org.elasticsearch.index.engine.CombinedDeletionPolicy Maven / Gradle / Ivy
Show all versions of elasticsearch Show documentation
/*
* 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.engine;
import com.carrotsearch.hppc.ObjectIntHashMap;
import org.apache.logging.log4j.Logger;
import org.apache.lucene.index.IndexCommit;
import org.apache.lucene.index.IndexDeletionPolicy;
import org.apache.lucene.store.Directory;
import org.elasticsearch.index.seqno.SequenceNumbers;
import org.elasticsearch.index.translog.Translog;
import org.elasticsearch.index.translog.TranslogDeletionPolicy;
import java.io.IOException;
import java.nio.file.Path;
import java.util.Collection;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.function.LongSupplier;
/**
* An {@link IndexDeletionPolicy} that coordinates between Lucene's commits and the retention of translog generation files,
* making sure that all translog files that are needed to recover from the Lucene commit are not deleted.
*
* In particular, this policy will delete index commits whose max sequence number is at most
* the current global checkpoint except the index commit which has the highest max sequence number among those.
*/
public final class CombinedDeletionPolicy extends IndexDeletionPolicy {
private final Logger logger;
private final TranslogDeletionPolicy translogDeletionPolicy;
private final SoftDeletesPolicy softDeletesPolicy;
private final LongSupplier globalCheckpointSupplier;
private final ObjectIntHashMap snapshottedCommits; // Number of snapshots held against each commit point.
private volatile IndexCommit safeCommit; // the most recent safe commit point - its max_seqno at most the persisted global checkpoint.
private volatile IndexCommit lastCommit; // the most recent commit point
CombinedDeletionPolicy(Logger logger, TranslogDeletionPolicy translogDeletionPolicy,
SoftDeletesPolicy softDeletesPolicy, LongSupplier globalCheckpointSupplier) {
this.logger = logger;
this.translogDeletionPolicy = translogDeletionPolicy;
this.softDeletesPolicy = softDeletesPolicy;
this.globalCheckpointSupplier = globalCheckpointSupplier;
this.snapshottedCommits = new ObjectIntHashMap<>();
}
@Override
public synchronized void onInit(List commits) throws IOException {
assert commits.isEmpty() == false : "index is opened, but we have no commits";
onCommit(commits);
if (safeCommit != commits.get(commits.size() - 1)) {
throw new IllegalStateException("Engine is opened, but the last commit isn't safe. Global checkpoint ["
+ globalCheckpointSupplier.getAsLong() + "], seqNo is last commit ["
+ SequenceNumbers.loadSeqNoInfoFromLuceneCommit(lastCommit.getUserData().entrySet()) + "], "
+ "seqNos in safe commit [" + SequenceNumbers.loadSeqNoInfoFromLuceneCommit(safeCommit.getUserData().entrySet()) + "]");
}
}
@Override
public synchronized void onCommit(List commits) throws IOException {
final int keptPosition = indexOfKeptCommits(commits, globalCheckpointSupplier.getAsLong());
lastCommit = commits.get(commits.size() - 1);
safeCommit = commits.get(keptPosition);
for (int i = 0; i < keptPosition; i++) {
if (snapshottedCommits.containsKey(commits.get(i)) == false) {
deleteCommit(commits.get(i));
}
}
updateRetentionPolicy();
}
private void deleteCommit(IndexCommit commit) throws IOException {
assert commit.isDeleted() == false : "Index commit [" + commitDescription(commit) + "] is deleted twice";
logger.debug("Delete index commit [{}]", commitDescription(commit));
commit.delete();
assert commit.isDeleted() : "Deletion commit [" + commitDescription(commit) + "] was suppressed";
}
private void updateRetentionPolicy() throws IOException {
assert Thread.holdsLock(this);
logger.debug("Safe commit [{}], last commit [{}]", commitDescription(safeCommit), commitDescription(lastCommit));
assert safeCommit.isDeleted() == false : "The safe commit must not be deleted";
final long minRequiredGen = Long.parseLong(safeCommit.getUserData().get(Translog.TRANSLOG_GENERATION_KEY));
assert lastCommit.isDeleted() == false : "The last commit must not be deleted";
final long lastGen = Long.parseLong(lastCommit.getUserData().get(Translog.TRANSLOG_GENERATION_KEY));
assert minRequiredGen <= lastGen : "minRequiredGen must not be greater than lastGen";
translogDeletionPolicy.setTranslogGenerationOfLastCommit(lastGen);
translogDeletionPolicy.setMinTranslogGenerationForRecovery(minRequiredGen);
softDeletesPolicy.setLocalCheckpointOfSafeCommit(
Long.parseLong(safeCommit.getUserData().get(SequenceNumbers.LOCAL_CHECKPOINT_KEY)));
}
/**
* Captures the most recent commit point {@link #lastCommit} or the most recent safe commit point {@link #safeCommit}.
