Introduce retention lease state file (#39004)

This commit moves retention leases from being persisted in the Lucene
commit point to being persisted in a dedicated state file.

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

@@ -114,7 +114,6 @@ 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";
-    public static final String RETENTION_LEASES = "retention_leases";
     public static final String MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID = "max_unsafe_auto_id_timestamp";
 
     protected final ShardId shardId;

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

@@ -51,7 +51,6 @@
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.SuppressForbidden;
-import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.lease.Releasable;
 import org.elasticsearch.common.lucene.LoggerInfoStream;
 import org.elasticsearch.common.lucene.Lucene;
@@ -76,7 +75,6 @@
 import org.elasticsearch.index.merge.MergeStats;
 import org.elasticsearch.index.merge.OnGoingMerge;
 import org.elasticsearch.index.seqno.LocalCheckpointTracker;
-import org.elasticsearch.index.seqno.RetentionLeases;
 import org.elasticsearch.index.seqno.SeqNoStats;
 import org.elasticsearch.index.seqno.SequenceNumbers;
 import org.elasticsearch.index.shard.ElasticsearchMergePolicy;
@@ -2433,13 +2431,7 @@ protected void commitIndexWriter(final IndexWriter writer, final Translog transl
                 commitData.put(MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, Long.toString(maxUnsafeAutoIdTimestamp.get()));
                 commitData.put(HISTORY_UUID_KEY, historyUUID);
                 if (softDeleteEnabled) {
-                    /*
-                     * We sample these from the policy (which occurs under a lock) to ensure that we have a consistent view of the minimum
-                     * retained sequence number, and the retention leases.
-                     */
-                    final Tuple<Long, RetentionLeases> retentionPolicy = softDeletesPolicy.getRetentionPolicy();
-                    commitData.put(Engine.MIN_RETAINED_SEQNO, Long.toString(retentionPolicy.v1()));
-                    commitData.put(Engine.RETENTION_LEASES, RetentionLeases.encodeRetentionLeases(retentionPolicy.v2()));
+                    commitData.put(Engine.MIN_RETAINED_SEQNO, Long.toString(softDeletesPolicy.getMinRetainedSeqNo()));
                 }
                 logger.trace("committing writer with commit data [{}]", commitData);
                 return commitData.entrySet().iterator();

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

@@ -21,7 +21,6 @@
 
 import org.apache.lucene.document.LongPoint;
 import org.apache.lucene.search.Query;
-import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.lease.Releasable;
 import org.elasticsearch.index.mapper.SeqNoFieldMapper;
 import org.elasticsearch.index.seqno.RetentionLease;
@@ -107,10 +106,6 @@ private synchronized void releaseRetentionLock() {
      * Operations whose seq# is least this value should exist in the Lucene index.
      */
     synchronized long getMinRetainedSeqNo() {
-        return getRetentionPolicy().v1();
-    }
-
-    public synchronized Tuple<Long, RetentionLeases> getRetentionPolicy() {
         /*
          * When an engine is flushed, we need to provide it the latest collection of retention leases even when the soft deletes policy is
          * locked for peer recovery.
@@ -151,7 +146,7 @@ public synchronized Tuple<Long, RetentionLeases> getRetentionPolicy() {
              */
             minRetainedSeqNo = Math.max(minRetainedSeqNo, minSeqNoToRetain);
         }
-        return Tuple.tuple(minRetainedSeqNo, retentionLeases);
+        return minRetainedSeqNo;
     }
 
     /**

server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java

@@ -32,13 +32,15 @@
 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.xcontent.NamedXContentRegistry;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.shard.AbstractIndexShardComponent;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.shard.ReplicationGroup;
 import org.elasticsearch.index.shard.ShardId;
 
 import java.io.IOException;
+import java.nio.file.Path;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
@@ -318,6 +320,40 @@ public synchronized void updateRetentionLeasesOnReplica(final RetentionLeases re
         }
     }
 
+    /**
+     * Loads the latest retention leases from their dedicated state file.
+     *
+     * @param path the path to the directory containing the state file
+     * @return the retention leases
+     * @throws IOException if an I/O exception occurs reading the retention leases
+     */
+    public RetentionLeases loadRetentionLeases(final Path path) throws IOException {
+        final RetentionLeases retentionLeases = RetentionLeases.FORMAT.loadLatestState(logger, NamedXContentRegistry.EMPTY, path);
+        if (retentionLeases == null) {
+            return RetentionLeases.EMPTY;
+        }
+        return retentionLeases;
+    }
+
+    private final Object retentionLeasePersistenceLock = new Object();
+
+    /**
+     * Persists the current retention leases to their dedicated state file.
+     *
+     * @param path the path to the directory containing the state file
+     * @throws IOException if an exception occurs writing the state file
+     */
+    public void persistRetentionLeases(final Path path) throws IOException {
+        synchronized (retentionLeasePersistenceLock) {
+            final RetentionLeases currentRetentionLeases;
+            synchronized (this) {
+                currentRetentionLeases = retentionLeases;
+            }
+            logger.trace("persisting retention leases [{}]", currentRetentionLeases);
+            RetentionLeases.FORMAT.write(currentRetentionLeases, path);
+        }
+    }
+
     public static class CheckpointState implements Writeable {
 
