輕量級分布式 RPC 框架
RPC,即 Remote Procedure Call(遠程過程調用),說得通俗一點就是:調用遠程計算機上的服務,就像調用本地服務一樣。
RPC 可基於 HTTP 或 TCP 協議,Web Service 就是基於 HTTP 協議的 RPC,它具有良好的跨平臺性,但其性能卻不如基於 TCP 協議的 RPC。會兩方面會直接影響 RPC 的性能,一是傳輸方式,二是序列化。
輕量級分布式 RPC 框架的具體過程,該框架基於 TCP 協議
- Spring:它是最強大的依賴註入框架,也是業界的權威標準。
- Netty:它使 NIO 編程更加容易,屏蔽了 Java 底層的 NIO 細節。
- Protostuff:它基於 Protobuf 序列化框架,面向 POJO,無需編寫 .proto 文件。
- ZooKeeper:提供服務註冊與發現功能,開發分布式系統的必備選擇,同時它也具備天生的集群能力。
第一步:編寫服務接口
<!-- lang: java --> public interface HelloService { String hello(String name); }
第二步:編寫服務接口的實現類
<!-- lang: java --> @RpcService(HelloService.class) // 指定遠程接口
//使用RpcService
註解定義在服務接口的實現類上,需要對該實現類指定遠程接口,因為實現類可能會實現多個接口,一定要告訴框架哪個才是遠程接口。public class HelloServiceImpl implements HelloService { @Override public String hello(String name) { return "Hello! " + name; } }
<!-- lang: java --> @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Component // 表明可被 Spring 掃描 public @interface RpcService { Class<?> value(); }
第三步:配置服務端
服務端 Spring 配置文件名為spring.xml
,內容如下:
<!-- lang: xml --> <beans ...> <context:component-scan base-package="com.xxx.rpc.sample.server"/> <context:property-placeholder location="classpath:config.properties"/> <!-- 配置服務註冊組件 --> <bean id="serviceRegistry" class="com.xxx.rpc.registry.ServiceRegistry"> <constructor-arg name="registryAddress" value="${registry.address}"/> </bean> <!-- 配置 RPC 服務器 --> <bean id="rpcServer" class="com.xxx.rpc.server.RpcServer"> <constructor-arg name="serverAddress" value="${server.address}"/> <constructor-arg name="serviceRegistry" ref="serviceRegistry"/> </bean> </beans>
具體的配置參數在config.properties
文件中,連接本地的 ZooKeeper 服務器,並在 8000 端口上發布 RPC 服務。
<!-- lang: java --> # ZooKeeper 服務器 registry.address=127.0.0.1:2181 # RPC 服務器 server.address=127.0.0.1:8000
第四步:啟動服務器並發布服務
為了加載 Spring 配置文件來發布服務,只需編寫一個引導程序即可:
<!-- lang: java --> public class RpcBootstrap { public static void main(String[] args) { new ClassPathXmlApplicationContext("spring.xml"); } }
運行RpcBootstrap
類的main
方法即可啟動服務端,但還有兩個重要的組件尚未實現,它們分別是:ServiceRegistry
與RpcServer
第五步:實現服務註冊
使用 ZooKeeper 客戶端可輕松實現服務註冊功能,ServiceRegistry
代碼如下:
public class ServiceRegistry { private static final Logger LOGGER = LoggerFactory.getLogger(ServiceRegistry.class); private CountDownLatch latch = new CountDownLatch(1); private String registryAddress; public ServiceRegistry(String registryAddress) { this.registryAddress = registryAddress; } public void register(String data) { if (data != null) { ZooKeeper zk = connectServer(); if (zk != null) { createNode(zk, data); } } } private ZooKeeper connectServer() { ZooKeeper zk = null; try { zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getState() == Event.KeeperState.SyncConnected) { latch.countDown(); } } }); latch.await(); } catch (IOException | InterruptedException e) { LOGGER.error("", e); } return zk; } private void createNode(ZooKeeper zk, String data) { try { byte[] bytes = data.getBytes(); String path = zk.create(Constant.ZK_DATA_PATH, bytes, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); LOGGER.debug("create zookeeper node ({} => {})", path, data); } catch (KeeperException | InterruptedException e) { LOGGER.error("", e); } } }
其中,通過Constant
配置了所有的常量:
public interface Constant { int ZK_SESSION_TIMEOUT = 5000; String ZK_REGISTRY_PATH = "/registry"; String ZK_DATA_PATH = ZK_REGISTRY_PATH + "/data"; }
首先需要使用 ZooKeeper 客戶端命令行創建/registry
永久節點,用於存放所有的服務臨時節點
第六步:實現 RPC 服務器
使用 Netty 可實現一個支持 NIO 的 RPC 服務器,需要使用ServiceRegistry
