引入TagRouter

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/Router.java

@@ -51,4 +51,11 @@ public interface Router extends Comparable<Router> {
      */
     <T> List<Invoker<T>> route(List<Invoker<T>> invokers, URL url, Invocation invocation) throws RpcException;
 
+    /**
+     * router priority
+     *
+     * @return
+     */
+    int getPriority();
+
 }

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/AbstractRouter.java

@@ -0,0 +1,25 @@
+package com.alibaba.dubbo.rpc.cluster.router;
+
+import com.alibaba.dubbo.common.URL;
+import com.alibaba.dubbo.rpc.cluster.Router;
+
+public abstract class AbstractRouter implements Router {
+
+    protected int priority;
+    protected URL url;
+
+    @Override
+    public URL getUrl() {
+        return url;
+    }
+
+    @Override
+    public int getPriority() {
+        return priority;
+    }
+
+    @Override
+    public int compareTo(Router o) {
+        return (this.getPriority() >= o.getPriority()) ? 1 : -1;
+    }
+}

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/MockInvokersSelector.java

@@ -31,7 +31,7 @@
  * If a request is configured to use mock, then this router guarantees that only the invokers with protocol MOCK appear in final the invoker list, all other invokers will be excluded.
  *
  */
-public class MockInvokersSelector implements Router {
+public class MockInvokersSelector extends AbstractRouter {
 
     @Override
     public <T> List<Invoker<T>> route(final List<Invoker<T>> invokers,
@@ -87,11 +87,12 @@ private <T> boolean hasMockProviders(final List<Invoker<T>> invokers) {
         return hasMockProvider;
     }
 
-    @Override
-    public URL getUrl() {
-        return null;
-    }
-
+    /**
+     * Always stay on the top of the list
+     *
+     * @param o
+     * @return
+     */
     @Override
     public int compareTo(Router o) {
         return 1;

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/condition/ConditionRouter.java

@@ -26,7 +26,7 @@
 import com.alibaba.dubbo.rpc.Invocation;
 import com.alibaba.dubbo.rpc.Invoker;
 import com.alibaba.dubbo.rpc.RpcException;
-import com.alibaba.dubbo.rpc.cluster.Router;
+import com.alibaba.dubbo.rpc.cluster.router.AbstractRouter;
 
 import java.text.ParseException;
 import java.util.ArrayList;
@@ -42,12 +42,10 @@
  * ConditionRouter
  *
  */
-public class ConditionRouter implements Router, Comparable<Router> {
+public class ConditionRouter extends AbstractRouter {
 
     private static final Logger logger = LoggerFactory.getLogger(ConditionRouter.class);
     private static Pattern ROUTE_PATTERN = Pattern.compile("([&!=,]*)\\s*([^&!=,\\s]+)");
-    private final URL url;
-    private final int priority;
     private final boolean force;
     private final Map<String, MatchPair> whenCondition;
     private final Map<String, MatchPair> thenCondition;
@@ -174,20 +172,6 @@ public <T> List<Invoker<T>> route(List<Invoker<T>> invokers, URL url, Invocation
         return invokers;
     }
 
-    @Override
-    public URL getUrl() {
-        return url;
-    }
-
-    @Override
-    public int compareTo(Router o) {
-        if (o == null || o.getClass() != ConditionRouter.class) {
-            return 1;
-        }
-        ConditionRouter c = (ConditionRouter) o;
-        return this.priority == c.priority ? url.toFullString().compareTo(c.url.toFullString()) : (this.priority > c.priority ? 1 : -1);
-    }
-
     boolean matchWhen(URL url, Invocation invocation) {
         return whenCondition == null || whenCondition.isEmpty() || matchCondition(whenCondition, url, null, invocation);
     }

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/script/ScriptRouter.java

@@ -24,7 +24,7 @@
 import com.alibaba.dubbo.rpc.Invoker;
 import com.alibaba.dubbo.rpc.RpcContext;
 import com.alibaba.dubbo.rpc.RpcException;
-import com.alibaba.dubbo.rpc.cluster.Router;
+import com.alibaba.dubbo.rpc.cluster.router.AbstractRouter;
 
 import javax.script.Bindings;
 import javax.script.Compilable;
@@ -42,20 +42,16 @@
  * ScriptRouter
  *
  */
-public class ScriptRouter implements Router {
+public class ScriptRouter extends AbstractRouter {
 
     private static final Logger logger = LoggerFactory.getLogger(ScriptRouter.class);
 
     private static final Map<String, ScriptEngine> engines = new ConcurrentHashMap<String, ScriptEngine>();
 
     private final ScriptEngine engine;
 
-    private final int priority;
-
     private final String rule;
 
-    private final URL url;
-
     public ScriptRouter(URL url) {
         this.url = url;
         String type = url.getParameter(Constants.TYPE_KEY);
@@ -79,11 +75,6 @@ public ScriptRouter(URL url) {
         this.rule = rule;
     }
 
