Statically cache the most common instances of o.e.a.support.replicati…

…on.ReplicationResponse.ShardInfo (#104571)

Interestingly enough, these instances account for more than 1% of
allocations even when there's no failures during the http_logs benchmark
indexing step (on coordinating/data nodes). => I think it's worthwhile
to make these immutable and precompute the most common ones (up to 9
replicas is probably overkill but these are cheap enough for it to be
irrelevant).

server/src/main/java/org/elasticsearch/action/bulk/BulkPrimaryExecutionContext.java

@@ -293,7 +293,7 @@ public void markOperationAsExecuted(Engine.Result result) {
                 }
                 executionResult = BulkItemResponse.success(current.id(), current.request().opType(), response);
                 // set a blank ShardInfo so we can safely send it to the replicas. We won't use it in the real response though.
-                executionResult.getResponse().setShardInfo(new ReplicationResponse.ShardInfo());
+                executionResult.getResponse().setShardInfo(ReplicationResponse.ShardInfo.EMPTY);
                 locationToSync = TransportWriteAction.locationToSync(locationToSync, result.getTranslogLocation());
             }
             case FAILURE -> {

server/src/main/java/org/elasticsearch/action/ingest/SimulateIndexResponse.java

@@ -9,7 +9,6 @@
 package org.elasticsearch.action.ingest;
 
 import org.elasticsearch.action.index.IndexResponse;
-import org.elasticsearch.action.support.replication.ReplicationResponse;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -36,7 +35,7 @@ public SimulateIndexResponse(StreamInput in) throws IOException {
         super(in);
         this.source = in.readBytesReference();
         this.sourceXContentType = XContentType.valueOf(in.readString());
-        setShardInfo(new ReplicationResponse.ShardInfo(0, 0));
+        setShardInfo(ShardInfo.EMPTY);
     }
 
     @SuppressWarnings("this-escape")
@@ -52,7 +51,7 @@ public SimulateIndexResponse(
         super(new ShardId(index, "", 0), id == null ? "<n/a>" : id, 0, 0, version, true, pipelines);
         this.source = source;
         this.sourceXContentType = sourceXContentType;
-        setShardInfo(new ReplicationResponse.ShardInfo(0, 0));
+        setShardInfo(ShardInfo.EMPTY);
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/support/replication/ReplicationOperation.java

@@ -466,14 +466,13 @@ private void decPendingAndFinishIfNeeded() {
 
     private void finish() {
         if (finished.compareAndSet(false, true)) {
-            final ReplicationResponse.ShardInfo.Failure[] failuresArray;
-            if (shardReplicaFailures.isEmpty()) {
-                failuresArray = ReplicationResponse.NO_FAILURES;
-            } else {
-                failuresArray = new ReplicationResponse.ShardInfo.Failure[shardReplicaFailures.size()];
-                shardReplicaFailures.toArray(failuresArray);
-            }
-            primaryResult.setShardInfo(new ReplicationResponse.ShardInfo(totalShards.get(), successfulShards.get(), failuresArray));
+            primaryResult.setShardInfo(
+                ReplicationResponse.ShardInfo.of(
+                    totalShards.get(),
+                    successfulShards.get(),
+                    shardReplicaFailures.toArray(ReplicationResponse.NO_FAILURES)
+                )
+            );
             resultListener.onResponse(primaryResult);
         }
     }

server/src/main/java/org/elasticsearch/action/support/replication/ReplicationResponse.java

@@ -27,6 +27,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.IntStream;
 
 import static org.elasticsearch.common.xcontent.XContentParserUtils.ensureExpectedToken;
 
@@ -43,7 +44,7 @@ public ReplicationResponse() {}
 
     public ReplicationResponse(StreamInput in) throws IOException {
         super(in);
-        shardInfo = new ReplicationResponse.ShardInfo(in);
+        shardInfo = ReplicationResponse.ShardInfo.readFrom(in);
     }
 
     @Override
@@ -61,30 +62,61 @@ public void setShardInfo(ShardInfo shardInfo) {
 
     public static class ShardInfo implements Writeable, ToXContentObject {
 
+        // cache the most commonly used instances where all shard operations succeeded to save allocations on the transport layer
+        private static final ShardInfo[] COMMON_INSTANCES = IntStream.range(0, 10)
+            .mapToObj(i -> new ShardInfo(i, i, NO_FAILURES))
+            .toArray(ShardInfo[]::new);
+
+        public static final ShardInfo EMPTY = COMMON_INSTANCES[0];
+
         private static final String TOTAL = "total";
         private static final String SUCCESSFUL = "successful";
         private static final String FAILED = "failed";
         private static final String FAILURES = "failures";
 
