fix triple graceful shutdown

dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/DubboShutdownHook.java

@@ -22,6 +22,7 @@
 import org.apache.dubbo.common.logger.ErrorTypeAwareLogger;
 import org.apache.dubbo.common.logger.LoggerFactory;
 import org.apache.dubbo.common.utils.Assert;
+import org.apache.dubbo.remoting.exchange.PortUnificationExchanger;
 import org.apache.dubbo.rpc.GracefulShutdown;
 import org.apache.dubbo.rpc.model.ApplicationModel;
 import org.apache.dubbo.rpc.model.ModuleModel;
@@ -93,6 +94,8 @@ private void doDestroy() {
         for (GracefulShutdown gracefulShutdown : gracefulShutdowns) {
             gracefulShutdown.readonly();
         }
+        // close all exchangers to reject new requests
+        PortUnificationExchanger.goaway();
 
         boolean hasModuleBindSpring = false;
         // check if any modules are bound to Spring

dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/api/GoAwayEvent.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.remoting.api;
+
+/**
+ * Event used to trigger graceful shutdown for protocols that support it.
+ * For HTTP/2 (Triple protocol), this event triggers sending a GOAWAY frame
+ * to notify clients that the server is shutting down.
+ *
+ * <p>This event is fired through Netty's user event mechanism and is handled
+ * by protocol-specific handlers (e.g., TripleServerConnectionHandler for Triple protocol).
+ * Protocols that don't support GOAWAY (e.g., Dubbo protocol) will simply ignore this event.
+ */
+public class GoAwayEvent {
+
+    /**
+     * Singleton instance of GoAwayEvent.
+     */
+    public static final GoAwayEvent INSTANCE = new GoAwayEvent();
+
+    private GoAwayEvent() {
+        // Private constructor to enforce singleton pattern
+    }
+}

dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/api/pu/AbstractPortUnificationServer.java

@@ -103,4 +103,6 @@ public Map<String, ChannelHandler> getSupportedHandlers() {
         // this getter is just used by implementation of this class
         return supportedHandlers;
     }
+
+    public abstract void goaway();
 }

dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/exchange/PortUnificationExchanger.java

@@ -37,7 +37,8 @@ public class PortUnificationExchanger {
 
     private static final ErrorTypeAwareLogger log =
             LoggerFactory.getErrorTypeAwareLogger(PortUnificationExchanger.class);
-    private static final ConcurrentMap<String, RemotingServer> servers = new ConcurrentHashMap<>();
+
+    private static final ConcurrentMap<String, AbstractPortUnificationServer> servers = new ConcurrentHashMap<>();
 
     public static RemotingServer bind(URL url, ChannelHandler handler) {
         ConcurrentHashMapUtils.computeIfAbsent(servers, url.getAddress(), addr -> {
@@ -52,7 +53,7 @@ public static RemotingServer bind(URL url, ChannelHandler handler) {
         });
 
         servers.computeIfPresent(url.getAddress(), (addr, server) -> {
-            ((AbstractPortUnificationServer) server).addSupportedProtocol(url, handler);
+            server.addSupportedProtocol(url, handler);
             return server;
         });
         return servers.get(url.getAddress());
@@ -69,9 +70,9 @@ public static AbstractConnectionClient connect(URL url, ChannelHandler handler)
     }
 
     public static void close() {
-        final ArrayList<RemotingServer> toClose = new ArrayList<>(servers.values());
+        final ArrayList<AbstractPortUnificationServer> toClose = new ArrayList<>(servers.values());
         servers.clear();
-        for (RemotingServer server : toClose) {
+        for (AbstractPortUnificationServer server : toClose) {
             try {
                 server.close();
             } catch (Throwable throwable) {
@@ -80,8 +81,18 @@ public static void close() {
         }
     }
 
+    public static void goaway() {
+        for (AbstractPortUnificationServer server : servers.values()) {
+            try {
+                server.goaway();
+            } catch (Throwable throwable) {
+                log.error(PROTOCOL_ERROR_CLOSE_SERVER, "", "", "Goaway all port unification server failed", throwable);
+            }
+        }
+    }
+
     // for test
-    public static ConcurrentMap<String, RemotingServer> getServers() {
+    public static ConcurrentMap<String, AbstractPortUnificationServer> getServers() {
         return servers;
     }
 

dubbo-remoting/dubbo-remoting-netty/src/main/java/org/apache/dubbo/remoting/transport/netty/NettyPortUnificationServer.java

@@ -71,6 +71,16 @@ public void addSupportedProtocol(URL url, ChannelHandler handler) {
         super.addSupportedProtocol(url, ChannelHandlers.wrap(handler, url));
     }
 
