本文从开发者的角度深入解析了基于netty的通信模块, 并通过简易扩展实现微服务化通信工具雏形, 适合于想要了解netty通信框架的使用案例, 想了解中间件通信模块设计, 以及微服务通信底层架构的同学。希望此文能给大家带来通信模块架构灵感。
概述
网络通信是很常见的需求，
对于传统web网页工具短连接场景，浏览器和服务器交互，常见为浏览器通过http协议请求Tomcat服务器；
对于长连接场景, 比如即时通讯，或中间件等实时性要求高的场景，一般采用tcp协议的长连接进行全双工实时通信；
对于java开发者来说，使用原生socket进行tcp开发，效率是比较低的，稳定性可靠性等也不好保障，一般选择网络通信框架netty加快开发效率。
对于上层应用来说，netty的标准使用方式依然比较繁琐，未能很好的适配一些业务使用场景，比如rocketMq根据netty包装了一层业务框架：通信模块remoting。
该模块可用性高，稳定性好，易扩展，经过了中间件产品长期高并发的质量验证， 值得信任，并广泛用于其他点对点（指定ip）通信场景，如dleger(raft的java实现)。
有相关通信需求的同学也都可以参考该通信模块，相信有很多的灵感，或直接使用该通信模块，带来开发效率的提升。
本文从一个普通java开发者的视角，去解析该通信模块
如何用 - 常见使用方式
实现原理 - 数据流转链路
设计关键点 - 为什么要如此设计
模块升级 - 实现简易的微服务化通信工具
本文代码版本：
<parent><groupId>org.apache.rocketmq</groupId><artifactId>rocketmq-remoting</artifactId><version>5.0.1-PREVIEW-SNAPSHOT</version>
</parent>
如何用
编写简单易懂的测试demo，实现server client的交互流程。
简单示例 协议code 为写死 0 1 5 9，输入测试信息，输出使用sysout。
▐ 启动server 注册服务监听
import com.alibaba.fastjson.JSON;
import io.netty.channel.ChannelHandlerContext;
import org.apache.rocketmq.remoting.RemotingServer;
import org.apache.rocketmq.remoting.netty.NettyRemotingServer;
import org.apache.rocketmq.remoting.netty.NettyRequestProcessor;
import org.apache.rocketmq.remoting.netty.NettyServerConfig;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class Server {public static void main(String[] args) throws Exception {NettyServerConfig nettyServerConfig = new NettyServerConfig();// 配置端口nettyServerConfig.setListenPort(8888);// 配置线程数 netty workGroup 线程池 处理io等低耗时nettyServerConfig.setServerSelectorThreads(2);// 配置线程数 netty eventGroup 线程池 处理自定义hander/长耗时等nettyServerConfig.setServerWorkerThreads(8);NettyRemotingServer remotingServer = new NettyRemotingServer(nettyServerConfig, null);// 支持共用或独立的业务处理线程池ExecutorService poolA = new ThreadPoolExecutor(4, 4, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(1024));ExecutorService poolB = new ThreadPoolExecutor(4, 4, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(1024));// 业务处理器NettyRequestProcessor processA = new NettyRequestProcessor() {@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {System.out.println("received from client, remark:" + request.getRemark() + ", coe:" + request.getCode());RemotingCommand response = RemotingCommand.createResponseCommand(0, "server");switch (request.getCode()) {case 0:response.setBody(new String("hello sync 0").getBytes());case 1:response.setBody(new String("hello sync 1").getBytes());default:break;}return response;}@Overridepublic boolean rejectRequest() {return false;}};// 业务处理器NettyRequestProcessor processB = new NettyRequestProcessor(){@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {System.out.println("received from client, remark:" + request.getRemark() + ", coe:" + request.getCode());RemotingCommand response = RemotingCommand.createResponseCommand(0, "server");switch (request.getCode()) {case 9:response.setBody(new String("hello sync 9").getBytes());default:break;}return response;}@Overridepublic boolean rejectRequest() {return false;}};// 注册 协议 - 对应的处理器, 类似web url 路由到对应的classremotingServer.registerProcessor(0, processA, poolA);remotingServer.registerProcessor(1, processA, poolA);remotingServer.registerProcessor(9, processB, poolB);remotingServer.start();System.out.println("start ok " + JSON.toJSONString(nettyServerConfig));System.in.read();}
}▐ 启动client 发起调用
import io.netty.channel.ChannelHandlerContext;
import org.apache.rocketmq.remoting.InvokeCallback;
import org.apache.rocketmq.remoting.netty.NettyClientConfig;
import org.apache.rocketmq.remoting.netty.NettyRemotingClient;
import org.apache.rocketmq.remoting.netty.NettyRequestProcessor;