註冊服務地址,RpcServer
代碼如下:
public class RpcServer implements ApplicationContextAware, InitializingBean { private static final Logger LOGGER = LoggerFactory.getLogger(RpcServer.class); private String serverAddress; private ServiceRegistry serviceRegistry; private Map<String, Object> handlerMap = new HashMap<>(); // 存放接口名與服務對象之間的映射關系 public RpcServer(String serverAddress) { this.serverAddress = serverAddress; } public RpcServer(String serverAddress, ServiceRegistry serviceRegistry) { this.serverAddress = serverAddress; this.serviceRegistry = serviceRegistry; } @Override public void setApplicationContext(ApplicationContext ctx) throws BeansException { Map<String, Object> serviceBeanMap = ctx.getBeansWithAnnotation(RpcService.class); // 獲取所有帶有 RpcService 註解的 Spring Bean if (MapUtils.isNotEmpty(serviceBeanMap)) { for (Object serviceBean : serviceBeanMap.values()) { String interfaceName = serviceBean.getClass().getAnnotation(RpcService.class).value().getName(); handlerMap.put(interfaceName, serviceBean); } } } @Override public void afterPropertiesSet() throws Exception { EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap bootstrap = new ServerBootstrap(); bootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) .childHandler(new ChannelInitializer<SocketChannel>() { @Override public void initChannel(SocketChannel channel) throws Exception { channel.pipeline() .addLast(new RpcDecoder(RpcRequest.class)) // 將 RPC 請求進行解碼(為了處理請求) .addLast(new RpcEncoder(RpcResponse.class)) // 將 RPC 響應進行編碼(為了返回響應) .addLast(new RpcHandler(handlerMap)); // 處理 RPC 請求 } }) .option(ChannelOption.SO_BACKLOG, 128) .childOption(ChannelOption.SO_KEEPALIVE, true); String[] array = serverAddress.split(":"); String host = array[0]; int port = Integer.parseInt(array[1]); ChannelFuture future = bootstrap.bind(host, port).sync(); LOGGER.debug("server started on port {}", port); if (serviceRegistry != null) { serviceRegistry.register(serverAddress); // 註冊服務地址 } future.channel().closeFuture().sync(); } finally { workerGroup.shutdownGracefully(); bossGroup.shutdownGracefully(); } } }
以上代碼中,有兩個重要的 POJO 需要描述一下,它們分別是RpcRequest
與RpcResponse
。
使用RpcRequest
封裝 RPC 請求,代碼如下:
public class RpcRequest { private String requestId; private String className; private String methodName; private Class<?>[] parameterTypes; private Object[] parameters; // getter/setter... }
使用RpcResponse
封裝 RPC 響應,代碼如下:
public class RpcResponse { private String requestId; private Throwable error; private Object result; // getter/setter... }
使用RpcDecoder
提供 RPC 解碼,只需擴展 Netty 的ByteToMessageDecoder
抽象類的decode
方法即可,代碼如下:
public class RpcDecoder extends ByteToMessageDecoder { private Class<?> genericClass; public RpcDecoder(Class<?> genericClass) { this.genericClass = genericClass; } @Override public void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception { if (in.readableBytes() < 4) { return; } in.markReaderIndex(); int dataLength = in.readInt(); if (dataLength < 0) { ctx.close(); } if (in.readableBytes() < dataLength) { in.resetReaderIndex(); return; } byte[] data = new byte[dataLength]; in.readBytes(data); Object obj = SerializationUtil.deserialize(data, genericClass); out.add(obj); } }
使用RpcEncoder
提供 RPC 編碼,只需擴展 Netty 的MessageToByteEncoder
抽象類的encode
方法即可,代碼如下:
