Optimising node to node communication by serializing node attribute in DiscoveryNode only in scenarioes where it is required

libs/core/src/main/java/org/opensearch/core/common/io/stream/StreamOutput.java

@@ -969,9 +969,13 @@ public <T extends Writeable> void writeOptionalArray(@Nullable T[] array) throws
     }
 
     public void writeOptionalWriteable(@Nullable Writeable writeable) throws IOException {
+        writeOptionalWriteable((out, writable) -> writable.writeTo(out), writeable);
+    }
+
+    public <T extends Writeable> void writeOptionalWriteable(final Writer<T> writer, @Nullable T writeable) throws IOException {
         if (writeable != null) {
             writeBoolean(true);
-            writeable.writeTo(this);
+            writer.write(this, writeable);
         } else {
             writeBoolean(false);
         }

server/src/main/java/org/opensearch/action/admin/cluster/allocation/ClusterAllocationExplanation.java

@@ -95,7 +95,7 @@ public ClusterAllocationExplanation(StreamInput in) throws IOException {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         shardRouting.writeTo(out);
-        out.writeOptionalWriteable(currentNode);
+        out.writeOptionalWriteable((stream, node) -> node.writeToWithAttribute(stream), currentNode);
         out.writeOptionalWriteable(relocationTargetNode);
         out.writeOptionalWriteable(clusterInfo);
         shardAllocationDecision.writeTo(out);

server/src/main/java/org/opensearch/action/support/nodes/BaseNodeResponse.java

@@ -67,6 +67,6 @@ public DiscoveryNode getNode() {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        node.writeTo(out);
+        node.writeToWithAttribute(out);
     }
 }

server/src/main/java/org/opensearch/cluster/ClusterState.java

@@ -781,7 +781,7 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeString(stateUUID);
         metadata.writeTo(out);
         routingTable.writeTo(out);
-        nodes.writeTo(out);
+        nodes.writeToWithAttribute(out);
         blocks.writeTo(out);
         // filter out custom states not supported by the other node
         int numberOfCustoms = 0;
@@ -859,13 +859,23 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeString(toUuid);
             out.writeLong(toVersion);
             routingTable.writeTo(out);
-            nodes.writeTo(out);
+            nodesWriteToWithAttributes(nodes, out);
             metadata.writeTo(out);
             blocks.writeTo(out);
             customs.writeTo(out);
             out.writeVInt(minimumClusterManagerNodesOnPublishingClusterManager);
         }
 
+        private void nodesWriteToWithAttributes(Diff<DiscoveryNodes> nodes, StreamOutput out) throws IOException {
+            DiscoveryNodes part = nodes.apply(null);
+            if (part != null) {
+                out.writeBoolean(true);
+                part.writeToWithAttribute(out);
+            } else {
+                out.writeBoolean(false);
+            }
+        }
+
         @Override
         public ClusterState apply(ClusterState state) {
             Builder builder = new Builder(clusterName);

server/src/main/java/org/opensearch/cluster/coordination/Join.java

@@ -78,8 +78,8 @@ public Join(StreamInput in) throws IOException {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        sourceNode.writeTo(out);
-        targetNode.writeTo(out);
+        sourceNode.writeToWithAttribute(out);
+        targetNode.writeToWithAttribute(out);
         out.writeLong(term);
         out.writeLong(lastAcceptedTerm);
         out.writeLong(lastAcceptedVersion);

server/src/main/java/org/opensearch/cluster/coordination/JoinRequest.java

@@ -89,7 +89,7 @@ public JoinRequest(StreamInput in) throws IOException {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
-        sourceNode.writeTo(out);
+        sourceNode.writeToWithAttribute(out);
         if (out.getVersion().onOrAfter(LegacyESVersion.V_7_7_0)) {
             out.writeLong(minimumTerm);
         }

server/src/main/java/org/opensearch/cluster/coordination/StartJoinRequest.java

@@ -64,7 +64,7 @@ public StartJoinRequest(StreamInput input) throws IOException {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
-        sourceNode.writeTo(out);
+        sourceNode.writeToWithAttribute(out);
         out.writeLong(term);
     }
 

server/src/main/java/org/opensearch/cluster/node/DiscoveryNode.java

@@ -385,17 +385,34 @@ public DiscoveryNode(StreamInput in) throws IOException {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
+        if (out.getVersion().onOrAfter(Version.V_2_17_0)) {
+            writeToUtil(out, false);
+        } else {
+            writeToUtil(out, true);
+        }
+    }
+
+    public void writeToWithAttribute(StreamOutput out) throws IOException {
+        writeToUtil(out, true);
+    }
+
+    public void writeToUtil(StreamOutput out, boolean includeAllAttributes) throws IOException {
         out.writeString(nodeName);
         out.writeString(nodeId);
         out.writeString(ephemeralId);
         out.writeString(hostName);
         out.writeString(hostAddress);
         address.writeTo(out);
-        out.writeVInt(attributes.size());
-        for (Map.Entry<String, String> entry : attributes.entrySet()) {
-            out.writeString(entry.getKey());
-            out.writeString(entry.getValue());
+        if (includeAllAttributes) {
+            out.writeVInt(attributes.size());
+            for (Map.Entry<String, String> entry : attributes.entrySet()) {
+                out.writeString(entry.getKey());
+                out.writeString(entry.getValue());
+            }
+        } else {
+            out.writeVInt(0);
         }
+
         if (out.getVersion().onOrAfter(LegacyESVersion.V_7_3_0)) {
             out.writeVInt(roles.size());
             for (final DiscoveryNodeRole role : roles) {