         /**

server/src/main/java/org/elasticsearch/index/seqno/RetentionLease.java

@@ -19,13 +19,16 @@
 
 package org.elasticsearch.index.seqno;
 
+import org.elasticsearch.common.ParseField;
 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.xcontent.ConstructingObjectParser;
+import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentParser;
 
 import java.io.IOException;
-import java.util.Arrays;
-import java.util.Locale;
 import java.util.Objects;
 
 /**
@@ -34,7 +37,7 @@
  * otherwise merge away operations that have been soft deleted). Each retention lease contains a unique identifier, the retaining sequence
  * number, the timestamp of when the lease was created or renewed, and the source of the retention lease (e.g., "ccr").
  */
-public final class RetentionLease implements Writeable {
+public final class RetentionLease implements ToXContent, Writeable {
 
     private final String id;
 
@@ -94,10 +97,6 @@ public RetentionLease(final String id, final long retainingSequenceNumber, final
         if (id.isEmpty()) {
             throw new IllegalArgumentException("retention lease ID can not be empty");
         }
-        if (id.contains(":") || id.contains(";") || id.contains(",")) {
-            // retention lease IDs can not contain these characters because they are used in encoding retention leases
-            throw new IllegalArgumentException("retention lease ID can not contain any of [:;,] but was [" + id + "]");
-        }
         if (retainingSequenceNumber < 0) {
             throw new IllegalArgumentException("retention lease retaining sequence number [" + retainingSequenceNumber + "] out of range");
         }
@@ -108,10 +107,6 @@ public RetentionLease(final String id, final long retainingSequenceNumber, final
         if (source.isEmpty()) {
             throw new IllegalArgumentException("retention lease source can not be empty");
         }
-        if (source.contains(":") || source.contains(";") || source.contains(",")) {
-            // retention lease sources can not contain these characters because they are used in encoding retention leases
-            throw new IllegalArgumentException("retention lease source can not contain any of [:;,] but was [" + source + "]");
-        }
         this.id = id;
         this.retainingSequenceNumber = retainingSequenceNumber;
         this.timestamp = timestamp;
@@ -145,43 +140,49 @@ public void writeTo(final StreamOutput out) throws IOException {
         out.writeString(source);
     }
 
-    /**
-     * Encodes a retention lease as a string. This encoding can be decoded by {@link #decodeRetentionLease(String)}. The retention lease is
-     * encoded in the format <code>id:{id};retaining_seq_no:{retainingSequenecNumber};timestamp:{timestamp};source:{source}</code>.
-     *
-     * @param retentionLease the retention lease
-     * @return the encoding of the retention lease
-     */
-    static String encodeRetentionLease(final RetentionLease retentionLease) {
-        Objects.requireNonNull(retentionLease);
-        return String.format(
-                Locale.ROOT,
-                "id:%s;retaining_seq_no:%d;timestamp:%d;source:%s",
-                retentionLease.id,
-                retentionLease.retainingSequenceNumber,
-                retentionLease.timestamp,
-                retentionLease.source);
+    private static final ParseField ID_FIELD = new ParseField("id");
+    private static final ParseField RETAINING_SEQUENCE_NUMBER_FIELD = new ParseField("retaining_sequence_number");
+    private static final ParseField TIMESTAMP_FIELD = new ParseField("timestamp");
+    private static final ParseField SOURCE_FIELD = new ParseField("source");
+
+    private static ConstructingObjectParser<RetentionLease, Void> PARSER = new ConstructingObjectParser<>(
+            "retention_leases",
+            (a) -> new RetentionLease((String) a[0], (Long) a[1], (Long) a[2], (String) a[3]));
+
+    static {
+        PARSER.declareString(ConstructingObjectParser.constructorArg(), ID_FIELD);
+        PARSER.declareLong(ConstructingObjectParser.constructorArg(), RETAINING_SEQUENCE_NUMBER_FIELD);
+        PARSER.declareLong(ConstructingObjectParser.constructorArg(), TIMESTAMP_FIELD);
+        PARSER.declareString(ConstructingObjectParser.constructorArg(), SOURCE_FIELD);
+    }
+
+    @Override
+    public XContentBuilder toXContent(final XContentBuilder builder, final Params params) throws IOException {
+        builder.startObject();
+        {
+            builder.field(ID_FIELD.getPreferredName(), id);
+            builder.field(RETAINING_SEQUENCE_NUMBER_FIELD.getPreferredName(), retainingSequenceNumber);
+            builder.field(TIMESTAMP_FIELD.getPreferredName(), timestamp);
+            builder.field(SOURCE_FIELD.getPreferredName(), source);
+        }
+        builder.endObject();
+        return builder;
+    }
+
+    @Override
+    public boolean isFragment() {
+        return false;
     }
 
