Use Lucene soft-deletes in peer recovery (#30522)

This commit adds Lucene soft-deletes as another source for peer-recovery
besides translog.

Relates #29530

docs/reference/indices/flush.asciidoc

@@ -101,7 +101,8 @@ which returns something similar to:
                      "translog_generation" : "2",
                      "max_seq_no" : "-1",
                      "sync_id" : "AVvFY-071siAOuFGEO9P", <1>
-                     "max_unsafe_auto_id_timestamp" : "-1"
+                     "max_unsafe_auto_id_timestamp" : "-1",
+                     "min_retained_seq_no": "0"
                    },
                    "num_docs" : 0
                  }

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

@@ -46,14 +46,17 @@
 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<IndexCommit> 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, LongSupplier globalCheckpointSupplier) {
+    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<>();
     }
@@ -80,7 +83,7 @@ public synchronized void onCommit(List<? extends IndexCommit> commits) throws IO
                 deleteCommit(commits.get(i));
             }
         }
-        updateTranslogDeletionPolicy();
+        updateRetentionPolicy();
     }
 
     private void deleteCommit(IndexCommit commit) throws IOException {
@@ -90,7 +93,7 @@ private void deleteCommit(IndexCommit commit) throws IOException {
         assert commit.isDeleted() : "Deletion commit [" + commitDescription(commit) + "] was suppressed";
     }
 
-    private void updateTranslogDeletionPolicy() throws IOException {
+    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";
@@ -101,6 +104,9 @@ private void updateTranslogDeletionPolicy() throws IOException {
         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)));
     }
 
     /**

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

@@ -98,6 +98,7 @@ public abstract class Engine implements Closeable {
 
     public static final String SYNC_COMMIT_ID = "sync_id";
     public static final String HISTORY_UUID_KEY = "history_uuid";
+    public static final String MIN_RETAINED_SEQNO = "min_retained_seq_no";
 
     protected final ShardId shardId;
     protected final String allocationId;
@@ -578,19 +579,17 @@ public enum SearcherScope {
 
     public abstract void syncTranslog() throws IOException;
 
-    public abstract Closeable acquireTranslogRetentionLock();
+    /**
+     * Acquires a lock on the translog files and Lucene soft-deleted documents to prevent them from being trimmed
+     */
+    public abstract Closeable acquireRetentionLockForPeerRecovery();
 
     /**
      * Creates a new translog snapshot from this engine for reading translog operations whose seq# in the provided range.
      * The caller has to close the returned snapshot after finishing the reading.
      */
     public abstract Translog.Snapshot newTranslogSnapshotBetween(long minSeqNo, long maxSeqNo) throws IOException;
 
-    /**
-     * Returns the estimated number of translog operations in this engine whose seq# at least the provided seq#.
-     */
-    public abstract int estimateTranslogOperationsFromMinSeq(long minSeqNo);
-
     public abstract TranslogStats getTranslogStats();
 
     /**
@@ -604,6 +603,19 @@ public enum SearcherScope {
     public abstract Translog.Snapshot newLuceneChangesSnapshot(String source, MapperService mapperService,
                                                                long minSeqNo, long maxSeqNo, boolean requiredFullRange) throws IOException;
 
+    /**
+     * Creates a new history snapshot for reading operations since the provided seqno.
+     * The returned snapshot can be retrieved from either Lucene index or translog files.
+     */
+    public abstract Translog.Snapshot readHistoryOperations(String source, MapperService mapperService, long startingSeqNo) throws IOException;
+
+    /**
+     * Returns the estimated number of history operations whose seq# at least the provided seq# in this engine.
+     */
+    public abstract int estimateNumberOfHistoryOperations(String source, MapperService mapperService, long startingSeqNo) throws IOException;
+
+    public abstract boolean hasCompleteOperationHistory(String source, MapperService mapperService, long startingSeqNo) throws IOException;
+
     protected final void ensureOpen(Exception suppressed) {
         if (isClosed.get()) {
             AlreadyClosedException ace = new AlreadyClosedException(shardId + " engine is closed", failedEngine.get());

