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[RCI] Add NoOpEngine for closed indices (#33903)
This commit adds a new NoOpEngine implementation based on the current ReadOnlyEngine. This new implementation uses an empty DirectoryReader with no segments readers and will always returns 0 docs. The NoOpEngine is the default Engine created for IndexShards of closed indices. It expects an empty translog when it is instantiated. Relates to #33888
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server/src/main/java/org/elasticsearch/index/engine/NoOpEngine.java
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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. | ||
| */ | ||
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| package org.elasticsearch.index.engine; | ||
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| import org.apache.lucene.index.DirectoryReader; | ||
| import org.apache.lucene.index.IndexCommit; | ||
| import org.apache.lucene.index.IndexWriter; | ||
| import org.apache.lucene.index.LeafReader; | ||
| import org.apache.lucene.store.Directory; | ||
| import org.elasticsearch.common.Nullable; | ||
| import org.elasticsearch.core.internal.io.IOUtils; | ||
| import org.elasticsearch.index.translog.Translog; | ||
| import org.elasticsearch.index.translog.TranslogConfig; | ||
| import org.elasticsearch.index.translog.TranslogCorruptedException; | ||
| import org.elasticsearch.index.translog.TranslogDeletionPolicy; | ||
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| import java.io.IOException; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.function.LongSupplier; | ||
| import java.util.stream.Stream; | ||
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| /** | ||
| * NoOpEngine is an engine implementation that does nothing but the bare minimum | ||
| * required in order to have an engine. All attempts to do something (search, | ||
| * index, get), throw {@link UnsupportedOperationException}. This does maintain | ||
| * a translog with a deletion policy so that when flushing, no translog is | ||
| * retained on disk (setting a retention size and age of 0). | ||
| * | ||
| * It's also important to notice that this does list the commits of the Store's | ||
| * Directory so that the last commit's user data can be read for the historyUUID | ||
| * and last committed segment info. | ||
| */ | ||
| public final class NoOpEngine extends ReadOnlyEngine { | ||
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| public NoOpEngine(EngineConfig engineConfig) { | ||
| super(engineConfig, null, null, true, directoryReader -> directoryReader); | ||
| boolean success = false; | ||
| try { | ||
| // The deletion policy for the translog should not keep any translogs around, so the min age/size is set to -1 | ||
| final TranslogDeletionPolicy translogDeletionPolicy = new TranslogDeletionPolicy(-1, -1); | ||
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| // The translog is opened and closed to validate that the translog UUID from lucene is the same as the one in the translog | ||
| try (Translog translog = openTranslog(engineConfig, translogDeletionPolicy, engineConfig.getGlobalCheckpointSupplier())) { | ||
| final int nbOperations = translog.totalOperations(); | ||
| if (nbOperations != 0) { | ||
| throw new IllegalArgumentException("Expected 0 translog operations but there were " + nbOperations); | ||
| } | ||
| } | ||
| success = true; | ||
| } catch (IOException | TranslogCorruptedException e) { | ||
| throw new EngineCreationFailureException(shardId, "failed to create engine", e); | ||
| } finally { | ||
| if (success == false) { | ||
| IOUtils.closeWhileHandlingException(this); | ||
| } | ||
| } | ||
| } | ||
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| @Override | ||
| protected DirectoryReader open(final Directory directory) throws IOException { | ||
| final List<IndexCommit> indexCommits = DirectoryReader.listCommits(directory); | ||
| assert indexCommits.size() == 1 : "expected only one commit point"; | ||
| IndexCommit indexCommit = indexCommits.get(indexCommits.size() - 1); | ||
| return new DirectoryReader(directory, new LeafReader[0]) { | ||
| @Override | ||
| protected DirectoryReader doOpenIfChanged() throws IOException { | ||
| return null; | ||
| } | ||
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| @Override | ||
| protected DirectoryReader doOpenIfChanged(IndexCommit commit) throws IOException { | ||
| return null; | ||
| } | ||
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| @Override | ||
| protected DirectoryReader doOpenIfChanged(IndexWriter writer, boolean applyAllDeletes) throws IOException { | ||
| return null; | ||
| } | ||
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| @Override | ||
| public long getVersion() { | ||
| return 0; | ||
| } | ||
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| @Override | ||
| public boolean isCurrent() throws IOException { | ||
| return true; | ||
| } | ||
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| @Override | ||
| public IndexCommit getIndexCommit() throws IOException { | ||
| return indexCommit; | ||
| } | ||
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| @Override | ||
| protected void doClose() throws IOException { | ||
| } | ||
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| @Override | ||
| public CacheHelper getReaderCacheHelper() { | ||
| return null; | ||
| } | ||
| }; | ||
| } | ||
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| private Translog openTranslog(EngineConfig engineConfig, TranslogDeletionPolicy translogDeletionPolicy, | ||
| LongSupplier globalCheckpointSupplier) throws IOException { | ||
| final TranslogConfig translogConfig = engineConfig.getTranslogConfig(); | ||
| final String translogUUID = loadTranslogUUIDFromLastCommit(); | ||
| // We expect that this shard already exists, so it must already have an existing translog else something is badly wrong! | ||
| return new Translog(translogConfig, translogUUID, translogDeletionPolicy, globalCheckpointSupplier, | ||
| engineConfig.getPrimaryTermSupplier()); | ||
| } | ||
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| /** | ||
| * Reads the current stored translog ID from the last commit data. | ||
| */ | ||
| @Nullable | ||
| private String loadTranslogUUIDFromLastCommit() { | ||
| final Map<String, String> commitUserData = getLastCommittedSegmentInfos().getUserData(); | ||
| if (commitUserData.containsKey(Translog.TRANSLOG_GENERATION_KEY) == false) { | ||
| throw new IllegalStateException("Commit doesn't contain translog generation id"); | ||
| } | ||
| return commitUserData.get(Translog.TRANSLOG_UUID_KEY); | ||
| } | ||
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| @Override | ||
| public boolean ensureTranslogSynced(Stream<Translog.Location> locations) { | ||
| throw new UnsupportedOperationException("Translog synchronization should never be needed"); | ||
| } | ||
| } |
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