public class RpcEncoder extends MessageToByteEncoder { private Class<?> genericClass; public RpcEncoder(Class<?> genericClass) { this.genericClass = genericClass; } @Override public void encode(ChannelHandlerContext ctx, Object in, ByteBuf out) throws Exception { if (genericClass.isInstance(in)) { byte[] data = SerializationUtil.serialize(in); out.writeInt(data.length); out.writeBytes(data); } } }
編寫一個SerializationUtil
工具類,使用Protostuff
實現序列化:
public class SerializationUtil { private static Map<Class<?>, Schema<?>> cachedSchema = new ConcurrentHashMap<>(); private static Objenesis objenesis = new ObjenesisStd(true); private SerializationUtil() { } @SuppressWarnings("unchecked") private static <T> Schema<T> getSchema(Class<T> cls) { Schema<T> schema = (Schema<T>) cachedSchema.get(cls); if (schema == null) { schema = RuntimeSchema.createFrom(cls); if (schema != null) { cachedSchema.put(cls, schema); } } return schema; } @SuppressWarnings("unchecked") public static <T> byte[] serialize(T obj) { Class<T> cls = (Class<T>) obj.getClass(); LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE); try { Schema<T> schema = getSchema(cls); return ProtostuffIOUtil.toByteArray(obj, schema, buffer); } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } finally { buffer.clear(); } } public static <T> T deserialize(byte[] data, Class<T> cls) { try { T message = (T) objenesis.newInstance(cls); Schema<T> schema = getSchema(cls); ProtostuffIOUtil.mergeFrom(data, message, schema); return message; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } }
以上了使用 Objenesis 來實例化對象,它是比 Java 反射更加強大。
註意:如需要替換其它序列化框架,只需修改SerializationUtil
即可。當然,更好的實現方式是提供配置項來決定使用哪種序列化方式。
使用RpcHandler
中處理 RPC 請求,只需擴展 Netty 的SimpleChannelInboundHandler
抽象類即可,代碼如下:
public class RpcHandler extends SimpleChannelInboundHandler<RpcRequest> { private static final Logger LOGGER = LoggerFactory.getLogger(RpcHandler.class); private final Map<String, Object> handlerMap; public RpcHandler(Map<String, Object> handlerMap) { this.handlerMap = handlerMap; } @Override public void channelRead0(final ChannelHandlerContext ctx, RpcRequest request) throws Exception { RpcResponse response = new RpcResponse(); response.setRequestId(request.getRequestId()); try { Object result = handle(request); response.setResult(result); } catch (Throwable t) { response.setError(t); } ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE); } private Object handle(RpcRequest request) throws Throwable { String className = request.getClassName(); Object serviceBean = handlerMap.get(className); Class<?> serviceClass = serviceBean.getClass(); String methodName = request.getMethodName(); Class<?>[] parameterTypes = request.getParameterTypes(); Object[] parameters = request.getParameters(); /*Method method = serviceClass.getMethod(methodName, parameterTypes); method.setAccessible(true); return method.invoke(serviceBean, parameters);*/ FastClass serviceFastClass = FastClass.create(serviceClass); FastMethod serviceFastMethod = serviceFastClass.getMethod(methodName, parameterTypes); return serviceFastMethod.invoke(serviceBean, parameters); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { LOGGER.error("server caught exception", cause); ctx.close(); } }
為了避免使用 Java 反射帶來的性能問題,我們可以使用 CGLib 提供的反射 API,如上面用到的FastClass
與FastMethod
。
第七步:配置客戶端
同樣使用 Spring 配置文件來配置 RPC 客戶端,spring.xml
代碼如下:
