Add ElasticsearchIndexDeletionPolicy and EngineConfig policy wrapper

server/src/internalClusterTest/java/org/elasticsearch/indices/IndexingMemoryControllerIT.java

@@ -89,7 +89,8 @@ EngineConfig engineConfigWithLargerIndexingMemory(EngineConfig config) {
                 config.isPromotableToPrimary(),
                 config.getMapperService(),
                 config.getEngineResetLock(),
-                config.getMergeMetrics()
+                config.getMergeMetrics(),
+                config.getIndexDeletionPolicyWrapper()
             );
         }
 

server/src/main/java/org/elasticsearch/common/lucene/FilterIndexCommit.java

@@ -71,4 +71,11 @@ public Map<String, String> getUserData() throws IOException {
     public String toString() {
         return "FilterIndexCommit{" + "in=" + in + '}';
     }
+
+    public static IndexCommit unwrap(IndexCommit in) {
+        while (in instanceof FilterIndexCommit) {
+            in = ((FilterIndexCommit) in).getIndexCommit();
+        }
+        return in;
+    }
 }

server/src/main/java/org/elasticsearch/index/engine/CombinedDeletionPolicy.java

@@ -38,7 +38,7 @@
  * 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 class CombinedDeletionPolicy extends IndexDeletionPolicy {
+public class CombinedDeletionPolicy extends ElasticsearchIndexDeletionPolicy {
     private final Logger logger;
     private final TranslogDeletionPolicy translogDeletionPolicy;
     private final SoftDeletesPolicy softDeletesPolicy;
@@ -48,13 +48,6 @@ public class CombinedDeletionPolicy extends IndexDeletionPolicy {
     // when checking for externally acquired index commits that haven't been released
     private final Set<IndexCommit> internallyAcquiredIndexCommits;
 
-    interface CommitsListener {
-
-        void onNewAcquiredCommit(IndexCommit commit, Set<String> additionalFiles);
-
-        void onDeletedCommit(IndexCommit commit);
-    }
-
     @Nullable
     private final CommitsListener commitsListener;
 
@@ -187,7 +180,6 @@ 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 {
@@ -204,7 +196,8 @@ protected int getDocCountOfCommit(IndexCommit indexCommit) throws IOException {
         return SegmentInfos.readCommit(indexCommit.getDirectory(), indexCommit.getSegmentsFileName()).totalMaxDoc();
     }
 
-    SafeCommitInfo getSafeCommitInfo() {
+    @Override
+    public SafeCommitInfo getSafeCommitInfo() {
         return safeCommitInfo;
     }
 
@@ -214,7 +207,8 @@ SafeCommitInfo getSafeCommitInfo() {
      *
      * @param acquiringSafeCommit captures the most recent safe commit point if true; otherwise captures the most recent commit point.
      */
-    synchronized IndexCommit acquireIndexCommit(boolean acquiringSafeCommit) {
+    @Override
+    public synchronized IndexCommit acquireIndexCommit(boolean acquiringSafeCommit) {
         return acquireIndexCommit(acquiringSafeCommit, false);
     }
 
@@ -241,7 +235,8 @@ protected IndexCommit wrapCommit(IndexCommit indexCommit, boolean acquiredIntern
      *
      * @return true if the acquired commit can be clean up.
      */
-    synchronized boolean releaseCommit(final IndexCommit acquiredCommit) {
+    @Override
+    public synchronized boolean releaseIndexCommit(final IndexCommit acquiredCommit) {
         final SnapshotIndexCommit snapshotIndexCommit = (SnapshotIndexCommit) acquiredCommit;
         final IndexCommit releasingCommit = snapshotIndexCommit.getIndexCommit();
         assert acquiredIndexCommits.containsKey(releasingCommit)
@@ -316,7 +311,8 @@ private static Set<String> listOfNewFileNames(IndexCommit previous, IndexCommit
     /**
      * Checks whether the deletion policy is holding on to externally acquired index commits
      */
-    synchronized boolean hasAcquiredIndexCommitsForTesting() {
+    @Override
+    public synchronized boolean hasAcquiredIndexCommitsForTesting() {
         // We explicitly check only external commits and disregard internal commits acquired by the commits listener
         for (var e : acquiredIndexCommits.entrySet()) {
             if (internallyAcquiredIndexCommits.contains(e.getKey()) == false || e.getValue() > 1) {
@@ -329,7 +325,8 @@ synchronized boolean hasAcquiredIndexCommitsForTesting() {
     /**
      * Checks if the deletion policy can delete some index commits with the latest global checkpoint.
      */
-    boolean hasUnreferencedCommits() {
+    @Override
+    public boolean hasUnreferencedCommits() {
         return maxSeqNoOfNextSafeCommit <= globalCheckpointSupplier.getAsLong();
     }
 

server/src/main/java/org/elasticsearch/index/engine/ElasticsearchIndexDeletionPolicy.java

