1. 三种发送请求

在DubboInvoker的doInvoke中调用

三种调用方式

1. 同步
2. 异步返回
3. 异步不返回

之前已经介绍过ExchangeClient，可参考dubbo笔记-remoting(5)Exchanger

    protected Result doInvoke(final Invocation invocation) throws Throwable {
        RpcInvocation inv = (RpcInvocation) invocation;
        final String methodName = RpcUtils.getMethodName(invocation);
        inv.setAttachment(Constants.PATH_KEY, getUrl().getPath());
        inv.setAttachment(Constants.VERSION_KEY, version);

        ExchangeClient currentClient;
        if (clients.length == 1) {
            currentClient = clients[0];
        } else {
            currentClient = clients[index.getAndIncrement() % clients.length];
        }
        try {
            boolean isAsync = RpcUtils.isAsync(getUrl(), invocation);
            boolean isOneway = RpcUtils.isOneway(getUrl(), invocation);
            int timeout = getUrl().getMethodParameter(methodName, Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT);
            if (isOneway) {
                boolean isSent = getUrl().getMethodParameter(methodName, Constants.SENT_KEY, false);
                currentClient.send(inv, isSent);
                RpcContext.getContext().setFuture(null);
                return new RpcResult();
            } else if (isAsync) {
                ResponseFuture future = currentClient.request(inv, timeout);
                RpcContext.getContext().setFuture(new FutureAdapter<Object>(future));
                return new RpcResult();
            } else {
                RpcContext.getContext().setFuture(null);
                return (Result) currentClient.request(inv, timeout).get();
            }
        } catch (TimeoutException e) {
            throw new RpcException(RpcException.TIMEOUT_EXCEPTION, "Invoke remote method timeout. method: " + invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
        } catch (RemotingException e) {
            throw new RpcException(RpcException.NETWORK_EXCEPTION, "Failed to invoke remote method: " + invocation.getMethodName() + ", provider: " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }

参考:
Dubbo源码分析----发起请求

2. DefaultFuture

同步请求和异步返回内部实现实质是一样的，都是返回一个DefaultFuture,同步请求会调用DefaultFuture的get方法,阻塞等待线程结果返回,异步返回则将DefaultFuture返回给调用者,择机调用get方法
参考:Dubbo源码分析----DefaultFuture

3.接收请求

NettyServerHandler在接收到请求后会将请求转发到AllChannelHandler

AllChannelHandler会将请求在线程池中处理，ChannelEventRunnable是入口处理逻辑,最终会调用DubboProtocol的Invoker来调用方法执行

参考:
Dubbo源码分析----处理请求

4. Dispatcher

事件派发策略,上面的接收请求的AllChannelHandler就是接收事件派发策略的其中一种,即接收到请求都转到线程池中处理,还有其他处理方法
参考:Dubbo源码分析----Dispatcher和ThreadPool

4.请求超时处理

DefaultFuture静态构造函数里面会启动一个线程不断检查超时的请求处理

参考:
https://blog.csdn.net/lz710117239/article/details/77530536