, don't delete anything
return;
}
long minReferencedGen = Math.min(
lastCommittedTranslogFileGeneration,
outstandingViews.stream().mapToLong(View::minTranslogGeneration).min().orElse(Long.MAX_VALUE));
final List<TranslogReader> unreferenced =
readers.stream().filter(r -> r.getGeneration() < minReferencedGen).collect(Collectors.toList());
for (final TranslogReader unreferencedReader : unreferenced) {
final Path translogPath = unreferencedReader.path();
logger.trace("delete translog file [{}], not referenced and not current anymore", translogPath);
IOUtils.closeWhileHandlingException(unreferencedReader);
IOUtils.deleteFilesIgnoringExceptions(translogPath,
translogPath.resolveSibling(getCommitCheckpointFileName(unreferencedReader.getGeneration())));
}
readers.removeAll(unreferenced);
}
}
void closeFilesIfNoPendingViews() throws IOException {
try (ReleasableLock ignored = writeLock.acquire()) {
if (closed.get() && outstandingViews.isEmpty()) {
logger.trace("closing files. translog is closed and there are no pending views");
ArrayList<Closeable> toClose = new ArrayList<>(readers);
toClose.add(current);
IOUtils.close(toClose);
}
}
}
/**
* References a transaction log generation
*/
public static final class TranslogGeneration {
public final String translogUUID;
public final long translogFileGeneration;
public TranslogGeneration(String translogUUID, long translogFileGeneration) {
this.translogUUID = translogUUID;
this.translogFileGeneration = translogFileGeneration;
}
}
/**
* Returns the current generation of this translog. This corresponds to the latest uncommitted translog generation
*/
public TranslogGeneration getGeneration() {
try (ReleasableLock lock = writeLock.acquire()) {
return new TranslogGeneration(translogUUID, currentFileGeneration());
}
}
/**
* Returns <code>true</code> iff the given generation is the current generation of this translog
*/
public boolean isCurrent(TranslogGeneration generation) {
try (ReleasableLock lock = writeLock.acquire()) {
if (generation != null) {
if (generation.translogUUID.equals(translogUUID) == false) {
throw new IllegalArgumentException("commit belongs to a different translog: " + generation.translogUUID + " vs. " + translogUUID);
}
return generation.translogFileGeneration == currentFileGeneration();
}
}
return false;
}
long getFirstOperationPosition() { // for testing
return current.getFirstOperationOffset();
}
private void ensureOpen() {
if (closed.get()) {
throw new AlreadyClosedException("translog is already closed", current.getTragicException());
}
}
/**
* The number of currently open views
*/
int getNumOpenViews() {
return outstandingViews.size();
}
ChannelFactory getChannelFactory() {
return FileChannel::open;
}
/**
* If this {@code Translog} was closed as a side-effect of a tragic exception,
* e.g. disk full while flushing a new segment, this returns the root cause exception.
* Otherwise (no tragic exception has occurred) it returns null.
*/
public Exception getTragicException() {
return current.getTragicException();
}
/** Reads and returns the current checkpoint */
static final Checkpoint readCheckpoint(final Path location) throws IOException {
return Checkpoint.read(location.resolve(CHECKPOINT_FILE_NAME));
}
/**
* Reads the sequence numbers global checkpoint from the translog checkpoint.
*
* @param location the location of the translog
* @return the global checkpoint
* @throws IOException if an I/O exception occurred reading the checkpoint
*/
public static final long readGlobalCheckpoint(final Path location) throws IOException {
return readCheckpoint(location).globalCheckpoint;
}
/**
* Returns the translog uuid used to associate a lucene index with a translog.
*/
public String getTranslogUUID() {
return translogUUID;
}
}