@@ -0,0 +1,49 @@
+/*
+ * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.index.engine;
+
+import org.apache.lucene.index.IndexCommit;
+import org.apache.lucene.index.IndexDeletionPolicy;
+
+import java.util.Set;
+
+public abstract class ElasticsearchIndexDeletionPolicy extends IndexDeletionPolicy {
+
+    /**
+     * Captures the most recent commit point or the most recent safe commit point.
+     * 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.
+     */
+    public abstract IndexCommit acquireIndexCommit(boolean acquiringSafeCommit);
+
+    /**
+     * Releases an index commit that was acquired by {@link #acquireIndexCommit(boolean)}.
+     *
+     * @return true if the acquired commit can be clean up.
+     */
+    public abstract boolean releaseIndexCommit(IndexCommit acquiredIndexCommit);
+
+    /**
+     * @return information about the safe commit
+     */
+    public abstract SafeCommitInfo getSafeCommitInfo();
+
+    public abstract boolean hasAcquiredIndexCommitsForTesting();
+
+    public abstract boolean hasUnreferencedCommits();
+
+    public interface CommitsListener {
+
+        void onNewAcquiredCommit(IndexCommit commit, Set<String> additionalFiles);
+
+        void onDeletedCommit(IndexCommit commit);
+    }
+}

server/src/main/java/org/elasticsearch/index/engine/EngineConfig.java

@@ -41,6 +41,7 @@
 import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
+import java.util.function.Function;
 import java.util.function.LongSupplier;
 import java.util.function.Supplier;
 
@@ -151,6 +152,11 @@ public Supplier<RetentionLeases> retentionLeasesSupplier() {
 
     private final MergeMetrics mergeMetrics;
 
+    /**
+     * Allows to pass an {@link ElasticsearchIndexDeletionPolicy} wrapper to egine implementations.
+     */
+    private final Function<ElasticsearchIndexDeletionPolicy, ElasticsearchIndexDeletionPolicy> indexDeletionPolicyWrapper;
+
     /**
      * Creates a new {@link org.elasticsearch.index.engine.EngineConfig}
      */
@@ -184,7 +190,8 @@ public EngineConfig(
         boolean promotableToPrimary,
         MapperService mapperService,
         EngineResetLock engineResetLock,
-        MergeMetrics mergeMetrics
+        MergeMetrics mergeMetrics,
+        Function<ElasticsearchIndexDeletionPolicy, ElasticsearchIndexDeletionPolicy> indexDeletionPolicyWrapper
     ) {
         this.shardId = shardId;
         this.indexSettings = indexSettings;
@@ -233,6 +240,7 @@ public EngineConfig(
         this.useCompoundFile = indexSettings.getSettings().getAsBoolean(USE_COMPOUND_FILE, true);
         this.engineResetLock = engineResetLock;
         this.mergeMetrics = mergeMetrics;
+        this.indexDeletionPolicyWrapper = indexDeletionPolicyWrapper;
     }
 
     /**
@@ -485,4 +493,11 @@ public EngineResetLock getEngineResetLock() {
     public MergeMetrics getMergeMetrics() {
         return mergeMetrics;
     }
+
+    /**
+     * @return an {@link ElasticsearchIndexDeletionPolicy} wrapper, to be use by engine implementations.
+     */
+    public Function<ElasticsearchIndexDeletionPolicy, ElasticsearchIndexDeletionPolicy> getIndexDeletionPolicyWrapper() {
+        return indexDeletionPolicyWrapper;
+    }
 }

server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java

@@ -170,7 +170,7 @@ public class InternalEngine extends Engine {
 
     private final LocalCheckpointTracker localCheckpointTracker;
 
-    private final CombinedDeletionPolicy combinedDeletionPolicy;
+    private final ElasticsearchIndexDeletionPolicy indexDeletionPolicy;
 
