Fix application state router isolation across service chains

dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/router/condition/config/AppStateRouterFactory.java

@@ -18,35 +18,19 @@
 
 import org.apache.dubbo.common.URL;
 import org.apache.dubbo.common.extension.Activate;
+import org.apache.dubbo.rpc.cluster.router.state.CacheableStateRouterFactory;
 import org.apache.dubbo.rpc.cluster.router.state.StateRouter;
-import org.apache.dubbo.rpc.cluster.router.state.StateRouterFactory;
 
 /**
  * Application level router factory
  * AppRouter should after ServiceRouter
  */
 @Activate(order = 150)
-public class AppStateRouterFactory implements StateRouterFactory {
+public class AppStateRouterFactory extends CacheableStateRouterFactory {
     public static final String NAME = "app";
 
-    @SuppressWarnings("rawtypes")
-    private volatile StateRouter router;
-
-    @SuppressWarnings("unchecked")
     @Override
-    public <T> StateRouter<T> getRouter(Class<T> interfaceClass, URL url) {
-        if (router != null) {
-            return router;
-        }
-        synchronized (this) {
-            if (router == null) {
-                router = createRouter(url);
-            }
-        }
-        return router;
-    }
-
-    private <T> StateRouter<T> createRouter(URL url) {
+    protected <T> StateRouter<T> createRouter(Class<T> interfaceClass, URL url) {
         return new AppStateRouter<>(url);
     }
 }

dubbo-cluster/src/test/java/org/apache/dubbo/rpc/cluster/router/condition/config/AppStateRouterFactoryTest.java

@@ -0,0 +1,146 @@
+/*
+ * 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.rpc.cluster.router.condition.config;
+
+import org.apache.dubbo.common.URL;
+import org.apache.dubbo.common.utils.Holder;
+import org.apache.dubbo.rpc.Invocation;
+import org.apache.dubbo.rpc.Invoker;
+import org.apache.dubbo.rpc.RpcInvocation;
+import org.apache.dubbo.rpc.cluster.SingleRouterChain;
+import org.apache.dubbo.rpc.cluster.router.MockInvoker;
+import org.apache.dubbo.rpc.cluster.router.RouterSnapshotNode;
+import org.apache.dubbo.rpc.cluster.router.state.AbstractStateRouter;
+import org.apache.dubbo.rpc.cluster.router.state.BitList;
+import org.apache.dubbo.rpc.cluster.router.state.StateRouter;
+import org.apache.dubbo.rpc.model.ApplicationModel;
+import org.apache.dubbo.rpc.model.ModuleModel;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Verifies that building another service's route chain does not change the first service's routing result.
+ *
+ * @date 2026-10-26
+ */
+class AppStateRouterFactoryTest {
+
+    @Test
+    void orderChainKeepsItsRouteAfterUserChainIsBuilt() {
+        assertFirstServiceChainKeepsItsRoute("OrderService", "UserService");
+    }
+
+    @Test
+    void userChainKeepsItsRouteAfterOrderChainIsBuilt() {
+        assertFirstServiceChainKeepsItsRoute("UserService", "OrderService");
+    }
+
+    private void assertFirstServiceChainKeepsItsRoute(String firstService, String secondService) {
+        ModuleModel moduleModel = ApplicationModel.defaultModel().getDefaultModule();
+        URL firstUrl = consumerUrl(firstService, moduleModel);
+        URL secondUrl = consumerUrl(secondService, moduleModel);
+        AppStateRouterFactory factory = new AppStateRouterFactory();
+
+        // The first service has a downstream filtering router, as it would for a script rule.
+        SingleRouterChain<String> firstChain =
+                chain(factory.getRouter(String.class, firstUrl), new PortFilterRouter(firstUrl, 23982));
+        Invoker<String> firstV1 = invoker(firstService, 23981, moduleModel);
+        Invoker<String> firstV2 = invoker(firstService, 23982, moduleModel);
+        BitList<Invoker<String>> firstInvokers = new BitList<>(Arrays.asList(firstV1, firstV2));
+        firstChain.setInvokers(firstInvokers);
+        assertEquals(
+                Collections.singletonList(firstV2),
+                firstChain.simpleRoute(firstUrl, firstInvokers, new RpcInvocation()));
+
+        // Building a second service chain must not replace the first chain's successor.
+        SingleRouterChain<String> secondChain =
+                chain(factory.getRouter(String.class, secondUrl), new PassThroughRouter(secondUrl));
+        Invoker<String> secondInvoker = invoker(secondService, 23983, moduleModel);
+        BitList<Invoker<String>> secondInvokers = new BitList<>(Collections.singletonList(secondInvoker));
+        secondChain.setInvokers(secondInvokers);
+        assertEquals(
+                Collections.singletonList(secondInvoker),
+                secondChain.simpleRoute(secondUrl, secondInvokers, new RpcInvocation()));
+        assertEquals(
+                Collections.singletonList(firstV2),
+                firstChain.simpleRoute(firstUrl, firstInvokers, new RpcInvocation()));
+    }
+
+    private URL consumerUrl(String service, ModuleModel moduleModel) {
+        return URL.valueOf("dubbo://127.0.0.1:20880/" + service + "?application=router-chain-consumer")
+                .setScopeModel(moduleModel);
+    }
+
+    private Invoker<String> invoker(String service, int port, ModuleModel moduleModel) {
+        return new MockInvoker<>(
+                URL.valueOf("dubbo://127.0.0.1:" + port + "/" + service).setScopeModel(moduleModel), true);
+    }
+
+    private SingleRouterChain<String> chain(StateRouter<String> appRouter, StateRouter<String> nextRouter) {
+        return new SingleRouterChain<>(Collections.emptyList(), Arrays.asList(appRouter, nextRouter), true, null);
+    }
+
+    private static class PassThroughRouter extends AbstractStateRouter<String> {
+        PassThroughRouter(URL url) {
+            super(url);
+        }
+
+        @Override
+        protected BitList<Invoker<String>> doRoute(
+                BitList<Invoker<String>> invokers,
+                URL url,
+                Invocation invocation,
+                boolean needToPrintMessage,
+                Holder<RouterSnapshotNode<String>> nodeHolder,
+                Holder<String> messageHolder) {
+            return invokers;
+        }
+    }
+
+    private static class PortFilterRouter extends AbstractStateRouter<String> {
+        private final int port;
+
+        PortFilterRouter(URL url, int port) {
+            super(url);
+            this.port = port;
+        }
+
+        @Override
+        protected BitList<Invoker<String>> doRoute(
+                BitList<Invoker<String>> invokers,
+                URL url,
+                Invocation invocation,
+                boolean needToPrintMessage,
+                Holder<RouterSnapshotNode<String>> nodeHolder,
+                Holder<String> messageHolder) {
+            List<Invoker<String>> selected = new ArrayList<>();
+            for (Invoker<String> invoker : invokers) {
+                if (invoker.getUrl().getPort() == port) {
+                    selected.add(invoker);
+                }
+            }
+            return new BitList<>(selected);
+        }
+    }
+}