学习别人的rpc框架

https://my.oschina.net/huangyong/blog/361751

https://gitee.com/huangyong/rpc

在此文基础上的另一个实现，解决了原文中一些问题，增加了一些功能

http://www.cnblogs.com/luxiaoxun/p/5272384.html

这一类同时可以参考hadoop的实现，纯异步，相当于更进一步

http://www.cnblogs.com/LBSer/p/4853234.html (๑•̀ㅂ•́)و✧

第一个链接为作者的描述，非常清晰，第二个为代码，包含以下几个功能包

自己的理解和摘取一些我认为值得记录的点

RPC：客户端发起请求，端封装请求，网络连接到某个服务端（服务治理），通过网络协议（tcp/http），序列化请求发送到服务端，服务端收到网络请求，反序列化请求本地服务，再将返回序列化，发送到客户端，客户端反序列化给本地展示结果。

http应用层协议，tcp为传输层协议，越上层的协议可能提供了越丰富的特性，越底层数据传输越快。

JAVA本身的序列化方式不管是性能还是序列化后的字节大小都不太好，所以需要根据实际情况集成其他序列化方式

服务被部署在不同的服务器节点上，需要服务发现提供注册和客户端发现功能

如何实现？通过启动类加载xml文件，启动相关组件

    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("spring.xml");
    }

<!-- lang: xml -->
<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>

服务注解标签

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Component // 表明可被 Spring 扫描
public @interface RpcService {

    Class<?> value();
}

具体的服务实现类

@RpcService(HelloService.class) // 指定远程接口
public class HelloServiceImpl implements HelloService {

    @Override
    public String hello(String name) {
        return "Hello! " + name;
    }
}

服务发现相关就是利用了zookeeper的znode/watcher

    String ZK_REGISTRY_PATH = "/registry";
    String ZK_DATA_PATH = ZK_REGISTRY_PATH + "/data";

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);
        }
    }
}

下面是NIO rpc的实现 implements ApplicationContextAware, InitializingBean

setApplicationContext处理类处理了注解指出的服务类

afterPropertiesSet 开启了服务并向注册中心注册

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();
        }
    }
}

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);
        }
    }
}

请求

public class RpcRequest {

    private String requestId;
    private String className;
    private String methodName;
    private Class<?>[] parameterTypes;
    private Object[] parameters;

    // getter/setter...
}

响应

public class RpcResponse {

    private String requestId;
    private Throwable error;
    private Object result;

    // getter/setter...
}

这里将序列化和反序列化方法集中在序列化工具中，可以自由替换成其他

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);
        }
    }
}

请求处理类handler，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，如下面用到的FastClass与FastMethod。

意思都一样，就是根据请求拿出请求相关信息，然后反射调用拿到结果构造返回

这里hadoop用的动态代理，跟这篇文章描述的这样 http://www.cnblogs.com/LBSer/p/4853234.html

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();
    }
}

客户端配置

<!-- lang: java -->
<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>

服务发现

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);
        }
    }
}

代理实现，构建服务请求信息，然后注册的服务里找一个，客户端netty将请求发送到服务端

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();
                    }
                }
            }
        );
    }
}

客户端简单实现

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();
        }
    }
}

客户端发送测试

@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);
    }
}