     // How many callers are currently requesting index throttling. Currently there are only two situations where we do this: when merges
     // are falling behind and when writing indexing buffer to disk is too slow. When this is 0, there is no throttling, else we throttle
@@ -277,13 +277,7 @@ public InternalEngine(EngineConfig engineConfig) {
                 this.totalDiskSpace = ByteSizeValue.of(Environment.getFileStore(translog.location()).getTotalSpace(), ByteSizeUnit.BYTES);
                 this.lastCommittedSegmentInfos = store.readLastCommittedSegmentsInfo();
                 this.softDeletesPolicy = newSoftDeletesPolicy();
-                this.combinedDeletionPolicy = new CombinedDeletionPolicy(
-                    logger,
-                    translogDeletionPolicy,
-                    softDeletesPolicy,
-                    translog::getLastSyncedGlobalCheckpoint,
-                    newCommitsListener()
-                );
+                this.indexDeletionPolicy = newIndexDeletionPolicy(engineConfig, logger, translog, softDeletesPolicy);
                 this.localCheckpointTracker = createLocalCheckpointTracker(localCheckpointTrackerSupplier);
                 writer = createWriter();
                 bootstrapAppendOnlyInfoFromWriter(writer);
@@ -391,6 +385,25 @@ private SoftDeletesPolicy newSoftDeletesPolicy() throws IOException {
         );
     }
 
+    protected ElasticsearchIndexDeletionPolicy newIndexDeletionPolicy(
+        EngineConfig engineConfig,
+        Logger logger,
+        Translog translog,
+        SoftDeletesPolicy softDeletesPolicy
+    ) {
+        var wrapper = engineConfig.getIndexDeletionPolicyWrapper();
+        assert wrapper != null : "no index deletion policy wrapper for " + engineConfig.getShardId();
+        return wrapper.apply(
+            new CombinedDeletionPolicy(
+                logger,
+                translog.getDeletionPolicy(),
+                softDeletesPolicy,
+                translog::getLastSyncedGlobalCheckpoint,
+                newCommitsListener()
+            )
+        );
+    }
+
     @Nullable
     private CombinedDeletionPolicy.CommitsListener newCommitsListener() {
         IndexCommitListener listener = engineConfig.getIndexCommitListener();
@@ -682,7 +695,7 @@ Translog getTranslog() {
 
     // Package private for testing purposes only
     boolean hasAcquiredIndexCommitsForTesting() {
-        return combinedDeletionPolicy.hasAcquiredIndexCommitsForTesting();
+        return indexDeletionPolicy.hasAcquiredIndexCommitsForTesting();
     }
 
     @Override
@@ -748,7 +761,7 @@ public Translog.Location getTranslogLastWriteLocation() {
     }
 
     private void revisitIndexDeletionPolicyOnTranslogSynced() throws IOException {
-        if (combinedDeletionPolicy.hasUnreferencedCommits()) {
+        if (indexDeletionPolicy.hasUnreferencedCommits()) {
             indexWriter.deleteUnusedFiles();
         }
         translog.trimUnreferencedReaders();
@@ -2555,17 +2568,17 @@ public IndexCommitRef acquireLastIndexCommit(final boolean flushFirst) throws En
             future.actionGet();
             logger.trace("finish flush for snapshot");
         }
-        return acquireIndexCommitRef(() -> combinedDeletionPolicy.acquireIndexCommit(false));
+        return acquireIndexCommitRef(() -> indexDeletionPolicy.acquireIndexCommit(false));
     }
 
     @Override
     public IndexCommitRef acquireSafeIndexCommit() throws EngineException {
-        return acquireIndexCommitRef(() -> combinedDeletionPolicy.acquireIndexCommit(true));
+        return acquireIndexCommitRef(() -> indexDeletionPolicy.acquireIndexCommit(true));
     }
 
     private void releaseIndexCommit(IndexCommit snapshot) throws IOException {
         // Revisit the deletion policy if we can clean up the snapshotting commit.
-        if (combinedDeletionPolicy.releaseCommit(snapshot)) {
+        if (indexDeletionPolicy.releaseIndexCommit(snapshot)) {
             try {
                 // Here we don't have to trim translog because snapshotting an index commit
                 // does not lock translog or prevents unreferenced files from trimming.
@@ -2578,7 +2591,7 @@ private void releaseIndexCommit(IndexCommit snapshot) throws IOException {
 
     @Override
     public SafeCommitInfo getSafeCommitInfo() {
-        return combinedDeletionPolicy.getSafeCommitInfo();
+        return indexDeletionPolicy.getSafeCommitInfo();
     }
 
     private boolean failOnTragicEvent(AlreadyClosedException ex) {
@@ -2756,7 +2769,7 @@ private IndexWriterConfig getIndexWriterConfig() {
         final IndexWriterConfig iwc = new IndexWriterConfig(engineConfig.getAnalyzer());
         iwc.setCommitOnClose(false); // we by default don't commit on close
         iwc.setOpenMode(IndexWriterConfig.OpenMode.APPEND);
-        iwc.setIndexDeletionPolicy(combinedDeletionPolicy);
+        iwc.setIndexDeletionPolicy(indexDeletionPolicy);
         iwc.setInfoStream(TESTS_VERBOSE ? InfoStream.getDefault() : new LoggerInfoStream(logger));
         iwc.setMergeScheduler(mergeScheduler.getMergeScheduler());
         // Give us the opportunity to upgrade old segments while performing

