Polish apache#3946 : Dubbo Cloud Native : To Add Dubbo metadata service

dubbo-all/pom.xml

@@ -509,6 +509,14 @@
             <optional>true</optional>
         </dependency>
 
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-metadata</artifactId>
+            <version>${project.version}</version>
+            <scope>compile</scope>
+            <optional>true</optional>
+        </dependency>
+
         <!-- Transitive dependencies -->
         <dependency>
             <groupId>org.springframework</groupId>
@@ -643,6 +651,7 @@
 
                                     <!-- 2.7.2 new modules -->
                                     <include>org.apache.dubbo:dubbo-event</include>
+                                    <include>org.apache.dubbo:dubbo-metadata</include>
                                 </includes>
                             </artifactSet>
                             <transformers>
@@ -773,6 +782,14 @@
                                     <resource>META-INF/dubbo/internal/org.apache.dubbo.event.EventDispatcher
                                     </resource>
                                 </transformer>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
+                                    <resource>META-INF/dubbo/internal/org.apache.dubbo.metadata.export.MetadataServiceExporter
+                                    </resource>
+                                </transformer>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
+                                    <resource>META-INF/dubbo/internal/org.apache.dubbo.metadata.LocalMetadataService
+                                    </resource>
+                                </transformer>
                             </transformers>
                             <filters>
                                 <filter>

dubbo-metadata/pom.xml

@@ -0,0 +1,59 @@
+<!--
+  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.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <groupId>org.apache.dubbo</groupId>
+        <artifactId>dubbo-parent</artifactId>
+        <version>${revision}</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>dubbo-metadata</artifactId>
+    <packaging>jar</packaging>
+
+    <name>dubbo-metadata</name>
+    <description>The metadata module of Dubbo project</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-config-api</artifactId>
+            <version>${revision}</version>
+            <optional>true</optional>
+        </dependency>
+
+        <!-- Test dependencies -->
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-rpc-dubbo</artifactId>
+            <version>${revision}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.dubbo</groupId>
+            <artifactId>dubbo-remoting-netty4</artifactId>
+            <version>${revision}</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+</project>

dubbo-metadata/src/main/java/org/apache/dubbo/metadata/InMemoryLocalMetadataService.java