-        private int total;
-        private int successful;
-        private Failure[] failures = ReplicationResponse.NO_FAILURES;
+        private final int total;
+        private final int successful;
+        private final Failure[] failures;
 
-        public ShardInfo() {}
-
-        public ShardInfo(StreamInput in) throws IOException {
-            total = in.readVInt();
-            successful = in.readVInt();
+        public static ShardInfo readFrom(StreamInput in) throws IOException {
+            int total = in.readVInt();
+            int successful = in.readVInt();
             int size = in.readVInt();
+
+            final Failure[] failures;
             if (size > 0) {
                 failures = new Failure[size];
                 for (int i = 0; i < size; i++) {
                     failures[i] = new Failure(in);
                 }
+            } else {
+                failures = NO_FAILURES;
+            }
+            return ShardInfo.of(total, successful, failures);
+        }
+
+        public static ShardInfo allSuccessful(int total) {
+            if (total < COMMON_INSTANCES.length) {
+                return COMMON_INSTANCES[total];
             }
+            return new ShardInfo(total, total, NO_FAILURES);
+        }
+
+        public static ShardInfo of(int total, int successful) {
+            if (total == successful) {
+                return allSuccessful(total);
+            }
+            return new ShardInfo(total, successful, ReplicationResponse.NO_FAILURES);
+        }
+
+        public static ShardInfo of(int total, int successful, Failure[] failures) {
+            if (failures.length == 0) {
+                return of(total, successful);
+            }
+            return new ShardInfo(total, successful, failures);
         }
 
-        public ShardInfo(int total, int successful, Failure... failures) {
+        private ShardInfo(int total, int successful, Failure[] failures) {
             assert total >= 0 && successful >= 0;
             this.total = total;
             this.successful = successful;
@@ -188,7 +220,7 @@ public static ShardInfo fromXContent(XContentParser parser) throws IOException {
             }
             Failure[] failures = ReplicationResponse.NO_FAILURES;
             if (failuresList != null) {
-                failures = failuresList.toArray(new Failure[failuresList.size()]);
+                failures = failuresList.toArray(ReplicationResponse.NO_FAILURES);
             }
             return new ShardInfo(total, successful, failures);
         }

server/src/main/java/org/elasticsearch/action/update/UpdateResponse.java

@@ -46,7 +46,7 @@ public UpdateResponse(StreamInput in) throws IOException {
      * For example: update script with operation set to none
      */
     public UpdateResponse(ShardId shardId, String id, long seqNo, long primaryTerm, long version, Result result) {
-        this(new ShardInfo(0, 0), shardId, id, seqNo, primaryTerm, version, result);
+        this(ShardInfo.EMPTY, shardId, id, seqNo, primaryTerm, version, result);
     }
 
     @SuppressWarnings("this-escape")

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexStateService.java

@@ -654,7 +654,7 @@ private void sendVerifyShardBeforeCloseRequest(
             if (shardRoutingTable.primaryShard().unassigned()) {
                 logger.debug("primary shard {} is unassigned, ignoring", shardId);
                 final ReplicationResponse response = new ReplicationResponse();
-                response.setShardInfo(new ReplicationResponse.ShardInfo(shardRoutingTable.size(), shardRoutingTable.size()));
+                response.setShardInfo(ReplicationResponse.ShardInfo.allSuccessful(shardRoutingTable.size()));
                 listener.onResponse(response);
                 return;
             }
@@ -786,7 +786,7 @@ private void sendVerifyShardBlockRequest(
             if (shardRoutingTable.primaryShard().unassigned()) {
                 logger.debug("primary shard {} is unassigned, ignoring", shardId);
                 final ReplicationResponse response = new ReplicationResponse();
-                response.setShardInfo(new ReplicationResponse.ShardInfo(shardRoutingTable.size(), shardRoutingTable.size()));
+                response.setShardInfo(ReplicationResponse.ShardInfo.allSuccessful(shardRoutingTable.size()));
                 listener.onResponse(response);
                 return;
             }