import org.apache.rocketmq.remoting.netty.ResponseFuture;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class Client {public static void main(String[] args) throws Exception {NettyClientConfig nettyServerConfig = new NettyClientConfig();// 配置线程数 netty eventGroup 线程池 处理自定义hander/耗时长等nettyServerConfig.setClientWorkerThreads(8);NettyRemotingClient remotingClient = new NettyRemotingClient(nettyServerConfig, null);// 支持共用或独立的业务处理线程池ExecutorService poolA = new ThreadPoolExecutor(4, 4, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(1024));// 监听服务端发过来的请求remotingClient.registerProcessor(5, new NettyRequestProcessor() {@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {System.out.println("receive from server : " + request.getCode());return null;}@Overridepublic boolean rejectRequest() {return false;}}, poolA);remotingClient.start();// 主动发起远程调用 {// 同步调用RemotingCommand request = RemotingCommand.createRequestCommand(0, null);request.setRemark("sync");RemotingCommand response = remotingClient.invokeSync("127.0.0.1:8888", request, 30 * 1000L);System.out.println("call sync ok remark:" + response.getRemark() + " body:" + new String(response.getBody()));}{// 异步调用RemotingCommand request = RemotingCommand.createRequestCommand(1, null);request.setRemark("async");remotingClient.invokeAsync("127.0.0.1:8888", request, 30 * 1000L, new InvokeCallback() {@Overridepublic void operationComplete(ResponseFuture responseFuture) {RemotingCommand response = responseFuture.getResponseCommand();System.out.println("call async ok remark:" + response.getRemark() + " body:" + new String(response.getBody()));}});}{// 单向调用RemotingCommand request = RemotingCommand.createRequestCommand(9, null);request.setRemark("oneway");remotingClient.invokeOneway("127.0.0.1:8888", request, 30 * 1000L);System.out.println("call oneway ok ");}System.in.read();}
}该点对点调用，是需要手动指定目标服务器的ip和端口的，不同于hsf拥有注册中心进行协调撮合提供目标ip。
▐ 日志输出
Connected to the target VM, address: '127.0.0.1:57381', transport: 'socket'
start ok {"listenPort":8888,"serverAsyncSemaphoreValue":64,"serverCallbackExecutorThreads":0,"serverChannelMaxIdleTimeSeconds":120,"serverOnewaySemaphoreValue":256,"serverPooledByteBufAllocatorEnable":true,"serverSelectorThreads":2,"serverSocketRcvBufSize":65535,"serverSocketSndBufSize":65535,"serverWorkerThreads":8,"useEpollNativeSelector":false}
received from client, remark:sync, coe:0
received from client, remark:async, coe:1
received from client, remark:oneway, coe:9Connected to the target VM, address: '127.0.0.1:57385', transport: 'socket'
call sync ok remark:server body:hello sync 1
call oneway ok
call async ok remark:server body:hello sync 1
实现原理
关于netty如何封装java基础nio socket不做展开。
这里分析通信模块是如何封装netty，扩展调用协议规范的部分，重点描述其中关键的设计要点。
▐ server 启动 监听请求
作为服务端，需绑定端口，监听请求，这里采用标准netty服务端模式。
remotingServer.start();
@Overridepublic void start() {...ServerBootstrap childHandler =this.serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupSelector).channel(useEpoll() ? EpollServerSocketChannel.class : NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024).option(ChannelOption.SO_REUSEADDR, true).option(ChannelOption.SO_KEEPALIVE, false).childOption(ChannelOption.TCP_NODELAY, true).childOption(ChannelOption.SO_SNDBUF, nettyServerConfig.getServerSocketSndBufSize()).childOption(ChannelOption.SO_RCVBUF, nettyServerConfig.getServerSocketRcvBufSize()).localAddress(new InetSocketAddress(this.nettyServerConfig.getListenPort())).childHandler(new ChannelInitializer<SocketChannel>() {@Overridepublic void initChannel(SocketChannel ch) throws Exception {
ch.pipeline()
.addLast(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, handshakeHandler)
.addLast(defaultEventExecutorGroup,encoder,new NettyDecoder(),new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),connectionManageHandler,serverHandler
);}});...ChannelFuture sync = this.serverBootstrap.bind().sync();InetSocketAddress addr = (InetSocketAddress) sync.channel().localAddress();...}关注涉及几个线程池的地方：
bossGroup -> eventLoopGroupBoss 固定线程数1
workerGroup -> eventLoopGroupSelector 若linux采用epoll实现 否则使用nio实现, 线程数可配置
eventGroup -> defaultEventExecutorGroup 普通实现的 handler 工作线程池, 线程数可配置
另外就是传统艺能：心跳, 解码器 NettyEncoder，编码器 NettyDecoder，连接管理器 connectionManageHandler，和最终的业务处理器 serverHandler
▐ server 注册业务处理器
业务线程池配置
