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RPC,即 Remote Procedure Call(远程过程调用),说得通俗一点就是:调用远程计算机上的服务,就像调用本地服务一样。
RPC 可基于 HTTP 或 TCP 协议,Web Service 就是基于 HTTP 协议的 RPC,它具有良好的跨平台性,但其性能却不如基于 TCP 协议的 RPC。会两方面会直接影响 RPC 的性能,一是传输方式,二是序列化。
众所周知,TCP 是传输层协议,HTTP 是应用层协议,而传输层较应用层更加底层,在数据传输方面,越底层越快,因此,在一般情况下,TCP 一定比 HTTP 快。就序列化而言,Java 提供了默认的序列化方式,但在高并发的情况下,这种方式将会带来一些性能上的瓶颈,于是市面上出现了一系列优秀的序列化框架,比如:Protobuf、Kryo、Hessian、Jackson 等,它们可以取代 Java 默认的序列化,从而提供更高效的性能。
为了支持高并发,传统的阻塞式 IO 显然不太合适,因此我们需要异步的 IO,即 NIO。Java 提供了 NIO 的解决方案,Java 7 也提供了更优秀的 NIO.2 支持,用 Java 实现 NIO 并不是遥不可及的事情,只是需要我们熟悉 NIO 的技术细节。
我们需要将服务部署在分布式环境下的不同节点上,通过服务注册的方式,让客户端来自动发现当前可用的服务,并调用这些服务。这需要一种服务注册表(Service Registry)的组件,让它来注册分布式环境下所有的服务地址(包括:主机名与端口号)。
应用、服务、服务注册表之间的关系见下图:
本文将为您揭晓开发轻量级分布式 RPC 框架的具体过程,该框架基于 TCP 协议,提供了 NIO 特性,提供高效的序列化方式,同时也具备服务注册与发现的能力。
根据以上技术需求,我们可使用如下技术选型:
相关 Maven 依赖请见附录。
public interface HelloService { String hello(String name); }
将该接口放在独立的客户端 jar 包中,以供应用使用。
@RpcService(HelloService.class) // 指定远程接口 public class HelloServiceImpl implements HelloService { @Override public String hello(String name) { return "Hello! " + name; } }
使用RpcService
注解定义在服务接口的实现类上,需要对该实现类指定远程接口,因为实现类可能会实现多个接口,一定要告诉框架哪个才是远程接口。
RpcService
代码如下:
@Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Component // 表明可被 Spring 扫描 public @interface RpcService { Class<?> value(); }
该注解具备 Spring 的Component
注解的特性,可被 Spring 扫描。
该实现类放在服务端 jar 包中,该 jar 包还提供了一些服务端的配置文件与启动服务的引导程序。
服务端 Spring 配置文件名为spring.xml
,内容如下:
<beans ...> <context:component-scan base-package="com.xxx.rpc.sample.server"/> <context:property-placeholder location="classpath:config.properties"/> <!-- 配置服务注册组件 --> <bean id="serviceRegistry" class="com.xxx.rpc.registry.ServiceRegistry"> <constructor-arg name="registryAddress" value="${registry.address}"/> </bean> <!-- 配置 RPC 服务器 --> <bean id="rpcServer" class="com.xxx.rpc.server.RpcServer"> <constructor-arg name="serverAddress" value="${server.address}"/> <constructor-arg name="serviceRegistry" ref="serviceRegistry"/> </bean> </beans>
具体的配置参数在config.properties
文件中,内容如下:
# ZooKeeper 服务器 registry.address=127.0.0.1:2181 # RPC 服务器 server.address=127.0.0.1:8000
以上配置表明:连接本地的 ZooKeeper 服务器,并在 8000 端口上发布 RPC 服务。
为了加载 Spring 配置文件来发布服务,只需编写一个引导程序即可:
public class RpcBootstrap { public static void main(String[] args) { new ClassPathXmlApplicationContext("spring.xml"); } }
运行RpcBootstrap
类的main
方法即可启动服务端,但还有两个重要的组件尚未实现,它们分别是:ServiceRegistry
与RpcServer
,下文会给出具体实现细节。
使用 ZooKeeper 客户端可轻松实现服务注册功能,ServiceRegistry
代码如下:
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,通过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"; }
注意:首先需要使用 ZooKeeper 客户端命令行创建/registry
永久节点,用于存放所有的服务临时节点。
使用 Netty 可实现一个支持 NIO 的 RPC 服务器,需要使用ServiceRegistry
注册服务地址,RpcServer
代码如下:
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<>(); // 存放接口名与服务对象之间的映射关系 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); // 获取所有带有 RpcService 注解的 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)) // 将 RPC 请求进行解码(为了处理请求) .addLast(new RpcEncoder(RpcResponse.class)) // 将 RPC 响应进行编码(为了返回响应) .addLast(new RpcHandler(handlerMap)); // 处理 RPC 请求 } }) .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); // 注册服务地址 } future.channel().closeFuture().sync(); } finally { workerGroup.shutdownGracefully(); bossGroup.shutdownGracefully(); } } }
以上代码中,有两个重要的 POJO 需要描述一下,它们分别是RpcRequest
与RpcResponse
。
使用RpcRequest
封装 RPC 请求,代码如下:
public class RpcRequest { private String requestId; private String className; private String methodName; private Class<?>[] parameterTypes; private Object[] parameters; // getter/setter... }