+    @Override
+    public void goaway() {
+        // Netty 3 does not support HTTP/2 (Triple protocol), so we only need to mark channels as closing.
+        // The actual graceful shutdown for Dubbo protocol is handled by sending READONLY_EVENT
+        // through DubboGracefulShutdown.readonly() before this method is called.
+        for (Channel channel : getChannels()) {
+            channel.startClose();
+        }
+    }
+
     @Override
     public void close() {
         if (channel != null) {

dubbo-remoting/dubbo-remoting-netty4/src/main/java/org/apache/dubbo/remoting/transport/netty4/NettyPortUnificationServer.java

@@ -24,6 +24,7 @@
 import org.apache.dubbo.remoting.ChannelHandler;
 import org.apache.dubbo.remoting.Constants;
 import org.apache.dubbo.remoting.RemotingException;
+import org.apache.dubbo.remoting.api.GoAwayEvent;
 import org.apache.dubbo.remoting.api.WireProtocol;
 import org.apache.dubbo.remoting.api.pu.AbstractPortUnificationServer;
 import org.apache.dubbo.remoting.transport.dispatcher.ChannelHandlers;
@@ -87,6 +88,20 @@ public void close() {
         }
     }
 
+    @Override
+    public void goaway() {
+        for (Channel channel : getChannels()) {
+            channel.startClose();
+            // Fire GoAwayEvent through Netty pipeline to trigger protocol-specific graceful shutdown
+            // For HTTP/2 (Triple protocol), TripleServerConnectionHandler will handle this event
+            // and send Http2GoAwayFrame to notify clients
+            // For other protocols (e.g., Dubbo), this event will be ignored
+            if (channel instanceof NettyChannel) {
+                ((NettyChannel) channel).getNioChannel().pipeline().fireUserEventTriggered(GoAwayEvent.INSTANCE);
+            }
+        }
+    }
+
     public void bind() throws Throwable {
         if (channel == null) {
             doOpen();

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/protocol/AbstractProxyProtocol.java

@@ -16,14 +16,10 @@
  */
 package org.apache.dubbo.rpc.protocol;
 
-import org.apache.dubbo.common.Parameters;
 import org.apache.dubbo.common.URL;
 import org.apache.dubbo.common.utils.NetUtils;
 import org.apache.dubbo.common.utils.StringUtils;
-import org.apache.dubbo.remoting.Channel;
-import org.apache.dubbo.remoting.ChannelHandler;
 import org.apache.dubbo.remoting.Constants;
-import org.apache.dubbo.remoting.RemotingException;
 import org.apache.dubbo.remoting.RemotingServer;
 import org.apache.dubbo.rpc.Exporter;
 import org.apache.dubbo.rpc.Invocation;
@@ -33,8 +29,6 @@
 import org.apache.dubbo.rpc.Result;
 import org.apache.dubbo.rpc.RpcException;
 
-import java.net.InetSocketAddress;
-import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -211,68 +205,4 @@ public Map<String, Object> getAttributes() {
             return attributes;
         }
     }
-
-    protected abstract class RemotingServerAdapter implements RemotingServer {
-
-        public abstract Object getDelegateServer();
-
-        /**
-         * @return
-         */
-        @Override
-        public boolean isBound() {
-            return false;
-        }
-
-        @Override
-        public Collection<Channel> getChannels() {
-            return null;
-        }
-
-        @Override
-        public Channel getChannel(InetSocketAddress remoteAddress) {
-            return null;
-        }
-
-        @Override
-        public void reset(Parameters parameters) {}
-
-        @Override
-        public void reset(URL url) {}
-
-        @Override
-        public URL getUrl() {
-            return null;
-        }
-
-        @Override
-        public ChannelHandler getChannelHandler() {
-            return null;
-        }
-
-        @Override
-        public InetSocketAddress getLocalAddress() {
-            return null;
-        }
-
-        @Override
-        public void send(Object message) throws RemotingException {}
-
-        @Override
-        public void send(Object message, boolean sent) throws RemotingException {}
-
-        @Override
-        public void close() {}
-
-        @Override
-        public void close(int timeout) {}
-
-        @Override
-        public void startClose() {}
-
-        @Override
-        public boolean isClosed() {
-            return false;
-        }
-    }
 }

dubbo-rpc/dubbo-rpc-triple/src/main/java/org/apache/dubbo/rpc/protocol/tri/transport/TripleServerConnectionHandler.java

@@ -18,6 +18,7 @@
 
 import org.apache.dubbo.common.logger.ErrorTypeAwareLogger;
 import org.apache.dubbo.common.logger.LoggerFactory;
+import org.apache.dubbo.remoting.api.GoAwayEvent;
 
 import java.io.IOException;
 import java.net.SocketException;
@@ -97,7 +98,13 @@ private boolean isQuiteException(Throwable t) {
 
     @Override
     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
-        super.userEventTriggered(ctx, evt);
+        if (evt instanceof GoAwayEvent) {
+            // Handle GoAwayEvent by initiating graceful shutdown
+            // This will send HTTP/2 GOAWAY frame to notify clients
+            close(ctx, ctx.newPromise());
+        } else {
+            super.userEventTriggered(ctx, evt);
+        }
     }
 
     @Override