server/src/test/java/org/elasticsearch/action/DocWriteResponseTests.java

@@ -85,7 +85,7 @@ public void testToXContentDoesntIncludeForcedRefreshUnlessForced() throws IOExce
         ) {
             // DocWriteResponse is abstract so we have to sneak a subclass in here to test it.
         };
-        response.setShardInfo(new ShardInfo(1, 1));
+        response.setShardInfo(ShardInfo.allSuccessful(1));
         response.setForcedRefresh(false);
         try (XContentBuilder builder = JsonXContent.contentBuilder()) {
             response.toXContent(builder, ToXContent.EMPTY_PARAMS);

server/src/test/java/org/elasticsearch/action/delete/DeleteResponseTests.java

@@ -48,7 +48,7 @@ public void testToXContent() throws IOException {
         {
             DeleteResponse response = new DeleteResponse(new ShardId("index", "index_uuid", 0), "id", -1, 0, 7, true);
             response.setForcedRefresh(true);
-            response.setShardInfo(new ReplicationResponse.ShardInfo(10, 5));
+            response.setShardInfo(ReplicationResponse.ShardInfo.of(10, 5));
             String output = Strings.toString(response);
             assertEquals(XContentHelper.stripWhitespace("""
                 {

server/src/test/java/org/elasticsearch/action/index/IndexRequestTests.java

@@ -134,7 +134,7 @@ public void testIndexResponse() {
         IndexResponse indexResponse = new IndexResponse(shardId, id, SequenceNumbers.UNASSIGNED_SEQ_NO, 0, version, created);
         int total = randomIntBetween(1, 10);
         int successful = randomIntBetween(1, 10);
-        ReplicationResponse.ShardInfo shardInfo = new ReplicationResponse.ShardInfo(total, successful);
+        ReplicationResponse.ShardInfo shardInfo = ReplicationResponse.ShardInfo.of(total, successful);
         indexResponse.setShardInfo(shardInfo);
         boolean forcedRefresh = false;
         if (randomBoolean()) {

server/src/test/java/org/elasticsearch/action/index/IndexResponseTests.java

@@ -51,7 +51,7 @@ public void testToXContent() throws IOException {
         {
             IndexResponse indexResponse = new IndexResponse(new ShardId("index", "index_uuid", 0), "id", -1, 17, 7, true);
             indexResponse.setForcedRefresh(true);
-            indexResponse.setShardInfo(new ReplicationResponse.ShardInfo(10, 5));
+            indexResponse.setShardInfo(ReplicationResponse.ShardInfo.of(10, 5));
             String output = Strings.toString(indexResponse);
             assertEquals(XContentHelper.stripWhitespace("""
                 {

server/src/test/java/org/elasticsearch/action/support/replication/BroadcastReplicationTests.java

@@ -164,7 +164,7 @@ public void testStartedPrimary() throws InterruptedException, ExecutionException
         ActionTestUtils.execute(broadcastReplicationAction, null, new DummyBroadcastRequest(index), response);
         for (Tuple<ShardId, ActionListener<ReplicationResponse>> shardRequests : broadcastReplicationAction.capturedShardRequests) {
             ReplicationResponse replicationResponse = new ReplicationResponse();
-            replicationResponse.setShardInfo(new ReplicationResponse.ShardInfo(1, 1));
+            replicationResponse.setShardInfo(ReplicationResponse.ShardInfo.allSuccessful(1));
             shardRequests.v2().onResponse(replicationResponse);
         }
         logger.info("total shards: {}, ", response.get().getTotalShards());
@@ -198,7 +198,7 @@ public void testResultCombine() throws InterruptedException, ExecutionException,
                     );
                     failed++;
                 }
-                replicationResponse.setShardInfo(new ReplicationResponse.ShardInfo(2, shardsSucceeded, failures));
+                replicationResponse.setShardInfo(ReplicationResponse.ShardInfo.of(2, shardsSucceeded, failures));
                 shardRequests.v2().onResponse(replicationResponse);
             } else {
                 // sometimes fail

server/src/test/java/org/elasticsearch/action/support/replication/ReplicationResponseTests.java