请求协议code关联业务处理器
// 支持共用或独立的业务处理线程池ExecutorService poolA = new ThreadPoolExecutor(4, 4, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(1024));ExecutorService poolB = new ThreadPoolExecutor(4, 4, 0, TimeUnit.SECONDS, new ArrayBlockingQueue<>(1024));// 业务处理器NettyRequestProcessor processA = new NettyRequestProcessor() {@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {System.out.println("received from client, remark:" + request.getRemark() + ", coe:" + request.getCode());RemotingCommand response = RemotingCommand.createResponseCommand(0, "server");switch (request.getCode()) {case 0:response.setBody(new String("hello sync 0").getBytes());case 1:response.setBody(new String("hello sync 1").getBytes());default:break;}return response;}@Overridepublic boolean rejectRequest() {return false;}};// 业务处理器NettyRequestProcessor processB = new NettyRequestProcessor(){@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {System.out.println("received from client, remark:" + request.getRemark() + ", coe:" + request.getCode());RemotingCommand response = RemotingCommand.createResponseCommand(0, "server");switch (request.getCode()) {case 9:response.setBody(new String("hello sync 9").getBytes());default:break;}return response;}@Overridepublic boolean rejectRequest() {return false;}};// 注册 协议 - 对应的处理器, 类似web url 路由到对应的classremotingServer.registerProcessor(0, processA, poolA);remotingServer.registerProcessor(1, processA, poolA);remotingServer.registerProcessor(9, processB, poolB);不同业务独立线程池的必要性
在复杂业务场景中，比如商品管理链路，订单交易链路，将所有的请求堆积在一个线程池中，快请求和慢请求公用一个赛道，无法避免资源分配不均问题
通信模块设计为可手动配置每个业务的处理线程池
注册路由和线程池关系
@Overridepublic void registerProcessor(int requestCode, NettyRequestProcessor processor, ExecutorService executor) {ExecutorService executorThis = executor;if (null == executor) {executorThis = this.publicExecutor;}Pair<NettyRequestProcessor, ExecutorService> pair = new Pair<NettyRequestProcessor, ExecutorService>(processor, executorThis);this.processorTable.put(requestCode, pair);}建立 code - processor - pool 的三者映射关系，在后续收到请求后，可查找注册关系进行路由唤起processor
▐ client 启动 发起请求
NettyRemotingClient remotingClient = new NettyRemotingClient(nettyServerConfig, null);remotingClient.start();// 主动发起远程调用{// 同步调用RemotingCommand request = RemotingCommand.createRequestCommand(0, null);request.setRemark("sync");RemotingCommand response = remotingClient.invokeSync("127.0.0.1:8888", request, 30 * 1000L);System.out.println("call sync ok remark:" + response.getRemark() + " body:" + new String(response.getBody()));}{// 异步调用RemotingCommand request = RemotingCommand.createRequestCommand(1, null);request.setRemark("async");remotingClient.invokeAsync("127.0.0.1:8888", request, 30 * 1000L, new InvokeCallback() {@Overridepublic void operationComplete(ResponseFuture responseFuture) {RemotingCommand response = responseFuture.getResponseCommand();System.out.println("call async ok remark:" + response.getRemark() + " body:" + new String(response.getBody()));}});}{// 单向调用RemotingCommand request = RemotingCommand.createRequestCommand(9, null);request.setRemark("oneway");remotingClient.invokeOneway("127.0.0.1:8888", request, 30 * 1000L);System.out.println("call oneway ok ");}启动客户端client后，即处于长连接状态，双向通信及时性有保障
三种调用模式
作为通信组件，需要适配多种调用场景，同步异步调用已是基本操作，oneway用于不关心是否返回的场景。
试想一下，在全双工双向异步通信的背景下，如何能像http一样实现同步调用，发出一个请求，收到一个请求后怎么跟前面发出的请求关联起来，又如何实现异步等待转为同步响应。
同步调用
发起请求