* Index files of the capturing commit point won't be released until the commit reference is closed.
*
* @param acquiringSafeCommit captures the most recent safe commit point if true; otherwise captures the most recent commit point.
*/
synchronized IndexCommit acquireIndexCommit(boolean acquiringSafeCommit) {
assert safeCommit != null : "Safe commit is not initialized yet";
assert lastCommit != null : "Last commit is not initialized yet";
final IndexCommit snapshotting = acquiringSafeCommit ? safeCommit : lastCommit;
snapshottedCommits.addTo(snapshotting, 1); // increase refCount
return new SnapshotIndexCommit(snapshotting);
}
/**
* Releases an index commit that acquired by {@link #acquireIndexCommit(boolean)}.
*
* @return true if the snapshotting commit can be clean up.
*/
synchronized boolean releaseCommit(final IndexCommit snapshotCommit) {
final IndexCommit releasingCommit = ((SnapshotIndexCommit) snapshotCommit).delegate;
assert snapshottedCommits.containsKey(releasingCommit) : "Release non-snapshotted commit;" +
"snapshotted commits [" + snapshottedCommits + "], releasing commit [" + releasingCommit + "]";
final int refCount = snapshottedCommits.addTo(releasingCommit, -1); // release refCount
assert refCount >= 0 : "Number of snapshots can not be negative [" + refCount + "]";
if (refCount == 0) {
snapshottedCommits.remove(releasingCommit);
}
// The commit can be clean up only if no pending snapshot and it is neither the safe commit nor last commit.
return refCount == 0 && releasingCommit.equals(safeCommit) == false && releasingCommit.equals(lastCommit) == false;
}
/**
* Find a safe commit point from a list of existing commits based on the supplied global checkpoint.
* The max sequence number of a safe commit point should be at most the global checkpoint.
* If an index was created before v6.2, and we haven't retained a safe commit yet, this method will return the oldest commit.
*
* @param commits a list of existing commit points
* @param globalCheckpoint the persisted global checkpoint from the translog, see {@link Translog#readGlobalCheckpoint(Path, String)}
* @return a safe commit or the oldest commit if a safe commit is not found
*/
public static IndexCommit findSafeCommitPoint(List commits, long globalCheckpoint) throws IOException {
if (commits.isEmpty()) {
throw new IllegalArgumentException("Commit list must not empty");
}
final int keptPosition = indexOfKeptCommits(commits, globalCheckpoint);
return commits.get(keptPosition);
}
/**
* Find the highest index position of a safe index commit whose max sequence number is not greater than the global checkpoint.
* Index commits with different translog UUID will be filtered out as they don't belong to this engine.