server/src/main/java/org/opensearch/cluster/node/DiscoveryNodes.java

@@ -701,6 +701,14 @@ public String shortSummary() {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
+        writeToUtil((output, value) -> value.writeTo(output), out);
+    }
+
+    public void writeToWithAttribute(StreamOutput out) throws IOException {
+        writeToUtil((output, value) -> value.writeToWithAttribute(output), out);
+    }
+
+    private void writeToUtil(final Writer<DiscoveryNode> writer, StreamOutput out) throws IOException {
         if (clusterManagerNodeId == null) {
             out.writeBoolean(false);
         } else {
@@ -709,7 +717,7 @@ public void writeTo(StreamOutput out) throws IOException {
         }
         out.writeVInt(nodes.size());
         for (DiscoveryNode node : this) {
-            node.writeTo(out);
+            writer.write(out, node);
         }
     }
 

server/src/main/java/org/opensearch/cluster/routing/allocation/AbstractAllocationDecision.java

@@ -107,7 +107,7 @@ public List<NodeAllocationResult> getNodeDecisions() {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        out.writeOptionalWriteable(targetNode);
+        out.writeOptionalWriteable((stream, node) -> node.writeToWithAttribute(stream), targetNode);
         if (nodeDecisions != null) {
             out.writeBoolean(true);
             out.writeList(nodeDecisions);

server/src/main/java/org/opensearch/cluster/routing/allocation/NodeAllocationResult.java

@@ -104,7 +104,7 @@ public NodeAllocationResult(StreamInput in) throws IOException {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        node.writeTo(out);
+        node.writeToWithAttribute(out);
         out.writeOptionalWriteable(shardStoreInfo);
         out.writeOptionalWriteable(canAllocateDecision);
         nodeDecision.writeTo(out);

server/src/main/java/org/opensearch/gateway/remote/model/RemoteDiscoveryNodes.java

@@ -88,7 +88,12 @@ public UploadedMetadata getUploadedMetadata() {
 
     @Override
     public InputStream serialize() throws IOException {
-        return DISCOVERY_NODES_FORMAT.serialize(discoveryNodes, generateBlobFileName(), getCompressor()).streamInput();
+        return DISCOVERY_NODES_FORMAT.serialize(
+            (out, discoveryNode) -> discoveryNode.writeToWithAttribute(out),
+            discoveryNodes,
+            generateBlobFileName(),
+            getCompressor()
+        ).streamInput();
     }
 
     @Override

server/src/main/java/org/opensearch/indices/recovery/PeerRecoveryTargetService.java

@@ -295,6 +295,7 @@ private void doRecovery(final long recoveryId, final StartRecoveryRequest preExi
                 logger.debug("{} reestablishing recovery from {}", startRequest.shardId(), startRequest.sourceNode());
             }
         }
+
         transportService.sendRequest(
             startRequest.sourceNode(),
             actionName,

server/src/main/java/org/opensearch/indices/recovery/StartRecoveryRequest.java

@@ -144,8 +144,8 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeLong(recoveryId);
         shardId.writeTo(out);
         out.writeString(targetAllocationId);
-        sourceNode.writeTo(out);
-        targetNode.writeTo(out);
+        sourceNode.writeToWithAttribute(out);
+        targetNode.writeToWithAttribute(out);
         metadataSnapshot.writeTo(out);
         out.writeBoolean(primaryRelocation);
         out.writeLong(startingSeqNo);

server/src/main/java/org/opensearch/repositories/blobstore/ChecksumWritableBlobStoreFormat.java

@@ -28,6 +28,7 @@
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.core.common.io.stream.Writeable;
+import org.opensearch.core.common.io.stream.Writeable.Writer;
 import org.opensearch.core.compress.Compressor;
 import org.opensearch.core.compress.CompressorRegistry;
 import org.opensearch.gateway.CorruptStateException;
@@ -56,6 +57,10 @@ public ChecksumWritableBlobStoreFormat(String codec, CheckedFunction<StreamInput
     }
 
     public BytesReference serialize(final T obj, final String blobName, final Compressor compressor) throws IOException {
+        return serialize((out, unSerializedObj) -> unSerializedObj.writeTo(out), obj, blobName, compressor);
+    }
+
+    public BytesReference serialize(final Writer<T> writer, T obj, final String blobName, final Compressor compressor) throws IOException {
         try (BytesStreamOutput outputStream = new BytesStreamOutput()) {
             try (
                 OutputStreamIndexOutput indexOutput = new OutputStreamIndexOutput(
@@ -76,7 +81,7 @@ public void close() throws IOException {
                 }; StreamOutput stream = new OutputStreamStreamOutput(compressor.threadLocalOutputStream(indexOutputOutputStream));) {
                     // TODO The stream version should be configurable
                     stream.setVersion(Version.CURRENT);
-                    obj.writeTo(stream);
+                    writer.write(stream, obj);
                 }
                 CodecUtil.writeFooter(indexOutput);
             }