public RemotingCommand invokeSyncImpl(final Channel channel, final RemotingCommand request, final long timeoutMillis)throws InterruptedException, RemotingSendRequestException, RemotingTimeoutException {// 唯一idfinal int opaque = request.getOpaque(); ...final ResponseFuture responseFuture = new ResponseFuture(channel, opaque, timeoutMillis, null, null);// 把当前请求记录到待响应table中this.responseTable.put(opaque, responseFuture);final SocketAddress addr = channel.remoteAddress();channel.writeAndFlush(request).addListener(new ChannelFutureListener() {@Overridepublic void operationComplete(ChannelFuture f) throws Exception {if (f.isSuccess()) {//标记为写入成功responseFuture.setSendRequestOK(true);return;} else {responseFuture.setSendRequestOK(false);}// 写入异常结果 并唤起wait的线程responseTable.remove(opaque);responseFuture.setCause(f.cause());responseFuture.putResponse(null);public void putResponse(final RemotingCommand responseCommand) {this.responseCommand = responseCommand;this.countDownLatch.countDown();}log.warn("send a request command to channel <" + addr + "> failed.");}});// 同步等待结果RemotingCommand responseCommand = responseFuture.waitResponse(timeoutMillis);public RemotingCommand waitResponse(final long timeoutMillis) throws InterruptedException {this.countDownLatch.await(timeoutMillis, TimeUnit.MILLISECONDS);return this.responseCommand;}...}关键设计点：每一个请求request，都分配了一个 client唯一自增的id (request.getOpaque(); requestId.getAndIncrement())。
把id和上下文存储到请求待响应table中：发送请求后(写入channel)，线程等待结果响应 responseFuture.waitResponse，利用countDownLatch等待结果。
异步调用
发起请求
public void invokeAsyncImpl(final Channel channel, final RemotingCommand request, final long timeoutMillis,final InvokeCallback invokeCallback)// 唯一idfinal int opaque = request.getOpaque();... final ResponseFuture responseFuture = new ResponseFuture(channel, opaque, timeoutMillis - costTime, invokeCallback, once);// 把当前请求记录到待响应table中this.responseTable.put(opaque, responseFuture);...channel.writeAndFlush(request).addListener(new ChannelFutureListener() {@Overridepublic void operationComplete(ChannelFuture f) throws Exception {if (f.isSuccess()) {//标记为写入成功responseFuture.setSendRequestOK(true);return;}requestFail(opaque);log.warn("send a request command to channel <{}> failed.", RemotingHelper.parseChannelRemoteAddr(channel));}}); ...}关键设计点：每一个请求request，都分配了一个 client唯一自增的id (request.getOpaque(); requestId.getAndIncrement())。
把id和上下文存储到请求待响应table中：发送请求后，将callback传递给responseFuture，等待callback被调用。
单向调用oneway
发起请求
public void invokeOnewayImpl(final Channel channel, final RemotingCommand request, final long timeoutMillis)throws InterruptedException, RemotingTooMuchRequestException, RemotingTimeoutException, RemotingSendRequestException {request.markOnewayRPC();...boolean acquired = this.semaphoreOneway.tryAcquire(timeoutMillis, TimeUnit.MILLISECONDS);final SemaphoreReleaseOnlyOnce once = new SemaphoreReleaseOnlyOnce(this.semaphoreOneway);channel.writeAndFlush(request).addListener(new ChannelFutureListener() {@Overridepublic void operationComplete(ChannelFuture f) throws Exception {once.release();if (!f.isSuccess()) {log.warn("send a request command to channel <" + channel.remoteAddress() + "> failed.");}}});...}无需监听结果
关键设计点：使用信号量Semaphore控制并发数
是通道瞬间并发度，不同于流控qps
oneway模式：不同于同步调用 异步调用 这里不关心返回值 所以无需记录id到待响应table
▐ server受理请求 路由
监听请求
class NettyServerHandler extends SimpleChannelInboundHandler<RemotingCommand> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {processMessageReceived(ctx, msg);}}public void processMessageReceived(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {final RemotingCommand cmd = msg;if (cmd != null) {switch (cmd.getType()) {// 来自client的请求case REQUEST_COMMAND:processRequestCommand(ctx, cmd);break;// 来自client的响应case RESPONSE_COMMAND:processResponseCommand(ctx, cmd);break;default:break;}}}public void processRequestCommand(final ChannelHandlerContext ctx, final RemotingCommand cmd) {// 路由关系 线程池配置 查询 final Pair<NettyRequestProcessor, ExecutorService> matched = this.processorTable.get(cmd.getCode());final Pair<NettyRequestProcessor, ExecutorService> pair = null == matched ? this.defaultRequestProcessor : matched;final int opaque = cmd.getOpaque();...Runnable run = new Runnable() {@Overridepublic void run() {...final RemotingResponseCallback callback = new RemotingResponseCallback() {@Overridepublic void callback(RemotingCommand response) {... // 非oneway模式 才需要回写responseif (!cmd.isOnewayRPC()) {...ctx.writeAndFlush(response); ...}}};...// 使用指定的业务处理器processor处理业务NettyRequestProcessor processor = pair.getObject1();RemotingCommand response = processor.processRequest(ctx, cmd);callback.callback(response); ...}};...// 包装为线程任务 放到配置的线程池中执行final RequestTask requestTask = new RequestTask(run, ctx.channel(), cmd);pair.getObject2().submit(requestTask);...}关键设计点
