RPC-BDY(5)-服务自动注销、负载均衡

RPC-BDY(5)

-2022.7.22

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一、负载均衡

1.loadBalancer接口

public interface LoadBalancer {
    
    Instance select(List<Instance> instances);
}

2.RandomLoadBalancer

public class RandomLoadBalancer implements LoadBalancer {
    

    @Override
    public Instance select(List<Instance> instances) {
    
        return instances.get(new Random().nextInt(instances.size()));
    }

}

3.在NacosServiceRegistry的lookupService中使用随机负载均衡

public InetSocketAddress lookupService(String serviceName) {
    
        try {
    
            List<Instance> instances = NacosUtil.getAllInstance(serviceName);
            Instance instance = loadBalancer.select(instances);
            return new InetSocketAddress(instance.getIp(), instance.getPort());
        } catch (NacosException e) {
    
            logger.error("获取服务时有错误发生:", e);
        }
        return null;
    }

二、服务自动注销

思路，在关闭服务线程时，使用钩子函数，这个钩子函数会在 JVM 关闭之前被调用

1.在NacosUtils类中写入clearRegistry方法

    public static void clearRegistry() {
    
        if(!serviceNames.isEmpty() && address != null) {
    
            String host = address.getHostName();
            int port = address.getPort();
            Iterator<String> iterator = serviceNames.iterator();
            while(iterator.hasNext()) {
    
                String serviceName = iterator.next();
                try {
    
                    namingService.deregisterInstance(serviceName, host, port);
                } catch (NacosException e) {
    
                    logger.error("注销服务 {} 失败", serviceName, e);
                }
            }
        }
    }

2.新建ShutdownHook钩子类

public class ShutdownHook {
    

    private static final Logger logger = LoggerFactory.getLogger(ShutdownHook.class);

    private final ExecutorService threadPool = ThreadPoolFactory.createDefaultThreadPool("shutdown-hook");
    private static final ShutdownHook shutdownHook = new ShutdownHook();

    public static ShutdownHook getShutdownHook() {
    
        return shutdownHook;
    }

    public void addClearAllHook() {
    
        logger.info("关闭后将自动注销所有服务");
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
    
            NacosUtil.clearRegistry();
            threadPool.shutdown();
        }));
    }

}

3.在 RpcServer 启动之前，只需要调用 addClearAllHook，就可以注册这个钩子了

             ChannelFuture future = serverBootstrap.bind(host, port).sync();
            ShutdownHook.getShutdownHook().addClearAllHook();
             future.channel().closeFuture().sync();

三、知识

钩子函数

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总结

从开始的RPC协议写起
有客户端，服务端
然后使用TCP传输
改用Netty的NIO进行
其中学序列化，编码不会