server/src/main/java/org/opensearch/transport/TransportService.java

@@ -759,7 +759,7 @@ public HandshakeResponse(StreamInput in) throws IOException {
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            out.writeOptionalWriteable(discoveryNode);
+            out.writeOptionalWriteable((stream, node) -> node.writeToWithAttribute(stream), discoveryNode);
             clusterName.writeTo(out);
             if (out.getVersion().before(Version.V_1_0_0)) {
                 out.writeVersion(LegacyESVersion.V_7_10_2);

server/src/test/java/org/opensearch/gateway/remote/RemoteClusterStateAttributesManagerTests.java

@@ -140,7 +140,12 @@ public void testGetAsyncReadRunnable_DiscoveryNodes() throws IOException, Interr
         DiscoveryNodes discoveryNodes = getDiscoveryNodes();
         String fileName = randomAlphaOfLength(10);
         when(blobStoreTransferService.downloadBlob(anyIterable(), anyString())).thenReturn(
-            DISCOVERY_NODES_FORMAT.serialize(discoveryNodes, fileName, compressor).streamInput()
+            DISCOVERY_NODES_FORMAT.serialize(
+                (out, discoveryNode) -> discoveryNode.writeToWithAttribute(out),
+                discoveryNodes,
+                fileName,
+                compressor
+            ).streamInput()
         );
         RemoteDiscoveryNodes remoteObjForDownload = new RemoteDiscoveryNodes(fileName, "cluster-uuid", compressor);
         CountDownLatch latch = new CountDownLatch(1);

server/src/test/java/org/opensearch/gateway/remote/RemoteClusterStateServiceTests.java

@@ -1186,7 +1186,12 @@ public void testGetClusterStateUsingDiff() throws IOException {
             diffManifestBuilder.discoveryNodesUpdated(true);
             manifestBuilder.discoveryNodesMetadata(new UploadedMetadataAttribute(DISCOVERY_NODES, DISCOVERY_NODES_FILENAME));
             when(blobContainer.readBlob(DISCOVERY_NODES_FILENAME)).thenAnswer(invocationOnMock -> {
-                BytesReference bytes = DISCOVERY_NODES_FORMAT.serialize(nodesBuilder.build(), DISCOVERY_NODES_FILENAME, compressor);
+                BytesReference bytes = DISCOVERY_NODES_FORMAT.serialize(
+                    (out, nodes) -> nodes.writeToWithAttribute(out),
+                    nodesBuilder.build(),
+                    DISCOVERY_NODES_FILENAME,
+                    compressor
+                );
                 return new ByteArrayInputStream(bytes.streamInput().readAllBytes());
             });
         }

server/src/test/java/org/opensearch/gateway/remote/model/RemoteDiscoveryNodesTests.java

@@ -143,7 +143,7 @@ public void testSerDe() throws IOException {
     public void testExceptionDuringSerialization() throws IOException {
         DiscoveryNodes nodes = mock(DiscoveryNodes.class);
         RemoteDiscoveryNodes remoteObjectForUpload = new RemoteDiscoveryNodes(nodes, METADATA_VERSION, clusterUUID, compressor);
-        doThrow(new IOException("mock-exception")).when(nodes).writeTo(any());
+        doThrow(new IOException("mock-exception")).when(nodes).writeToWithAttribute(any());
         IOException iea = assertThrows(IOException.class, remoteObjectForUpload::serialize);
     }
 

server/src/test/java/org/opensearch/repositories/blobstore/ChecksumWritableBlobStoreFormatTests.java

@@ -35,14 +35,20 @@ public class ChecksumWritableBlobStoreFormatTests extends OpenSearchTestCase {
 
     public void testSerDe() throws IOException {
         IndexMetadata indexMetadata = getIndexMetadata();
-        BytesReference bytesReference = clusterBlocksFormat.serialize(indexMetadata, TEST_BLOB_FILE_NAME, CompressorRegistry.none());
+        BytesReference bytesReference = clusterBlocksFormat.serialize(
+            (out, metadata) -> metadata.writeTo(out),
+            indexMetadata,
+            TEST_BLOB_FILE_NAME,
+            CompressorRegistry.none()
+        );
         IndexMetadata readIndexMetadata = clusterBlocksFormat.deserialize(TEST_BLOB_FILE_NAME, bytesReference);
         assertThat(readIndexMetadata, is(indexMetadata));
     }
 
     public void testSerDeForCompressed() throws IOException {
         IndexMetadata indexMetadata = getIndexMetadata();
         BytesReference bytesReference = clusterBlocksFormat.serialize(
+            (out, metadata) -> metadata.writeTo(out),
             indexMetadata,
             TEST_BLOB_FILE_NAME,
             CompressorRegistry.getCompressor(DeflateCompressor.NAME)