抽象复用：
client 和 server的 网络通信读模块是高度一致的，所以抽象出来共有的部分，复用代码，继承结构：
是一个很标准的抽象复用案例, 但需注意在两个角色(client server)中同一份代码是有不一样的解读链路
路由实现：
利用code - processor - pool 的三者映射关系方便的拿到对应业务的处理器及其独立的线程池，进行任务投递
设计理念类似观察者模式，添加观察者-业务处理器(这里仅单个观察者)，当事件来了(socket消息读取)后，通知到所有观察者进行具体业务处理。
▐ client 监听响应
监听 同步调用结果
class NettyClientHandler extends SimpleChannelInboundHandler<RemotingCommand> { @Override protected void channelRead0(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {processMessageReceived(ctx, msg);}}public void processMessageReceived(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {final RemotingCommand cmd = msg;if (cmd != null) {switch (cmd.getType()) {// 来自server的请求case REQUEST_COMMAND:processRequestCommand(ctx, cmd);break;// 来自server的响应case RESPONSE_COMMAND:processResponseCommand(ctx, cmd);break;default:break;}}}public void processResponseCommand(ChannelHandlerContext ctx, RemotingCommand cmd) {final int opaque = cmd.getOpaque();// 从待响应table中找到响应对应的请求final ResponseFuture responseFuture = responseTable.get(opaque);if (responseFuture != null) {responseFuture.setResponseCommand(cmd);responseTable.remove(opaque);if (responseFuture.getInvokeCallback() != null) {// 异步调用 回调callbackexecuteInvokeCallback(responseFuture);} else {// 同步调用// 写入正常结果 并唤起wait的线程responseFuture.putResponse(cmd);public void putResponse(final RemotingCommand responseCommand) {this.responseCommand = responseCommand;this.countDownLatch.countDown();}responseFuture.release();}} else {log.warn("receive response, but not matched any request, " + RemotingHelper.parseChannelRemoteAddr(ctx.channel()));log.warn(cmd.toString());}}关键设计点
异步协调 && 同步等待 && 唤起机制
读取到来自server响应数据的线程 -> 通过待响应table查找当前响应归属的请求 -> 操作其countDownLatch定向唤起等待结果的请求线程
同步结果唤起条件：写入异常 || 等待超时 || 读取到来自server的对应id的响应
// 同步等待结果
RemotingCommand responseCommand = responseFuture.waitResponse(timeoutMillis);
监听 异步调用结果
class NettyClientHandler extends SimpleChannelInboundHandler<RemotingCommand> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {processMessageReceived(ctx, msg);}}public void processMessageReceived(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {final RemotingCommand cmd = msg;if (cmd != null) {switch (cmd.getType()) {// 来自server的请求case REQUEST_COMMAND:processRequestCommand(ctx, cmd);break;// 来自server的响应case RESPONSE_COMMAND:processResponseCommand(ctx, cmd);break;default:break;}}}public void processResponseCommand(ChannelHandlerContext ctx, RemotingCommand cmd) {final int opaque = cmd.getOpaque();// 从待响应table中找到响应对应的请求final ResponseFuture responseFuture = responseTable.get(opaque);if (responseFuture != null) {responseFuture.setResponseCommand(cmd);responseTable.remove(opaque);if (responseFuture.getInvokeCallback() != null) {// 异步调用executeInvokeCallback(responseFuture);} else {// 同步调用// 写入结果 并唤起wait的线程responseFuture.putResponse(cmd);public void putResponse(final RemotingCommand responseCommand) {this.responseCommand = responseCommand;this.countDownLatch.countDown();}responseFuture.release();}} else {log.warn("receive response, but not matched any request, " + RemotingHelper.parseChannelRemoteAddr(ctx.channel()));log.warn(cmd.toString());}}private void executeInvokeCallback(final ResponseFuture responseFuture) {ExecutorService executor = this.getCallbackExecutor();...executor.submit(new Runnable() {@Overridepublic void run() {try {responseFuture.executeInvokeCallback();} catch (Throwable e) {log.warn("execute callback in executor exception, and callback throw", e);} finally {responseFuture.release();}}});... }关键设计点
异步协调 && callback机制
读取到来自server响应数据的线程 -> 通过待响应table查找当前响应归属的请求 -> 回调callback
异步结果回调callback条件：写入异常 || 等待超时 || 读取到来自server的对应id的响应
另外callback执行采用了cas机制限制仅执行一次
模块升级-微服务化通信工具
why?