@@ -35,34 +35,35 @@ public class ReplicationResponseTests extends ESTestCase {
     public void testShardInfoToString() {
         final int total = 5;
         final int successful = randomIntBetween(1, total);
-        final ShardInfo shardInfo = new ShardInfo(total, successful);
+        final ShardInfo shardInfo = ShardInfo.of(total, successful);
         assertEquals(Strings.format("ShardInfo{total=5, successful=%d, failures=[]}", successful), shardInfo.toString());
     }
 
     public void testShardInfoToXContent() throws IOException {
         {
-            ShardInfo shardInfo = new ShardInfo(5, 3);
+            ShardInfo shardInfo = ShardInfo.of(5, 3);
             String output = Strings.toString(shardInfo);
             assertEquals("{\"total\":5,\"successful\":3,\"failed\":0}", output);
         }
         {
-            ShardInfo shardInfo = new ShardInfo(
+            ShardInfo shardInfo = ShardInfo.of(
                 6,
                 4,
-                new ShardInfo.Failure(
-                    new ShardId("index", "_uuid", 3),
-                    "_node_id",
-                    new IllegalArgumentException("Wrong"),
-                    RestStatus.BAD_REQUEST,
-                    false
-                ),
-                new ShardInfo.Failure(
-                    new ShardId("index", "_uuid", 1),
-                    "_node_id",
-                    new CircuitBreakingException("Wrong", 12, 21, CircuitBreaker.Durability.PERMANENT),
-                    RestStatus.NOT_ACCEPTABLE,
-                    true
-                )
+                new ShardInfo.Failure[] {
+                    new ShardInfo.Failure(
+                        new ShardId("index", "_uuid", 3),
+                        "_node_id",
+                        new IllegalArgumentException("Wrong"),
+                        RestStatus.BAD_REQUEST,
+                        false
+                    ),
+                    new ShardInfo.Failure(
+                        new ShardId("index", "_uuid", 1),
+                        "_node_id",
+                        new CircuitBreakingException("Wrong", 12, 21, CircuitBreaker.Durability.PERMANENT),
+                        RestStatus.NOT_ACCEPTABLE,
+                        true
+                    ) }
             );
             String output = Strings.toString(shardInfo);
             assertEquals(XContentHelper.stripWhitespace("""

server/src/test/java/org/elasticsearch/action/support/replication/TransportReplicationActionTests.java

@@ -1468,7 +1468,7 @@ static class TestResponse extends ReplicationResponse {
         }
 
         TestResponse() {
-            setShardInfo(new ShardInfo());
+            setShardInfo(ReplicationResponse.ShardInfo.EMPTY);
         }
     }
 

server/src/test/java/org/elasticsearch/action/update/UpdateResponseTests.java

@@ -62,7 +62,7 @@ public void testToXContent() throws IOException {
         }
         {
             UpdateResponse updateResponse = new UpdateResponse(
-                new ReplicationResponse.ShardInfo(10, 6),
+                ReplicationResponse.ShardInfo.of(10, 6),
                 new ShardId("index", "index_uuid", 1),
                 "id",
                 3,
@@ -94,7 +94,7 @@ public void testToXContent() throws IOException {
             fields.put("isbn", new DocumentField("isbn", Collections.singletonList("ABC-123")));
 
             UpdateResponse updateResponse = new UpdateResponse(
-                new ReplicationResponse.ShardInfo(3, 2),
+                ReplicationResponse.ShardInfo.of(3, 2),
                 new ShardId("books", "books_uuid", 2),
                 "1",
                 7,

test/framework/src/main/java/org/elasticsearch/test/RandomObjects.java

@@ -246,7 +246,7 @@ public static Tuple<ShardInfo, ShardInfo> randomShardInfo(Random random) {
     public static Tuple<ShardInfo, ShardInfo> randomShardInfo(Random random, boolean withShardFailures) {
         int total = randomIntBetween(random, 1, 10);
         if (withShardFailures == false) {
-            return Tuple.tuple(new ShardInfo(total, total), new ShardInfo(total, total));
+            return Tuple.tuple(ShardInfo.allSuccessful(total), ShardInfo.allSuccessful(total));
         }
 
         int successful = randomIntBetween(random, 1, Math.max(1, (total - 1)));
@@ -260,7 +260,7 @@ public static Tuple<ShardInfo, ShardInfo> randomShardInfo(Random random, boolean
             actualFailures[i] = failure.v1();
             expectedFailures[i] = failure.v2();
         }
-        return Tuple.tuple(new ShardInfo(total, successful, actualFailures), new ShardInfo(total, successful, expectedFailures));
+        return Tuple.tuple(ShardInfo.of(total, successful, actualFailures), ShardInfo.of(total, successful, expectedFailures));
     }
 
     /**