*/
private static int indexOfKeptCommits(List commits, long globalCheckpoint) throws IOException {
final String expectedTranslogUUID = commits.get(commits.size() - 1).getUserData().get(Translog.TRANSLOG_UUID_KEY);
// Commits are sorted by age (the 0th one is the oldest commit).
for (int i = commits.size() - 1; i >= 0; i--) {
final Map commitUserData = commits.get(i).getUserData();
// Ignore index commits with different translog uuid.
if (expectedTranslogUUID.equals(commitUserData.get(Translog.TRANSLOG_UUID_KEY)) == false) {
return i + 1;
}
// 5.x commits do not contain MAX_SEQ_NO, we should not keep it and the older commits.
if (commitUserData.containsKey(SequenceNumbers.MAX_SEQ_NO) == false) {
return Math.min(commits.size() - 1, i + 1);
}
final long maxSeqNoFromCommit = Long.parseLong(commitUserData.get(SequenceNumbers.MAX_SEQ_NO));
// If a 6.x node with a 5.x index is promoted to be a primary, it will flush a new index commit to
// make sure translog operations without seqno will never be replayed (see IndexShard#updateShardState).
// However the global checkpoint is still UNASSIGNED and the max_seqno of both commits are NO_OPS_PERFORMED.
// If this policy considers the first commit as a safe commit, we will send the first commit without replaying
// translog between these commits to the replica in a peer-recovery. This causes the replica missing those operations.
// To prevent this, we should not keep more than one commit whose max_seqno is NO_OPS_PERFORMED.
// Once we can retain a safe commit, a NO_OPS_PERFORMED commit will be deleted just as other commits.
if (maxSeqNoFromCommit == SequenceNumbers.NO_OPS_PERFORMED) {
return i;
}
if (maxSeqNoFromCommit <= globalCheckpoint) {
return i;
}
}
/*
* We may reach to this point in these cases:
* 1. In the previous 6.x, we keep only the last commit - which is likely not a safe commit if writes are in progress.
* Thus, after upgrading, we may not find a safe commit until we can reserve one.
* 2. In peer-recovery, if the file-based happens, a replica will be received the latest commit from a primary.
* However, that commit may not be a safe commit if writes are in progress in the primary.
*/
return 0;
}
/**
* Checks whether the deletion policy is holding on to snapshotted commits
*/
synchronized boolean hasSnapshottedCommits() {
return snapshottedCommits.isEmpty() == false;
}
/**
* Checks if the deletion policy can release some index commits with the latest global checkpoint.
*/
boolean hasUnreferencedCommits() throws IOException {
final IndexCommit lastCommit = this.lastCommit;
if (safeCommit != lastCommit) { // Race condition can happen but harmless
if (lastCommit.getUserData().containsKey(SequenceNumbers.MAX_SEQ_NO)) {
final long maxSeqNoFromLastCommit = Long.parseLong(lastCommit.getUserData().get(SequenceNumbers.MAX_SEQ_NO));
// We can clean up the current safe commit if the last commit is safe
return globalCheckpointSupplier.getAsLong() >= maxSeqNoFromLastCommit;
}
}
return false;
}
/**
* Returns a description for a given {@link IndexCommit}. This should be only used for logging and debugging.
*/
public static String commitDescription(IndexCommit commit) throws IOException {
return String.format(Locale.ROOT, "CommitPoint{segment[%s], userData[%s]}", commit.getSegmentsFileName(), commit.getUserData());
}
/**
* A wrapper of an index commit that prevents it from being deleted.
*/
private static class SnapshotIndexCommit extends IndexCommit {
private final IndexCommit delegate;
SnapshotIndexCommit(IndexCommit delegate) {
this.delegate = delegate;
}
@Override
public String getSegmentsFileName() {
return delegate.getSegmentsFileName();
}
@Override
public Collection getFileNames() throws IOException {
return delegate.getFileNames();
}
@Override
public Directory getDirectory() {
return delegate.getDirectory();
}
@Override
public void delete() {
throw new UnsupportedOperationException("A snapshot commit does not support deletion");
}
@Override
public boolean isDeleted() {
return delegate.isDeleted();
}
@Override
public int getSegmentCount() {
return delegate.getSegmentCount();
}
@Override
public long getGeneration() {
return delegate.getGeneration();
}
@Override
public Map getUserData() throws IOException {
return delegate.getUserData();
}
@Override
public String toString() {
return "SnapshotIndexCommit{" + delegate + "}";
}
}
}