从业务视角开发来看，通信模块依然是比较基础的，对于普通开发者，希望能够像hsf一样，简单的定制协议service，契合java接口实现多态机制，不希望每次都去根据code或其他url之类的手动去分发路由，显得过于原始。
how?
参考hsf系列的远程调用方式，使用动态代理规范化协议传输，使用泛化反射机制便捷调用。
封装程度跟灵活程度往往是成反比的，注意不要过度设计，尽可能保留原始通信模块的灵活。
▐ 使用方式
定义接口 和 实现
public interface ServiceHello {String sayHello(String a, String b);Integer sayHelloInteger(Integer a, Integer b);
}import com.uext.remote.rf.service.ServiceHello;
public class ServiceHelloImpl implements ServiceHello {@Overridepublic String sayHello(String a, String b) {return "hello " + a + " " + b;}@Overridepublic Integer sayHelloInteger(Integer a, Integer b) {return 1000 + a + b;}
}同hsf，接口interface可打包后提供给消费者，实现类隐藏于提供者代码中
启动provider 注册服务监听
import com.alibaba.fastjson.JSON;
import com.uext.remote.rf.provider.ServiceHelloImpl;
import com.uext.remote.rf.provider.ServiceWorldImpl;
import com.uext.remote.rf.service.ServiceHello;
import com.uext.remote.rf.service.ServiceWorld;public class TestServer {public static void main(String[] args) throws Exception {ApiProviderBean apiProviderBean = new ApiProviderBean();apiProviderBean.setPort(8888);apiProviderBean.init();apiProviderBean.register(ServiceHello.class, new ServiceHelloImpl());apiProviderBean.register(ServiceWorld.class, new ServiceWorldImpl());System.out.println("start ok " + JSON.toJSONString(apiProviderBean));System.in.read();}
}启动服务端，注册一些需要暴露的服务，通过接口和接口的实现类的实例进行绑定
启动consumer 发起调用
import com.uext.remote.rf.service.ServiceHello;
import com.uext.remote.rf.service.ServiceWorld;
import org.apache.rocketmq.remoting.netty.NettyClientConfig;
import org.apache.rocketmq.remoting.netty.NettyRemotingClient;
public class TestClient {public static void main(String[] args) throws Exception {// 初始化一个连接客户端NettyClientConfig nettyServerConfig = new NettyClientConfig();NettyRemotingClient remotingClient = new NettyRemotingClient(nettyServerConfig, null);remotingClient.start();ApiConsumerBean apiConsumerBean = new ApiConsumerBean();apiConsumerBean.setRemotingClient(remotingClient);apiConsumerBean.setInterfac(ServiceHello.class);apiConsumerBean.setTimeOut(30000L);apiConsumerBean.setAddr("127.0.0.1:8888");ServiceHello serviceHello = apiConsumerBean.getProxy();ApiConsumerBean apiConsumerBean2 = new ApiConsumerBean();apiConsumerBean2.setRemotingClient(remotingClient);apiConsumerBean2.setInterfac(ServiceWorld.class);apiConsumerBean2.setTimeOut(30000L);apiConsumerBean2.setAddr("127.0.0.1:8888");ServiceWorld serviceWorld = apiConsumerBean2.getProxy();System.out.println(serviceHello.sayHello("a", "b"));System.out.println(serviceHello.sayHelloInteger(1, 2));serviceWorld.sayWorld("aa", "bb");System.in.read();}
}初始化一个长连接客户端, 获取接口远程实现实例, 发起调用。
日志输出
Connected to the target VM, address: '127.0.0.1:49830', transport: 'socket'
start ok {"index":{"com.uext.remote.hsf.service.ServiceWorld":{"public abstract void com.uext.remote.hsf.service.ServiceWorld.sayWorld(java.lang.String,java.lang.String)":{}},"com.uext.remote.hsf.service.ServiceHello":{"public abstract java.lang.Integer com.uext.remote.hsf.service.ServiceHello.sayHelloInteger(java.lang.Integer,java.lang.Integer)":{},"public abstract java.lang.String com.uext.remote.hsf.service.ServiceHello.sayHello(java.lang.String,java.lang.String)":{}}},"port":8888,"remotingServer":{"callbackExecutor":{"activeCount":0,"completedTaskCount":0,"corePoolSize":4,"largestPoolSize":0,"maximumPoolSize":4,"poolSize":0,"queue":[],"rejectedExecutionHandler":{},"shutdown":false,"taskCount":0,"terminated":false,"terminating":false,"threadFactory":{}},"rPCHooks":[]}}
