企业级工作流解决方案（九）--微服务Tcp消息传输模型之客户端处理

客户端启动

　　客户端启动主要做三件事情，1. 从配置文件读取服务调用配置，存储到全局对象中。2. 指定客户端编解码器工厂。3. 预连接，即预先建立与服务端的通信Chanel。

[DependsOn(typeof(AbpKernelModule))]
    public class JsonRpcClientModule : AbpModule
    {
        public override void PreInitialize()
        {
            // 注册客户端配置，固定从Xml文件读取
            SocketClientConfiguration socketClientConfiguration = XmlConfigProvider.GetConfig<SocketClientConfiguration>("SocketClientConfiguration.xml");
            IocManager.IocContainer.Register(
                Component
                    .For<ISocketClientConfiguration>()
                    .Instance(socketClientConfiguration)
            );
            switch (socketClientConfiguration.MessageCode)
            {
                case EMessageCode.Json:
                    IocManager.RegisterIfNot<ITransportMessageCodecFactory, JsonTransportMessageCodecFactory>(Dependency.DependencyLifeStyle.Singleton);
                    break;
                case EMessageCode.MessagePack:
                    IocManager.RegisterIfNot<ITransportMessageCodecFactory, MessagePackTransportMessageCodecFactory>(Dependency.DependencyLifeStyle.Singleton);
                    break;
                case EMessageCode.ProtoBuffer:
                    IocManager.RegisterIfNot<ITransportMessageCodecFactory, ProtoBufferTransportMessageCodecFactory>(Dependency.DependencyLifeStyle.Singleton);
                    break;
            }
        }

        public override void Initialize()
        {
            IocManager.RegisterAssemblyByConvention(typeof(JsonRpcClientModule).GetAssembly());
            var dotNettyTransportClientFactory = new DotNettyTransportClientFactory(IocManager.Resolve<ITransportMessageCodecFactory>(), Logger);

            IocManager.IocContainer.Register(
                Component
                    .For<ITransportClientFactory>()
                    .Instance(dotNettyTransportClientFactory)
            );
        }

        public override void PostInitialize()
        {
            var socketClientConfiguration = Configuration.Modules.RpcClientConfig();
            var transportClientFactory = IocManager.Resolve<ITransportClientFactory>();
            try
            {
                foreach (var clientConnectServerInfo in socketClientConfiguration.ClientConnectServerInfos) // 预连接
                {
                    if (clientConnectServerInfo.ConnectServerType == EConnectServerType.Tcp)
                    {
                        var tcpAddress = clientConnectServerInfo.Url.Split(new char[] { ':' }, StringSplitOptions.RemoveEmptyEntries);
                        transportClientFactory.CreateClient(new IpAddressModel(tcpAddress[0], int.Parse(tcpAddress[1])).CreateEndPoint());
                    }
                }
            }
            catch(Exception ex) // 预连，出错不处理
            {

            }
        }
    }

客户端全局Chanel设计

　　每一个服务连接创建一个TransportClient与之对应，存储在全局变量中private readonly ConcurrentDictionary<EndPoint, Lazy<ITransportClient>> _clients = new ConcurrentDictionary<EndPoint, Lazy<ITransportClient>>();

　　TransportClient即处理客户端传输消息对象，每当发起客户端调用时，创建transportClient对象，并存储到_clients集合中，下次对同一个服务端调用时，直接复用此对象，如果与服务器的通信Chanel断开，则从_clients对象中移除，达到了复用Chanel的作用。

/// <summary>
        /// 创建客户端。
        /// </summary>
        /// <param name="endPoint">终结点。</param>
        /// <returns>传输客户端实例。</returns>
        public ITransportClient CreateClient(EndPoint endPoint)
        {
            var key = endPoint;
            _logger.Debug($"准备为服务端地址：{key}创建客户端。");
            try
            {
                return _clients.GetOrAdd(key
                    , k => new Lazy<ITransportClient>(() =>
                    {
                        var bootstrap = _bootstrap;
                        var channel = bootstrap.ConnectAsync(k).Result;
                        var messageListener = new MessageListener();
                        channel.GetAttribute(messageListenerKey).Set(messageListener);
                        var messageSender = new DotNettyMessageClientSender(_transportMessageEncoder, channel);
                        channel.GetAttribute(messageSenderKey).Set(messageSender);
                        channel.GetAttribute(origEndPointKey).Set(k);
                        var client = new TransportClient(messageSender, messageListener, _logger);
                        return client;
                    }
                    )).Value;
            }
            catch
            {
                _clients.TryRemove(key, out var value);
                var ipEndPoint = endPoint as IPEndPoint;
                throw;
            }
        }
protected class DefaultChannelHandler : ChannelHandlerAdapter
        {

            public override void ChannelInactive(IChannelHandlerContext context)
            {
                _factory._clients.TryRemove(context.Channel.GetAttribute(origEndPointKey).Get(), out var value);
            }
        }