<!-- lang: java --> <beans ...> <context:property-placeholder location="classpath:config.properties"/> <!-- 配置服務發現組件 --> <bean id="serviceDiscovery" class="com.xxx.rpc.registry.ServiceDiscovery"> <constructor-arg name="registryAddress" value="${registry.address}"/> </bean> <!-- 配置 RPC 代理 --> <bean id="rpcProxy" class="com.xxx.rpc.client.RpcProxy"> <constructor-arg name="serviceDiscovery" ref="serviceDiscovery"/> </bean> </beans>
<!-- lang: java --> # ZooKeeper 服務器 registry.address=127.0.0.1:2181
第八步:實現服務發現
同樣使用 ZooKeeper 實現服務發現功能,見如下代碼:
public class ServiceDiscovery { private static final Logger LOGGER = LoggerFactory.getLogger(ServiceDiscovery.class); private CountDownLatch latch = new CountDownLatch(1); private volatile List<String> dataList = new ArrayList<>(); private String registryAddress; public ServiceDiscovery(String registryAddress) { this.registryAddress = registryAddress; ZooKeeper zk = connectServer(); if (zk != null) { watchNode(zk); } } public String discover() { String data = null; int size = dataList.size(); if (size > 0) { if (size == 1) { data = dataList.get(0); LOGGER.debug("using only data: {}", data); } else { data = dataList.get(ThreadLocalRandom.current().nextInt(size)); LOGGER.debug("using random data: {}", data); } } return data; } private ZooKeeper connectServer() { ZooKeeper zk = null; try { zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getState() == Event.KeeperState.SyncConnected) { latch.countDown(); } } }); latch.await(); } catch (IOException | InterruptedException e) { LOGGER.error("", e); } return zk; } private void watchNode(final ZooKeeper zk) { try { List<String> nodeList = zk.getChildren(Constant.ZK_REGISTRY_PATH, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getType() == Event.EventType.NodeChildrenChanged) { watchNode(zk); } } }); List<String> dataList = new ArrayList<>(); for (String node : nodeList) { byte[] bytes = zk.getData(Constant.ZK_REGISTRY_PATH + "/" + node, false, null); dataList.add(new String(bytes)); } LOGGER.debug("node data: {}", dataList); this.dataList = dataList; } catch (KeeperException | InterruptedException e) { LOGGER.error("", e); } } }
第九步:實現 RPC 代理
這裏使用 Java 提供的動態代理技術實現 RPC 代理(當然也可以使用 CGLib 來實現),具體代碼如下:
public class RpcProxy { private String serverAddress; private ServiceDiscovery serviceDiscovery; public RpcProxy(String serverAddress) { this.serverAddress = serverAddress; } public RpcProxy(ServiceDiscovery serviceDiscovery) { this.serviceDiscovery = serviceDiscovery; } @SuppressWarnings("unchecked") public <T> T create(Class<?> interfaceClass) { return (T) Proxy.newProxyInstance( interfaceClass.getClassLoader(), new Class<?>[]{interfaceClass}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { RpcRequest request = new RpcRequest(); // 創建並初始化 RPC 請求 request.setRequestId(UUID.randomUUID().toString()); request.setClassName(method.getDeclaringClass().getName()); request.setMethodName(method.getName()); request.setParameterTypes(method.getParameterTypes()); request.setParameters(args); if (serviceDiscovery != null) { serverAddress = serviceDiscovery.discover(); // 發現服務 } String[] array = serverAddress.split(":"); String host = array[0]; int port = Integer.parseInt(array[1]); RpcClient client = new RpcClient(host, port); // 初始化 RPC 客戶端 RpcResponse response = client.send(request); // 通過 RPC 客戶端發送 RPC 請求並獲取 RPC 響應 if (response.isError()) { throw response.getError(); } else { return response.getResult(); } } } ); } }
使用RpcClient
類實現 RPC 客戶端,只需擴展 Netty 提供的SimpleChannelInboundHandler
抽象類即可,代碼如下:
public class RpcClient extends SimpleChannelInboundHandler<RpcResponse> { private static final Logger LOGGER = LoggerFactory.getLogger(RpcClient.class); private String host; private int port; private RpcResponse response; private final Object obj = new Object(); public RpcClient(String host, int port) { this.host = host; this.port = port; } @Override public void channelRead0(ChannelHandlerContext ctx, RpcResponse response) throws Exception { this.response = response; synchronized (obj) { obj.notifyAll(); // 收到響應,喚醒線程 } } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { LOGGER.error("client caught exception", cause); ctx.close(); } public RpcResponse send(RpcRequest request) throws Exception { EventLoopGroup group = new NioEventLoopGroup(); try { Bootstrap bootstrap = new Bootstrap(); bootstrap.group(group).channel(NioSocketChannel.class) .handler(new ChannelInitializer<SocketChannel>() { @Override public void initChannel(SocketChannel channel) throws Exception { channel.pipeline() .addLast(new RpcEncoder(RpcRequest.class)) // 將 RPC 請求進行編碼(為了發送請求) .addLast(new RpcDecoder(RpcResponse.class)) // 將 RPC 響應進行解碼(為了處理響應) .addLast(RpcClient.this); // 使用 RpcClient 發送 RPC 請求 } }) .option(ChannelOption.SO_KEEPALIVE, true); ChannelFuture future = bootstrap.connect(host, port).sync(); future.channel().writeAndFlush(request).sync(); synchronized (obj) { obj.wait(); // 未收到響應,使線程等待 } if (response != null) { future.channel().closeFuture().sync(); } return response; } finally { group.shutdownGracefully(); } } }
第十步:發送 RPC 請求
使用 JUnit 結合 Spring 編寫一個單元測試,代碼如下:
@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:spring.xml") public class HelloServiceTest { @Autowired private RpcProxy rpcProxy; @Test public void helloTest() { HelloService helloService = rpcProxy.create(HelloService.class); String result = helloService.hello("World"); Assert.assertEquals("Hello! World", result); } }
本文通過 Spring + Netty + Protostuff + ZooKeeper 實現了一個輕量級 RPC 框架,使用 Spring 提供依賴註入與參數配置,使用 Netty 實現 NIO 方式的數據傳輸,使用 Protostuff 實現對象序列化,使用 ZooKeeper 實現服務註冊與發現。使用該框架,可將服務部署到分布式環境中的任意節點上,客戶端通過遠程接口來調用服務端的具體實現,讓服務端與客戶端的開發完全分離,為實現大規模分布式應用提供了基礎支持。
附錄:Maven 依賴
<!-- lang: xml --> <!-- JUnit --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <!-- SLF4J --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.7.7</version> </dependency> <!-- Spring --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>3.2.12.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>3.2.12.RELEASE</version> <scope>test</scope> </dependency> <!-- Netty --> <dependency> <groupId>io.netty</groupId> <artifactId>netty-all</artifactId> <version>4.0.24.Final</version> </dependency> <!-- Protostuff --> <dependency> <groupId>com.dyuproject.protostuff</groupId> <artifactId>protostuff-core</artifactId> <version>1.0.8</version> </dependency> <dependency> <groupId>com.dyuproject.protostuff</groupId> <artifactId>protostuff-runtime</artifactId> <version>1.0.8</version> </dependency> <!-- ZooKeeper --> <dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.4.6</version> </dependency> <!-- Apache Commons Collections --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-collections4</artifactId> <version>4.0</version> </dependency> <!-- Objenesis --> <dependency> <groupId>org.objenesis</groupId> <artifactId>objenesis</artifactId> <version>2.1</version> </dependency> <!-- CGLib --> <dependency> <groupId>cglib</groupId> <artifactId>cglib</artifactId> <version>3.1</version> </dependency>
http://javatar.iteye.com/blog/1123915
輕量級分布式 RPC 框架