world aa bbConnected to the target VM, address: '127.0.0.1:53211', transport: 'socket'
hello a b
1003▐ 实现方式
请求头 参数协议
import lombok.Data;
import org.apache.rocketmq.remoting.CommandCustomHeader;
import org.apache.rocketmq.remoting.exception.RemotingCommandException;
@Data
public class CommonHeader implements CommandCustomHeader{/*** com.uext.remote.hsf.service.ServiceHello*/String interfaceName;/*** public abstract java.lang.String com.uext.remote.hsf.service.ServiceHello.sayHello(java.lang.String,java.lang.String)*/String methodName;String argsJsonJson;@Overridepublic void checkFields() throws RemotingCommandException {}
}使用接口interface package url 和 方法 method的作为识别码，用以路由选择。
其中动态参数问题，需要考虑如何解决解码为方法参数对应的不同类型，本文采用简易实现(json)。
provider实现代码
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.TypeReference;
import io.netty.channel.ChannelHandlerContext;
import lombok.Data;
import org.apache.rocketmq.remoting.netty.*;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.util.*;
@Data
public class ApiProviderBean {private int port = 8888;// 长连接实例private NettyRemotingServer remotingServer;public void init() throws Exception {NettyServerConfig nettyServerConfig = new NettyServerConfig();nettyServerConfig.setListenPort(port);remotingServer = new NettyRemotingServer(nettyServerConfig, null);remotingServer.registerProcessor(0, new NettyRequestProcessor() {@Overridepublic RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws Exception {// 请求数据解析CommonHeader commonHeader = (CommonHeader) request.decodeCommandCustomHeader(CommonHeader.class);// 路由查找Map<String/*method*/, Call> map = index.get(commonHeader.getInterfaceName());Call call = Objects.requireNonNull(map, "interface not exists " + commonHeader.getInterfaceName()).get(commonHeader.getMethodName());if(call == null){throw new RuntimeException("method not exists " + commonHeader.getMethodName());}// 参数解码 todo 优化解码编码Parameter[] ts = call.method.getParameters();List<Object> args = new ArrayList<>();List<String> argsJson = JSON.parseObject(commonHeader.argsJsonJson, new TypeReference<List<String>>(){});for (int i = 0; i < argsJson.size(); i++) {// 根据method规范 逐一反序列化args.add(JSON.parseObject(argsJson.get(i), ts[i].getType()));}// 反射调用Object res = call.method.invoke(call.instance, args.toArray(new Object[0]));// 结果编码 回传 todo 优化解码编码RemotingCommand response = RemotingCommand.createResponseCommand(0, null);if(res != null) {response.setBody(JSON.toJSONBytes(res));}return response;}@Overridepublic boolean rejectRequest() {return false;}}, null);remotingServer.start();}private static class Call{Object instance;Method method;}private Map<String/*interface*/, Map<String/*method*/, Call>> index = new HashMap<>();/*** @param interfac 接口 协议* @param impl 实现类的实例*/public synchronized <T> void register(Class<T> interfac, T impl){// 建立 接口-实现类-方法 路由关系String iname = interfac.getName();Map<String/*method*/, Call> map = index.get(iname);if(map == null){map = new LinkedHashMap<>();index.put(iname, map);}for (Method declaredMethod : interfac.getDeclaredMethods()) {Call call = new Call();call.instance = impl;call.method = declaredMethod;map.put(declaredMethod.toString(), call);}}