     /**
-     * Decodes a retention lease encoded by {@link #encodeRetentionLease(RetentionLease)}.
+     * Parses a retention lease from {@link org.elasticsearch.common.xcontent.XContent}. This method assumes that the retention lease was
+     * converted to {@link org.elasticsearch.common.xcontent.XContent} via {@link #toXContent(XContentBuilder, Params)}.
      *
-     * @param encodedRetentionLease an encoded retention lease
-     * @return the decoded retention lease
+     * @param parser the parser
+     * @return a retention lease
      */
-    static RetentionLease decodeRetentionLease(final String encodedRetentionLease) {
-        Objects.requireNonNull(encodedRetentionLease);
-        final String[] fields = encodedRetentionLease.split(";");
-        assert fields.length == 4 : Arrays.toString(fields);
-        assert fields[0].matches("id:[^:;,]+") : fields[0];
-        final String id = fields[0].substring("id:".length());
-        assert fields[1].matches("retaining_seq_no:\\d+") : fields[1];
-        final long retainingSequenceNumber = Long.parseLong(fields[1].substring("retaining_seq_no:".length()));
-        assert fields[2].matches("timestamp:\\d+") : fields[2];
-        final long timestamp = Long.parseLong(fields[2].substring("timestamp:".length()));
-        assert fields[3].matches("source:[^:;,]+") : fields[3];
-        final String source = fields[3].substring("source:".length());
-        return new RetentionLease(id, retainingSequenceNumber, timestamp, source);
+    public static RetentionLease fromXContent(final XContentParser parser) {
+        return PARSER.apply(parser, null);
     }
 
     @Override

server/src/main/java/org/elasticsearch/index/seqno/RetentionLeaseBackgroundSyncAction.java

@@ -119,19 +119,21 @@ public void backgroundSync(
     }
 
     @Override
-    protected PrimaryResult<Request, ReplicationResponse> shardOperationOnPrimary(final Request request, final IndexShard primary) {
+    protected PrimaryResult<Request, ReplicationResponse> shardOperationOnPrimary(
+            final Request request,
+            final IndexShard primary) throws IOException {
         Objects.requireNonNull(request);
         Objects.requireNonNull(primary);
-        primary.afterWriteOperation();
+        primary.persistRetentionLeases();
         return new PrimaryResult<>(request, new ReplicationResponse());
     }
 
     @Override
-    protected ReplicaResult shardOperationOnReplica(final Request request, final IndexShard replica){
+    protected ReplicaResult shardOperationOnReplica(final Request request, final IndexShard replica) throws IOException {
         Objects.requireNonNull(request);
         Objects.requireNonNull(replica);
         replica.updateRetentionLeasesOnReplica(request.getRetentionLeases());
-        replica.afterWriteOperation();
+        replica.persistRetentionLeases();
         return new ReplicaResult();
     }
 

server/src/main/java/org/elasticsearch/index/seqno/RetentionLeaseSyncAction.java

@@ -25,7 +25,6 @@
 import org.apache.lucene.store.AlreadyClosedException;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.ActionListener;
-import org.elasticsearch.action.admin.indices.flush.FlushRequest;
 import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.action.support.WriteResponse;
 import org.elasticsearch.action.support.replication.ReplicatedWriteRequest;
@@ -121,31 +120,26 @@ public void sync(
     }
 
     @Override
-    protected WritePrimaryResult<Request, Response> shardOperationOnPrimary(final Request request, final IndexShard primary) {
+    protected WritePrimaryResult<Request, Response> shardOperationOnPrimary(
+            final Request request,
+            final IndexShard primary) throws IOException {
         Objects.requireNonNull(request);
         Objects.requireNonNull(primary);
-        // we flush to ensure that retention leases are committed
-        flush(primary);
+        primary.persistRetentionLeases();
         return new WritePrimaryResult<>(request, new Response(), null, null, primary, logger);
     }
 
     @Override
-    protected WriteReplicaResult<Request> shardOperationOnReplica(final Request request, final IndexShard replica) {
+    protected WriteReplicaResult<Request> shardOperationOnReplica(
+            final Request request,
+            final IndexShard replica) throws IOException {
         Objects.requireNonNull(request);
         Objects.requireNonNull(replica);
         replica.updateRetentionLeasesOnReplica(request.getRetentionLeases());
-        // we flush to ensure that retention leases are committed
-        flush(replica);
+        replica.persistRetentionLeases();
         return new WriteReplicaResult<>(request, null, null, replica, logger);
     }
 
-    private void flush(final IndexShard indexShard) {
-        final FlushRequest flushRequest = new FlushRequest();
-        flushRequest.force(true);
-        flushRequest.waitIfOngoing(true);
-        indexShard.flush(flushRequest);
-    }
-
     public static final class Request extends ReplicatedWriteRequest<Request> {
 
         private RetentionLeases retentionLeases;