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -3765,7 +3765,8 @@ private EngineConfig newEngineConfig(LongSupplier globalCheckpointSupplier) {
             routingEntry().isPromotableToPrimary(),
             mapperService(),
             engineResetLock,
-            mergeMetrics
+            mergeMetrics,
+            Function.identity()
         );
     }
 

server/src/test/java/org/elasticsearch/index/engine/CombinedDeletionPolicyTests.java

@@ -193,7 +193,7 @@ public void testAcquireIndexCommit() throws Exception {
                 final IndexCommit lastCommit = commitList.get(commitList.size() - 1);
                 safeCommit = CombinedDeletionPolicy.findSafeCommitPoint(commitList, globalCheckpoint.get());
                 assertThat(
-                    indexPolicy.releaseCommit(snapshot),
+                    indexPolicy.releaseIndexCommit(snapshot),
                     equalTo(pendingSnapshots == 0 && snapshot.equals(lastCommit) == false && snapshot.equals(safeCommit) == false)
                 );
             }
@@ -211,7 +211,7 @@ public void testAcquireIndexCommit() throws Exception {
                 )
             );
         }
-        snapshottingCommits.forEach(indexPolicy::releaseCommit);
+        snapshottingCommits.forEach(indexPolicy::releaseIndexCommit);
         globalCheckpoint.set(randomLongBetween(lastMaxSeqNo, Long.MAX_VALUE));
         commitList.forEach(this::resetDeletion);
         indexPolicy.onCommit(commitList);
@@ -350,8 +350,8 @@ protected int getDocCountOfCommit(IndexCommit indexCommit) {
             }
 
             @Override
-            synchronized boolean releaseCommit(IndexCommit acquiredCommit) {
-                return super.releaseCommit(wrapCommit(acquiredCommit));
+            public synchronized boolean releaseIndexCommit(IndexCommit acquiredCommit) {
+                return super.releaseIndexCommit(wrapCommit(acquiredCommit));
             }
         };
 
@@ -383,7 +383,7 @@ synchronized boolean releaseCommit(IndexCommit acquiredCommit) {
         assertThat(deletedCommits, hasSize(0));
         assertThat(newCommitFiles, containsInAnyOrder(equalTo("_1.cfe"), equalTo("_1.si"), equalTo("_1.cfs"), equalTo("segments_2")));
 
-        boolean maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit0);
+        boolean maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit0);
         assertThat(maybeCleanUpCommits, equalTo(true));
 
         globalCheckpoint.set(20L);
@@ -454,7 +454,7 @@ synchronized boolean releaseCommit(IndexCommit acquiredCommit) {
             )
         );
 
-        maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit2);
+        maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit2);
         assertThat("No commits to clean up (commit #2 is the safe commit)", maybeCleanUpCommits, equalTo(false));
 
         globalCheckpoint.set(30L);
@@ -499,13 +499,13 @@ synchronized boolean releaseCommit(IndexCommit acquiredCommit) {
         assertThat(deletedCommits, contains(commit0, commit2));
         assertThat(newCommitFiles, containsInAnyOrder(equalTo("_4.cfe"), equalTo("_4.si"), equalTo("_4.cfs"), equalTo("segments_4")));
 
-        maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit3);
+        maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit3);
         assertThat("No commits to clean up (commit #3 is the safe commit)", maybeCleanUpCommits, equalTo(false));
 
-        maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit4);
+        maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit4);
         assertThat("No commits to clean up (commit #4 is the last commit)", maybeCleanUpCommits, equalTo(false));
 
-        maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit1);
+        maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit1);
         assertThat(maybeCleanUpCommits, equalTo(true));
 
         final boolean globalCheckpointCatchUp = randomBoolean();
@@ -560,7 +560,7 @@ synchronized boolean releaseCommit(IndexCommit acquiredCommit) {
         }
         assertThat(newCommitFiles, containsInAnyOrder(equalTo("_5.cfe"), equalTo("_5.si"), equalTo("_5.cfs"), equalTo("segments_5")));
 
-        maybeCleanUpCommits = combinedDeletionPolicy.releaseCommit(commit5);
+        maybeCleanUpCommits = combinedDeletionPolicy.releaseIndexCommit(commit5);
         assertThat("No commits to clean up (commit #5 is the last commit)", maybeCleanUpCommits, equalTo(false));
     }