TransportClient

　　默认的客户端传输实现，Rpc调用时，直接组装请求参数，调用SendAsync方法。注意里面的ManualResetValueTaskSource的设计。

/// <summary>
    /// 一个默认的传输客户端实现。
    /// </summary>
    public class TransportClient : ITransportClient, IDisposable
    {
        #region Field

        private readonly IMessageSender _messageSender;
        private readonly IMessageListener _messageListener;
        private readonly ILogger _logger;

        private readonly ConcurrentDictionary<string, ManualResetValueTaskSource<TransportMessage>> _resultDictionary =
            new ConcurrentDictionary<string, ManualResetValueTaskSource<TransportMessage>>();

        #endregion Field

        #region Constructor

        public TransportClient(IMessageSender messageSender, IMessageListener messageListener, ILogger logger)
        {
            _messageSender = messageSender;
            _messageListener = messageListener;
            _logger = logger;
            messageListener.Received += MessageListener_Received;
        }

        #endregion Constructor

        #region Implementation of ITransportClient

        /// <summary>
        /// 发送消息。
        /// </summary>
        /// <param name="message">远程调用消息模型。</param>
        /// <returns>远程调用消息的传输消息。</returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public async Task<JsonResponse> SendAsync(JsonRequest message, NameValueCollection contextNameValueCollection, CancellationToken cancellationToken)
        {
            try
            {
                _logger.Debug("准备发送消息。");

                var transportMessage = TransportMessage.CreateInvokeMessage(message, contextNameValueCollection);

                //注册结果回调
                var callbackTask = RegisterResultCallbackAsync(transportMessage.Id, cancellationToken);

                try
                {
                    //发送
                    await _messageSender.SendAndFlushAsync(transportMessage);
                }
                catch (Exception exception)
                {
                    throw new CommunicationException("与服务端通讯时发生了异常。", exception);
                }

                _logger.Debug("消息发送成功。");

                return await callbackTask;
            }
            catch (Exception exception)
            {
                _logger.Error("消息发送失败。");
                throw;
            }
        }

        #endregion Implementation of ITransportClient

        #region Implementation of IDisposable

        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
        public void Dispose()
        {
            (_messageSender as IDisposable)?.Dispose();
            (_messageListener as IDisposable)?.Dispose();
            foreach (var taskCompletionSource in _resultDictionary.Values)
            {
                taskCompletionSource.SetCanceled();
            }
        }

        #endregion Implementation of IDisposable

        #region Private Method

        /// <summary>
        /// 注册指定消息的回调任务。
        /// </summary>
        /// <param name="id">消息Id。</param>
        /// <returns>远程调用结果消息模型。</returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private async Task<JsonResponse> RegisterResultCallbackAsync(string id, CancellationToken cancellationToken)
        {
            _logger.Debug($"准备获取Id为：{id}的响应内容。");

            var task = new ManualResetValueTaskSource<TransportMessage>();
            _resultDictionary.TryAdd(id, task);
            try
            {
                var result = await task.AwaitValue(cancellationToken);
                return result.GetContent<JsonResponse>();
            }
            finally
            {
                //删除回调任务
                ManualResetValueTaskSource<TransportMessage> value;
                _resultDictionary.TryRemove(id, out value);
                value.SetCanceled();
            }
        }

        private async Task MessageListener_Received(IMessageSender sender, TransportMessage message)
        {
            _logger.Debug("服务消费者接收到消息。");

            ManualResetValueTaskSource<TransportMessage> task;
            if (!_resultDictionary.TryGetValue(message.Id, out task))
                return;

            if (message.IsInvokeResultMessage())
            {
                var content = message.GetContent<JsonResponse>();
                if (content.Error != null)
                {
                    task.SetException(content.Error);
                }
                else
                {
                    task.SetResult(message);
                }
            }
        }

        #endregion Private Method
    }