@@ -0,0 +1,157 @@
+/*
+ * 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.metadata;
+
+import org.apache.dubbo.common.URL;
+
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.stream.Collectors;
+
+import static java.util.Collections.unmodifiableList;
+import static org.apache.dubbo.common.URL.buildKey;
+import static org.apache.dubbo.common.constants.CommonConstants.PROTOCOL_KEY;
+
+/**
+ * The {@link LocalMetadataService} implementation stores the metadata of Dubbo services in memory locally when they
+ * exported.
+ *
+ * @see MetadataService
+ * @since 2.7.2
+ */
+public class InMemoryLocalMetadataService implements LocalMetadataService {
+
+    /**
+     * The class name of {@link MetadataService}
+     */
+    static final String METADATA_SERVICE_CLASS_NAME = MetadataService.class.getName();
+
+    // =================================== Registration =================================== //
+
+    /**
+     * All exported {@link URL urls} {@link Map} whose key is the return value of {@link URL#getServiceKey()} method
+     * and value is the {@link List} of the {@link URL URLs}
+     */
+    private ConcurrentMap<String, List<URL>> exportedServiceURLs = new ConcurrentHashMap<>();
+
+    // ==================================================================================== //
+
+    // =================================== Subscription =================================== //
+
+    /**
+     * All subscribed service names
+     */
+    private Set<String> subscribedServices = new LinkedHashSet<>();
+
+    /**
+     * The subscribed {@link URL urls} {@link Map} of {@link MetadataService},
+     * whose key is the return value of {@link URL#getServiceKey()} method and value is the {@link List} of
+     * the {@link URL URLs}
+     */
+    private final ConcurrentMap<String, List<URL>> subscribedServiceURLs = new ConcurrentHashMap<>();
+
+    // ==================================================================================== //
+
+    @Override
+    public List<String> getSubscribedURLs() {
+        return getAllServiceURLs(subscribedServiceURLs);
+    }
+
+    @Override
+    public List<String> getExportedURLs(String serviceInterface, String group, String version, String protocol) {
+        if (ALL_SERVICE_INTERFACES.equals(serviceInterface)) {
+            return getAllServiceURLs(exportedServiceURLs);
+        }
+        String serviceKey = buildKey(serviceInterface, group, version);
+        return unmodifiableList(getServiceURLs(exportedServiceURLs, serviceKey, protocol));
+    }
+
+    protected List<String> getServiceURLs(ConcurrentMap<String, List<URL>> exportedServiceURLs, String serviceKey,
+                                          String protocol) {
+        List<URL> serviceURLs = getServiceURLs(exportedServiceURLs, serviceKey);
+        return serviceURLs.stream().filter(
+                url -> protocol == null || protocol.equals(url.getParameter(PROTOCOL_KEY)))
+                .map(URL::toFullString)
+                .collect(Collectors.toList());
+    }
+
+
+    private boolean isMetadataServiceURL(URL url) {
+        String serviceInterface = url.getServiceInterface();
+        return METADATA_SERVICE_CLASS_NAME.equals(serviceInterface);
+    }
+
+    @Override
+    public boolean exportURL(URL url) {
+        if (isMetadataServiceURL(url)) { // ignore MetadataService in the export phase
+            return true;
+        }
+        return addURL(exportedServiceURLs, url);
+    }
+
+    @Override
+    public boolean unexportURL(URL url) {
+        if (isMetadataServiceURL(url)) { // ignore MetadataService in the export phase
+            return true;
+        }
+        return removeURL(exportedServiceURLs, url);
+    }
+
+    @Override
+    public boolean subscribeURL(URL url) {
+        return addURL(subscribedServiceURLs, url);
+    }
+
+    @Override
+    public boolean unsubscribeURL(URL url) {
+        return removeURL(subscribedServiceURLs, url);
+    }
+
+    protected boolean addURL(Map<String, List<URL>> serviceURLs, URL url) {
+        String serviceKey = url.getServiceKey();
+        List<URL> urls = getServiceURLs(serviceURLs, serviceKey);
+        if (!urls.contains(url)) {
+            return urls.add(url);
+        }
+        return false;
+    }
+
+    protected boolean removeURL(Map<String, List<URL>> serviceURLs, URL url) {
+        String serviceKey = url.getServiceKey();
+        List<URL> urls = getServiceURLs(serviceURLs, serviceKey);
+        return urls.remove(url);
+    }
+
+    protected List<URL> getServiceURLs(Map<String, List<URL>> serviceURLs, String serviceKey) {
+        return serviceURLs.computeIfAbsent(serviceKey, s -> new LinkedList());
+    }
+
+    protected List<String> getAllServiceURLs(Map<String, List<URL>> serviceURLs) {
+        return serviceURLs
+                .values()
+                .stream()
+                .flatMap(Collection::stream)
+                .map(URL::toFullString)
+                .collect(Collectors.toList());
+    }
+}

dubbo-metadata/src/main/java/org/apache/dubbo/metadata/LocalMetadataService.java

@@ -0,0 +1,88 @@
+/*
+ * 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.metadata;
+
+import org.apache.dubbo.common.URL;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.extension.SPI;
+import org.apache.dubbo.rpc.model.ApplicationModel;
+
+import static org.apache.dubbo.common.extension.ExtensionLoader.getExtensionLoader;
+
+/**
+ * Local {@link MetadataService} that extends {@link MetadataService} and provides the modification, which is used for
+ * Dubbo's consumers and providers.
+ *
+ * @since 2.7.2
+ */
+@SPI("default")
+public interface LocalMetadataService extends MetadataService {
+
+    /**
+     * Gets the current Dubbo Service name
+     *
+     * @return non-null
+     */
+    @Override
+    default String serviceName() {
+        return ApplicationModel.getApplication();
+    }
+
+    /**
+     * Exports a {@link URL}
+     *
+     * @param url a {@link URL}
+     * @return If success , return <code>true</code>
+     */
+    boolean exportURL(URL url);
+
+    /**
+     * Unexports a {@link URL}
+     *
+     * @param url a {@link URL}
+     * @return If success , return <code>true</code>
+     */
+    boolean unexportURL(URL url);
+
+    /**
+     * Subscribes a {@link URL}
+     *
+     * @param url a {@link URL}
+     * @return If success , return <code>true</code>
+     */
+    boolean subscribeURL(URL url);
+
+    /**
+     * Unsubscribes a {@link URL}
+     *
+     * @param url a {@link URL}
+     * @return If success , return <code>true</code>
+     */
+    boolean unsubscribeURL(URL url);
+
+
+    /**
+     * Get {@link ExtensionLoader#getDefaultExtension() the defautl extension} of {@link LocalMetadataService}
+     *
+     * @return non-null
+     * @see InMemoryLocalMetadataService
+     */
+    public static LocalMetadataService getDefaultExtension() {
+        return getExtensionLoader(LocalMetadataService.class).getDefaultExtension();
+    }
+
+}