-    @Override
-    public URL getUrl() {
-        return url;
-    }
-
     @Override
     @SuppressWarnings("unchecked")
     public <T> List<Invoker<T>> route(List<Invoker<T>> invokers, URL url, Invocation invocation) throws RpcException {
@@ -114,13 +105,4 @@ public <T> List<Invoker<T>> route(List<Invoker<T>> invokers, URL url, Invocation
         }
     }
 
-    @Override
-    public int compareTo(Router o) {
-        if (o == null || o.getClass() != ScriptRouter.class) {
-            return 1;
-        }
-        ScriptRouter c = (ScriptRouter) o;
-        return this.priority == c.priority ? rule.compareTo(c.rule) : (this.priority > c.priority ? 1 : -1);
-    }
-
 }

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/tag/TagRouter.java

@@ -0,0 +1,89 @@
+/*
+ * 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 com.alibaba.dubbo.rpc.cluster.router.tag;
+
+import com.alibaba.dubbo.common.Constants;
+import com.alibaba.dubbo.common.URL;
+import com.alibaba.dubbo.common.logger.Logger;
+import com.alibaba.dubbo.common.logger.LoggerFactory;
+import com.alibaba.dubbo.common.utils.StringUtils;
+import com.alibaba.dubbo.rpc.Invocation;
+import com.alibaba.dubbo.rpc.Invoker;
+import com.alibaba.dubbo.rpc.RpcContext;
+import com.alibaba.dubbo.rpc.RpcException;
+import com.alibaba.dubbo.rpc.cluster.router.AbstractRouter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * TagRouter
+ */
+public class TagRouter extends AbstractRouter {
+
+    private static final Logger logger = LoggerFactory.getLogger(TagRouter.class);
+    private static final int DEFAULT_PRIORITY = 100;
+    private static final URL ROUTER_URL = new URL("tag", Constants.ANYHOST_VALUE, 0, Constants.ANY_VALUE).addParameters(Constants.RUNTIME_KEY, "true");
+
+    public TagRouter(URL url) {
+        this.url = url;
+        this.priority = url.getParameter(Constants.PRIORITY_KEY, DEFAULT_PRIORITY);
+    }
+
+    public TagRouter() {
+        this.url = ROUTER_URL;
+        this.priority = url.getParameter(Constants.PRIORITY_KEY, DEFAULT_PRIORITY);
+    }
+
+    @Override
+    public URL getUrl() {
+        return url;
+    }
+
+    @Override
+    public <T> List<Invoker<T>> route(List<Invoker<T>> invokers, URL url, Invocation invocation) throws RpcException {
+        // filter
+        List<Invoker<T>> result = new ArrayList<Invoker<T>>();
+        try {
+            // Dynamic param
+            String tag = RpcContext.getContext().getAttachment(Constants.REQUEST_TAG_KEY);
+            // Tag request
+            if (!StringUtils.isEmpty(tag)) {
+                // Select tag invokers first
+                for (Invoker<T> invoker : invokers) {
+                    if (tag.equals(invoker.getUrl().getParameter(Constants.TAG_KEY))) {
+                        result.add(invoker);
+                    }
+                }
+            }
+            // If Constants.REQUEST_TAG_KEY unspecified or no invoker be selected, downgrade to normal invokers
+            if (result.isEmpty()) {
+                for (Invoker<T> invoker : invokers) {
+                    if (StringUtils.isEmpty(invoker.getUrl().getParameter(Constants.TAG_KEY))) {
+                        result.add(invoker);
+                    }
+                }
+            }
+            return result;
+        } catch (Exception e) {
+            logger.error("Route by tag error,return all invokers.", e);
+        }
+        // Downgrade to all invokers
+        return invokers;
+    }
+
+}

dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/router/tag/TagRouterFactory.java

@@ -0,0 +1,31 @@
+/*
+ * 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 com.alibaba.dubbo.rpc.cluster.router.tag;
+
+import com.alibaba.dubbo.common.URL;
+import com.alibaba.dubbo.rpc.cluster.Router;
+import com.alibaba.dubbo.rpc.cluster.RouterFactory;
+
+public class TagRouterFactory implements RouterFactory {
+
+    public static final String NAME = "tag";
+
+    @Override
+    public Router getRouter(URL url) {
+        return new TagRouter(url);
+    }
+}

dubbo-cluster/src/main/resources/META-INF/dubbo/internal/com.alibaba.dubbo.rpc.cluster.RouterFactory

@@ -1,3 +1,4 @@
 file=com.alibaba.dubbo.rpc.cluster.router.file.FileRouterFactory
 script=com.alibaba.dubbo.rpc.cluster.router.script.ScriptRouterFactory
-condition=com.alibaba.dubbo.rpc.cluster.router.condition.ConditionRouterFactory
+condition=com.alibaba.dubbo.rpc.cluster.router.condition.ConditionRouterFactory
+tag=com.alibaba.dubbo.rpc.cluster.router.tag.TagRouterFactory