From d654c9be49d2cc5a16bbd45393af2b2eda01ad92 Mon Sep 17 00:00:00 2001
From: Ryan Ernst <ryan@iernst.net>
Date: Sun, 6 Apr 2025 06:30:42 -0700
Subject: [PATCH] Convert TransportMessage to an interface

TransportMessage is unnecessarily an abstract class, which is more rigid
when trying to refactor due to only being able to extend a single class.
This commit makes TransportMessage an interface with default methods.
---
 .../elasticsearch/transport/TransportMessage.java | 15 +++++----------
 .../elasticsearch/transport/TransportRequest.java |  2 +-
 .../transport/TransportResponse.java              |  2 +-
 3 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/transport/TransportMessage.java b/server/src/main/java/org/elasticsearch/transport/TransportMessage.java
index b93cdd4cbcbae..555d5e1c24b4e 100644
--- a/server/src/main/java/org/elasticsearch/transport/TransportMessage.java
+++ b/server/src/main/java/org/elasticsearch/transport/TransportMessage.java
@@ -12,20 +12,15 @@
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.core.RefCounted;
 
-public abstract class TransportMessage implements Writeable, RefCounted {
-
-    /**
-     * Constructs a new empty transport message
-     */
-    public TransportMessage() {}
+public interface TransportMessage extends Writeable, RefCounted {
 
     @Override
-    public void incRef() {
+    default void incRef() {
         // noop, override to manage the life-cycle of resources held by a transport message
     }
 
     @Override
-    public boolean tryIncRef() {
+    default boolean tryIncRef() {
         // noop, override to manage the life-cycle of resources held by a transport message
         return true;
     }
@@ -38,13 +33,13 @@ public boolean tryIncRef() {
      * layer in a manner that might end up nesting too deeply. When in doubt, dispatch any further work onto a separate thread.
      */
     @Override
-    public boolean decRef() {
+    default boolean decRef() {
         // noop, override to manage the life-cycle of resources held by a transport message
         return false;
     }
 
     @Override
-    public boolean hasReferences() {
+    default boolean hasReferences() {
         // noop, override to manage the life-cycle of resources held by a transport message
         return true;
     }
diff --git a/server/src/main/java/org/elasticsearch/transport/TransportRequest.java b/server/src/main/java/org/elasticsearch/transport/TransportRequest.java
index 393d015123473..e714ae6310dcf 100644
--- a/server/src/main/java/org/elasticsearch/transport/TransportRequest.java
+++ b/server/src/main/java/org/elasticsearch/transport/TransportRequest.java
@@ -18,7 +18,7 @@
 import java.io.IOException;
 import java.net.InetSocketAddress;
 
-public abstract class TransportRequest extends TransportMessage implements TaskAwareRequest {
+public abstract class TransportRequest implements TransportMessage, TaskAwareRequest {
 
     @Nullable // set by the transport service on inbound messages; unset on outbound messages
     private InetSocketAddress remoteAddress;
diff --git a/server/src/main/java/org/elasticsearch/transport/TransportResponse.java b/server/src/main/java/org/elasticsearch/transport/TransportResponse.java
index e259d2abda119..16ee5160c58d8 100644
--- a/server/src/main/java/org/elasticsearch/transport/TransportResponse.java
+++ b/server/src/main/java/org/elasticsearch/transport/TransportResponse.java
@@ -13,7 +13,7 @@
 
 import java.io.IOException;
 
-public abstract class TransportResponse extends TransportMessage {
+public abstract class TransportResponse implements TransportMessage {
 
     /**
      * Constructs a new empty transport response