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

@@ -22,7 +22,6 @@
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.message.ParameterizedMessage;
 import org.apache.lucene.document.Field;
-import org.apache.lucene.document.LongPoint;
 import org.apache.lucene.document.NumericDocValuesField;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexCommit;
@@ -38,7 +37,6 @@
 import org.apache.lucene.index.SoftDeletesRetentionMergePolicy;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.IndexSearcher;
-import org.apache.lucene.search.Query;
 import org.apache.lucene.search.ReferenceManager;
 import org.apache.lucene.search.SearcherFactory;
 import org.apache.lucene.search.SearcherManager;
@@ -157,6 +155,7 @@ public class InternalEngine extends Engine {
     private final CounterMetric numDocUpdates = new CounterMetric();
     private final NumericDocValuesField softDeleteField = Lucene.newSoftDeleteField();
     private final boolean softDeleteEnabled;
+    private final SoftDeletesPolicy softDeletesPolicy;
     private final LastRefreshedCheckpointListener lastRefreshedCheckpointListener;
 
     /**
@@ -182,7 +181,6 @@ public InternalEngine(EngineConfig engineConfig) {
             maxUnsafeAutoIdTimestamp.set(Long.MAX_VALUE);
         }
         this.uidField = engineConfig.getIndexSettings().isSingleType() ? IdFieldMapper.NAME : UidFieldMapper.NAME;
-        this.softDeleteEnabled = engineConfig.getIndexSettings().isSoftDeleteEnabled();
         final TranslogDeletionPolicy translogDeletionPolicy = new TranslogDeletionPolicy(
                 engineConfig.getIndexSettings().getTranslogRetentionSize().getBytes(),
                 engineConfig.getIndexSettings().getTranslogRetentionAge().getMillis()
@@ -204,8 +202,10 @@ public InternalEngine(EngineConfig engineConfig) {
                 assert translog.getGeneration() != null;
                 this.translog = translog;
                 this.localCheckpointTracker = createLocalCheckpointTracker(localCheckpointTrackerSupplier);
+                this.softDeleteEnabled = engineConfig.getIndexSettings().isSoftDeleteEnabled();
+                this.softDeletesPolicy = newSoftDeletesPolicy();
                 this.combinedDeletionPolicy =
-                    new CombinedDeletionPolicy(logger, translogDeletionPolicy, translog::getLastSyncedGlobalCheckpoint);
+                    new CombinedDeletionPolicy(logger, translogDeletionPolicy, softDeletesPolicy, translog::getLastSyncedGlobalCheckpoint);
                 writer = createWriter();
                 bootstrapAppendOnlyInfoFromWriter(writer);
                 historyUUID = loadHistoryUUID(writer);
@@ -262,6 +262,18 @@ private LocalCheckpointTracker createLocalCheckpointTracker(
         return localCheckpointTrackerSupplier.apply(maxSeqNo, localCheckpoint);
     }
 
+    private SoftDeletesPolicy newSoftDeletesPolicy() throws IOException {
+        final Map<String, String> commitUserData = store.readLastCommittedSegmentsInfo().userData;
+        final long lastMinRetainedSeqNo;
+        if (commitUserData.containsKey(Engine.MIN_RETAINED_SEQNO)) {
+            lastMinRetainedSeqNo = Long.parseLong(commitUserData.get(Engine.MIN_RETAINED_SEQNO));
+        } else {
+            lastMinRetainedSeqNo = Long.parseLong(commitUserData.get(SequenceNumbers.MAX_SEQ_NO)) + 1;
+        }
+        return new SoftDeletesPolicy(translog::getLastSyncedGlobalCheckpoint, lastMinRetainedSeqNo,
+            engineConfig.getIndexSettings().getSoftDeleteRetentionOperations());
+    }
+
     /**
      * This reference manager delegates all it's refresh calls to another (internal) SearcherManager
      * The main purpose for this is that if we have external refreshes happening we don't issue extra
@@ -481,18 +493,39 @@ public void syncTranslog() throws IOException {
     }
 