使用RpcResponse
封装 RPC 响应,代码如下:
public class RpcResponse { private String requestId; private Throwable error; private Object result; // getter/setter... }
使用RpcDecoder
提供 RPC 解码,只需扩展 Netty 的ByteToMessageDecoder
抽象类的decode
方法即可,代码如下:
public class RpcDecoder extends ByteToMessageDecoder { private Class<?> genericClass; public RpcDecoder(Class<?> genericClass) { this.genericClass = genericClass; } @Override public final 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(); } byte[] data = new byte[dataLength]; in.readBytes(data); Object obj = SerializationUtil.deserialize(data, genericClass); out.add(obj); } }
使用RpcEncoder
提供 RPC 编码,只需扩展 Netty 的MessageToByteEncoder
抽象类的encode
方法即可,代码如下:
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); } } }
编写一个SerializationUtil
工具类,使用Protostuff
实现序列化:
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 来实例化对象,它是比 Java 反射更加强大。
注意:如需要替换其它序列化框架,只需修改SerializationUtil
即可。当然,更好的实现方式是提供配置项来决定使用哪种序列化方式。
使用RpcHandler
中处理 RPC 请求,只需扩展 Netty 的SimpleChannelInboundHandler
抽象类即可,代码如下:
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(); } }
为了避免使用 Java 反射带来的性能问题,我们可以使用 CGLib 提供的反射 API,如上面用到的FastClass
与FastMethod
。
同样使用 Spring 配置文件来配置 RPC 客户端,spring.xml
代码如下:
<beans ...> <context:property-placeholder location="classpath:config.properties"/> <!-- 配置服务发现组件 --> <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>
其中config.properties
提供了具体的配置:
# ZooKeeper 服务器 registry.address=127.0.0.1:2181
同样使用 ZooKeeper 实现服务发现功能,见如下代码:
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); } } }
这里使用 Java 提供的动态代理技术实现 RPC 代理(当然也可以使用 CGLib 来实现),具体代码如下:
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(); // 创建并初始化 RPC 请求 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(); // 发现服务 } String[] array = serverAddress.split(":"); String host = array[0]; int port = Integer.parseInt(array[1]); RpcClient client = new RpcClient(host, port); // 初始化 RPC 客户端 RpcResponse response = client.send(request); // 通过 RPC 客户端发送 RPC 请求并获取 RPC 响应 if (response.isError()) { throw response.getError(); } else { return response.getResult(); } } } ); } }
使用RpcClient
类实现 RPC 客户端,只需扩展 Netty 提供的SimpleChannelInboundHandler
抽象类即可,代码如下:
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(); // 收到响应,唤醒线程 } } @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)) // 将 RPC 请求进行编码(为了发送请求) .addLast(new RpcDecoder(RpcResponse.class)) // 将 RPC 响应进行解码(为了处理响应) .addLast(RpcClient.this); // 使用 RpcClient 发送 RPC 请求 } }) .option(ChannelOption.SO_KEEPALIVE, true); ChannelFuture future = bootstrap.connect(host, port).sync(); future.channel().writeAndFlush(request).sync(); synchronized (obj) { obj.wait(); // 未收到响应,使线程等待 } if (response != null) { future.channel().closeFuture().sync(); } return response; } finally { group.shutdownGracefully(); } } }
使用 JUnit 结合 Spring 编写一个单元测试,代码如下:
@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); } }
运行以上单元测试,如果不出意外的话,您应该会看到绿条。
本文通过 Spring + Netty + Protostuff + ZooKeeper 实现了一个轻量级 RPC 框架,使用 Spring 提供依赖注入与参数配置,使用 Netty 实现 NIO 方式的数据传输,使用 Protostuff 实现对象序列化,使用 ZooKeeper 实现服务注册与发现。使用该框架,可将服务部署到分布式环境中的任意节点上,客户端通过远程接口来调用服务端的具体实现,让服务端与客户端的开发完全分离,为实现大规模分布式应用提供了基础支持。
<!-- 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>
源码地址:http://www.oschina.net/code/snippet_223750_45050
http://my.oschina.net/huangyong/blog/361751
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原文地址:http://www.cnblogs.com/549294286/p/4603441.html