}关键在于 注册协议(interface)和实现类, 维护映射路由关系。
收到channel请求的数据后，解码，根据映射路由关系进行反射调用拿到结果，编码结果，回写到channel
由于通道code 定义为int，但为了灵活配置接口及实现，不想硬编码，所以丢失了自定义不同业务线程池的特性，如果有需要可以重构通道code为string，然后把相关路由协议序列化到通道code中。
consumer实现代码
import com.alibaba.fastjson.JSON;
import lombok.Data;
import org.apache.rocketmq.remoting.netty.NettyRemotingClient;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
@Data
public class ApiConsumerBean implements InvocationHandler {/*** 超时时间*/private Long timeOut = 3000L;/*** 目标 ip:port*/private String addr = "127.0.0.1:8888";/*** 实现类*/private Class<?> interfac;/*** 长连接实例*/private NettyRemotingClient remotingClient;/*** 获取协议 代理实例*/public <T> T getProxy() throws IllegalArgumentException {return (T) Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class[]{interfac}, this);}/*** 规范编码协议*/@Overridepublic Object invoke(Object target, Method method, Object[] args) throws Throwable {if (Object.class.equals(method.getDeclaringClass())) {return method.invoke(this, args);}// 协议编码入参CommonHeader header = new CommonHeader();header.setInterfaceName(interfac.getName());header.setMethodName(method.toString());// todo 优化解码编码List<String> argJson = new ArrayList<>();for (Object arg : args) {argJson.add(JSON.toJSONString(arg));}header.setArgsJsonJson(JSON.toJSONString(argJson));// 定义通道code 0 为 远程使用RemotingCommand request = RemotingCommand.createRequestCommand(0, header);Object res = null;if(method.getReturnType() != null) {RemotingCommand response = remotingClient.invokeSync(addr, request, timeOut);// 协议解码结果 todo 优化解码编码if(response.getBody() != null && response.getBody().length > 0) {res = JSON.parseObject(new String(response.getBody(), StandardCharsets.UTF_8), method.getReturnType());}}else{remotingClient.invokeOneway(addr, request, timeOut);}return res;}
}关键在于 委托接口(interface)的调用实现, 动态代理为: 根据协议编码, 包装request之后写入channel
同步等待, 所以采用了同步调用模式
收到channel响应的结果后, 解码, 返回结果
其中无返回值的接口, 不关心响应结果, 可使用oneway方式调用
▐ 更进一步 注册中心 ip自动选择
引入注册中心 zk 或 namesrv，通过中心化协调，让某一些consumer自动选择某一台provider，并同时可以支持配置中心化下放，实现服务治理，越来越像微服务(dubbo)框架了哈。
当然，在跟多业务场景中，是无法引入其他中间件的，能少依赖就少依赖，降低复杂度。
在内网环境中，绝大部分项目采用Axxx一站式发布部署，配套Nxxxxxxx集群云资源管理，是支持按应用名动态获取当前集群ip清单的。
curl http://xxxxx.xxxx
{"num": 164,"result": [{"dns_ip": "13.23.xx.xxx", "state": "working_online"},...],"start": 0,"total": 164
}那么我们是否可以依赖该 ip清单，用来做本地hash ip自动选择呢？
当然可以，配合可用性心跳探测，每台机器节点自己维护一份可用性提供者消费者清单缓存，通过一致性hash等算法选择机器匹配机器。
那么就得到了一个简易版的低依赖，去中心化，高可用的微服务通信框架。
团队介绍
大淘宝技术开放平台，是淘宝天猫与外部生态互联互通的重要开放途径，通过开放的产品技术把一系列基础服务像水、电、煤一样输送给我们的商家、开发者、社区媒体以及其他合作伙伴，推动行业的定制、创新、进化，并最终促成新商业文明生态圈。
我们是一支技术能力雄厚，有着光荣历史传统的技术团队。在历年双十一战场上，团队都表现着优异的成绩。这里承载着每秒百万级的业务处理，90%的订单通过订单推送服务实时地推送到商家的ERP系统完成电商作业，通过奇门开放的ERP-WMS场景已经成为仓储行业标准。随着新零售业务的持续探索与快速发展，我们渴求各路高手加入，参与核心系统架构设计、性能调优，开放模式创新等富有技术挑战的工作。
¤ 拓展阅读 ¤
3DXR技术 | 终端技术 | 音视频技术
服务端技术 | 技术质量 | 数据算法