     @Override
-    public Closeable acquireTranslogRetentionLock() {
-        return getTranslog().acquireRetentionLock();
+    public Translog.Snapshot newTranslogSnapshotBetween(long minSeqNo, long maxSeqNo) throws IOException {
+        return getTranslog().getSnapshotBetween(minSeqNo, maxSeqNo);
     }
 
+    /**
+     * Creates a new history snapshot for reading operations since the provided seqno.
+     * The returned snapshot can be retrieved from either Lucene index or translog files.
+     */
     @Override
-    public Translog.Snapshot newTranslogSnapshotBetween(long minSeqNo, long maxSeqNo) throws IOException {
-        return getTranslog().getSnapshotBetween(minSeqNo, maxSeqNo);
+    public Translog.Snapshot readHistoryOperations(String source, MapperService mapperService, long startingSeqNo) throws IOException {
+        if (engineConfig.getIndexSettings().isSoftDeleteEnabled()) {
+            return newLuceneChangesSnapshot(source, mapperService, Math.max(0, startingSeqNo), Long.MAX_VALUE, false);
+        } else {
+            return getTranslog().getSnapshotBetween(startingSeqNo, Long.MAX_VALUE);
+        }
     }
 
+    /**
+     * Returns the estimated number of history operations whose seq# at least the provided seq# in this engine.
+     */
     @Override
-    public int estimateTranslogOperationsFromMinSeq(long minSeqNo) {
-        return getTranslog().estimateTotalOperationsFromMinSeq(minSeqNo);
+    public int estimateNumberOfHistoryOperations(String source, MapperService mapperService, long startingSeqNo) throws IOException {
+        if (engineConfig.getIndexSettings().isSoftDeleteEnabled()) {
+            try (Translog.Snapshot snapshot =
+                     newLuceneChangesSnapshot(source, mapperService, Math.max(0, startingSeqNo), Long.MAX_VALUE, false)) {
+                return snapshot.totalOperations();
+            } catch (IOException ex) {
+                maybeFailEngine(source, ex);
+                throw ex;
+            }
+        } else {
+            return getTranslog().estimateTotalOperationsFromMinSeq(startingSeqNo);
+        }
     }
 
     @Override
@@ -2127,8 +2160,8 @@ private IndexWriterConfig getIndexWriterConfig() {
         MergePolicy mergePolicy = config().getMergePolicy();
         if (softDeleteEnabled) {
             iwc.setSoftDeletesField(Lucene.SOFT_DELETE_FIELD);
-            mergePolicy = new RecoverySourcePruneMergePolicy(SourceFieldMapper.RECOVERY_SOURCE_NAME, this::softDeletesRetentionQuery,
-                new SoftDeletesRetentionMergePolicy(Lucene.SOFT_DELETE_FIELD, this::softDeletesRetentionQuery, mergePolicy));
+            mergePolicy = new RecoverySourcePruneMergePolicy(SourceFieldMapper.RECOVERY_SOURCE_NAME, softDeletesPolicy::getRetentionQuery,
+                new SoftDeletesRetentionMergePolicy(Lucene.SOFT_DELETE_FIELD, softDeletesPolicy::getRetentionQuery, mergePolicy));
         }
         iwc.setMergePolicy(new ElasticsearchMergePolicy(mergePolicy));
         iwc.setSimilarity(engineConfig.getSimilarity());
@@ -2141,20 +2174,6 @@ private IndexWriterConfig getIndexWriterConfig() {
         return iwc;
     }
 
