Add HTTP request info to leaking buffers (#116130) (#117515)

Author: mhl-b

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpServerTransport.java

@@ -33,6 +33,7 @@
 import io.netty.handler.timeout.ReadTimeoutException;
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import io.netty.util.AttributeKey;
+import io.netty.util.ResourceLeakDetector;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -410,6 +411,9 @@ protected Result beginEncode(HttpResponse httpResponse, String acceptEncoding) t
                     }
                 });
             }
+            if (ResourceLeakDetector.isEnabled()) {
+                ch.pipeline().addLast(new Netty4LeakDetectionHandler());
+            }
             ch.pipeline()
                 .addLast(
                     "pipelining",

modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4LeakDetectionHandler.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.http.netty4;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+import io.netty.handler.codec.http.HttpContent;
+import io.netty.handler.codec.http.HttpRequest;
+
+import org.elasticsearch.tasks.Task;
+
+/**
+ * Inbound channel handler that enrich leaking buffers information from HTTP request.
+ * It helps to detect which handler is leaking buffers. Especially integration tests that run with
+ * paranoid leak detector that samples all buffers for leaking. Supplying informative opaque-id in
+ * integ test helps to narrow down problem (for example test name).
+ */
+public class Netty4LeakDetectionHandler extends ChannelInboundHandlerAdapter {
+
+    private String info;
+
+    @Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) {
+        if (msg instanceof HttpRequest request) {
+            var opaqueId = request.headers().get(Task.X_OPAQUE_ID_HTTP_HEADER);
+            info = "method: " + request.method() + "; uri: " + request.uri() + "; x-opaque-id: " + opaqueId;
+        }
+        if (msg instanceof HttpContent content) {
+            content.touch(info);
+        }
+        ctx.fireChannelRead(msg);
+    }
+}