[fix]: Gating ser/de of streamAddress in DiscoveryNodes via FeatureFlag

Author: Pranshu-S

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

@@ -37,6 +37,7 @@
 import org.opensearch.common.annotation.PublicApi;
 import org.opensearch.common.settings.Setting;
 import org.opensearch.common.settings.Settings;
+import org.opensearch.common.util.FeatureFlags;
 import org.opensearch.core.common.io.stream.BufferedChecksumStreamOutput;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
@@ -352,7 +353,7 @@ public DiscoveryNode(StreamInput in) throws IOException {
         this.hostName = in.readString().intern();
         this.hostAddress = in.readString().intern();
         this.address = new TransportAddress(in);
-        if (in.getVersion().onOrAfter(Version.V_3_2_0)) {
+        if (in.getVersion().onOrAfter(Version.V_3_2_0) && FeatureFlags.isTransportStreamFeatureEnabled()) {
             this.streamAddress = in.readOptionalWriteable(TransportAddress::new);
         } else {
             streamAddress = null;
@@ -435,7 +436,7 @@ private void writeNodeDetails(StreamOutput out) throws IOException {
         out.writeString(hostName);
         out.writeString(hostAddress);
         address.writeTo(out);
-        if (out.getVersion().onOrAfter(Version.V_3_2_0)) {
+        if (out.getVersion().onOrAfter(Version.V_3_2_0) && FeatureFlags.isTransportStreamFeatureEnabled()) {
             out.writeOptionalWriteable(streamAddress);
         }
     }

server/src/main/java/org/opensearch/common/util/FeatureFlags.java

@@ -117,6 +117,10 @@ public class FeatureFlags {
     public static final String STREAM_TRANSPORT = FEATURE_FLAG_PREFIX + "transport.stream.enabled";
     public static final Setting<Boolean> STREAM_TRANSPORT_SETTING = Setting.boolSetting(STREAM_TRANSPORT, false, Property.NodeScope);
 
+    public static boolean isTransportStreamFeatureEnabled(){
+        return FeatureFlags.isEnabled(FeatureFlags.STREAM_TRANSPORT);
+    }
+
     public static final String ARROW_STREAMS = FEATURE_FLAG_PREFIX + "arrow.streams.enabled";
     public static final Setting<Boolean> ARROW_STREAMS_SETTING = Setting.boolSetting(ARROW_STREAMS, false, Property.NodeScope);