-    /**
-     * Documents including tombstones are soft-deleted and matched this query will be retained and won't cleaned up by merges.
-     */
-    private Query softDeletesRetentionQuery() {
-        ensureOpen();
-        // TODO: We send the safe commit in peer-recovery, thus we need to retain all operations after the local checkpoint of that commit.
-        final long retainedExtraOps = engineConfig.getIndexSettings().getSoftDeleteRetentionOperations();
-        // Prefer using the global checkpoint which is persisted on disk than an in-memory value.
-        // If we failed to fsync checkpoint but already used a higher global checkpoint value to clean up soft-deleted ops,
-        // then we may not have all required operations whose seq# greater than the global checkpoint after restarted.
-        final long persistedGlobalCheckpoint = translog.getLastSyncedGlobalCheckpoint();
-        return LongPoint.newRangeQuery(SeqNoFieldMapper.NAME, persistedGlobalCheckpoint + 1 - retainedExtraOps, Long.MAX_VALUE);
-    }
-
     /** Extended SearcherFactory that warms the segments if needed when acquiring a new searcher */
     static final class SearchFactory extends EngineSearcherFactory {
         private final Engine.Warmer warmer;
@@ -2341,6 +2360,9 @@ protected void commitIndexWriter(final IndexWriter writer, final Translog transl
                 commitData.put(SequenceNumbers.MAX_SEQ_NO, Long.toString(localCheckpointTracker.getMaxSeqNo()));
                 commitData.put(MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, Long.toString(maxUnsafeAutoIdTimestamp.get()));
                 commitData.put(HISTORY_UUID_KEY, historyUUID);
+                if (softDeleteEnabled) {
+                    commitData.put(Engine.MIN_RETAINED_SEQNO, Long.toString(softDeletesPolicy.getMinRetainedSeqNo()));
+                }
                 logger.trace("committing writer with commit data [{}]", commitData);
                 return commitData.entrySet().iterator();
             });
@@ -2396,6 +2418,8 @@ public void onSettingsChanged() {
         final IndexSettings indexSettings = engineConfig.getIndexSettings();
         translogDeletionPolicy.setRetentionAgeInMillis(indexSettings.getTranslogRetentionAge().getMillis());
         translogDeletionPolicy.setRetentionSizeInBytes(indexSettings.getTranslogRetentionSize().getBytes());
+
+        softDeletesPolicy.setRetentionOperations(indexSettings.getSoftDeleteRetentionOperations());
     }
 
     public MergeStats getMergeStats() {
@@ -2509,6 +2533,41 @@ public Translog.Snapshot newLuceneChangesSnapshot(String source, MapperService m
         }
     }
 
+    @Override
+    public boolean hasCompleteOperationHistory(String source, MapperService mapperService, long startingSeqNo) throws IOException {
+        if (engineConfig.getIndexSettings().isSoftDeleteEnabled()) {
+            return getMinRetainedSeqNo() <= startingSeqNo;
+        } else {
+            final long currentLocalCheckpoint = getLocalCheckpointTracker().getCheckpoint();
+            final LocalCheckpointTracker tracker = new LocalCheckpointTracker(startingSeqNo, startingSeqNo - 1);
+            try (Translog.Snapshot snapshot = getTranslog().getSnapshotBetween(startingSeqNo, Long.MAX_VALUE)) {
+                Translog.Operation operation;
+                while ((operation = snapshot.next()) != null) {
+                    if (operation.seqNo() != SequenceNumbers.UNASSIGNED_SEQ_NO) {
+                        tracker.markSeqNoAsCompleted(operation.seqNo());
+                    }
+                }
+            }
+            return tracker.getCheckpoint() >= currentLocalCheckpoint;
+        }
+    }
+
+    /**
+     * Returns the minimum seqno that is retained in the Lucene index.
+     * Operations whose seq# are at least this value should exist in the Lucene index.
+     */
+    final long getMinRetainedSeqNo() {
+        assert softDeleteEnabled : Thread.currentThread().getName();
+        return softDeletesPolicy.getMinRetainedSeqNo();
+    }
+
+    @Override
+    public Closeable acquireRetentionLockForPeerRecovery() {
+        final Closeable translogLock = translog.acquireRetentionLock();
+        final Releasable softDeletesLock = softDeletesPolicy.acquireRetentionLock();
+        return () -> IOUtils.close(translogLock, softDeletesLock);
+    }
+
     @Override
     public boolean isRecovering() {
         return pendingTranslogRecovery.get();

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

@@ -116,7 +116,7 @@ public int totalOperations() {
     }
 
     @Override
-    public int overriddenOperations() {
+    public int skippedOperations() {
         return skippedOperations;
     }