第十七节：CAP框架5.x版本新特性和CAP框架源码剖析
一. CAP5.X 新特性
(参考官方博客：https://www.cnblogs.com/savorboard/p/cap-5-0.html)
1. 适配 .NET 5 和 .NET Standard 2.1
2. 增加了对 NATS Transport 的支持
NATS 是一个简单，安全，高性能的开源消息传递系统，适用于云原生应用，IoT消息传递和微服务架构，目前也是 CNCF 下的一个项目。
services.AddCap(x => { ... x.UseNATS(""); });
3. 替换 Newtonsoft.Json 为 System.Text.Json
4. RabbitMq中变化
(1). 启用消息确认机制
(2). 支持创建 lazy 队列的选项
RabbitMQ 在 3.1.6 引入了 lazy queue的概念，用于将消息尽早的转移到磁盘，然后在消费的时候才加载到 RAM 中。
具体可以查看这里的介绍： https://www.rabbitmq.com/lazy-queues.html
集成方式：
services.AddCap(x => { ... x.UseRabbitMQ(aa => { ... aa.QueueArguments.QueueMode = "lazy"; }); }
5. Kafka中变化
6. 添加自定义 Group 和 Topic 前缀的选项
在一些场景中需要对Group或者Topic 进行区分，特别是AWS SQS由于不同项目都是使用的同一个云服务来共享SNS和SQS，所以这种情况下进行添加前缀就更加直观的看出来。
在本版本中，我们支持了自定义对Group和Topic的前缀添加功能
7. 修改bug
二. CAP框架源码剖析
1. 发布环节
// Copyright (c) .NET Core Community. All rights reserved. // Licensed under the MIT License. See License.txt in the project root for license information. using System; using System.Collections.Generic; using System.Diagnostics; using System.Threading; using System.Threading.Tasks; using DotNetCore.CAP.Diagnostics; using DotNetCore.CAP.Messages; using DotNetCore.CAP.Persistence; using DotNetCore.CAP.Transport; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Options; namespace DotNetCore.CAP.Internal { internal class CapPublisher : ICapPublisher { private readonly IDispatcher _dispatcher; private readonly IDataStorage _storage; private readonly CapOptions _capOptions; // ReSharper disable once InconsistentNaming protected static readonly DiagnosticListener s_diagnosticListener = new DiagnosticListener(CapDiagnosticListenerNames.DiagnosticListenerName); public CapPublisher(IServiceProvider service) { ServiceProvider = service; _dispatcher = service.GetRequiredService<IDispatcher>(); _storage = service.GetRequiredService<IDataStorage>(); _capOptions = service.GetService<IOptions<CapOptions>>().Value; Transaction = new AsyncLocal<ICapTransaction>(); } public IServiceProvider ServiceProvider { get; } public AsyncLocal<ICapTransaction> Transaction { get; } public Task PublishAsync<T>(string name, T value, IDictionary<string, string> headers, CancellationToken cancellationToken = default) { return Task.Run(() => Publish(name, value, headers), cancellationToken); } public Task PublishAsync<T>(string name, T value, string callbackName = null, CancellationToken cancellationToken = default) { return Task.Run(() => Publish(name, value, callbackName), cancellationToken); } public void Publish<T>(string name, T value, string callbackName = null) { var header = new Dictionary<string, string> { {Headers.CallbackName, callbackName} }; Publish(name, value, header); } public void Publish<T>(string name, T value, IDictionary<string, string> headers) { if (string.IsNullOrEmpty(name)) { throw new ArgumentNullException(nameof(name)); } if (!string.IsNullOrEmpty(_capOptions.TopicNamePrefix)) { name = $"{_capOptions.TopicNamePrefix}.{name}"; } headers ??= new Dictionary<string, string>(); if (!headers.ContainsKey(Headers.MessageId)) { var messageId = SnowflakeId.Default().NextId().ToString(); headers.Add(Headers.MessageId, messageId); } if (!headers.ContainsKey(Headers.CorrelationId)) { headers.Add(Headers.CorrelationId, headers[Headers.MessageId]); headers.Add(Headers.CorrelationSequence, 0.ToString()); } headers.Add(Headers.MessageName, name); headers.Add(Headers.Type, typeof(T).Name); headers.Add(Headers.SentTime, DateTimeOffset.Now.ToString()); var message = new Message(headers, value); long? tracingTimestamp = null; try { tracingTimestamp = TracingBefore(message); if (Transaction.Value?.DbTransaction == null) { var mediumMessage = _storage.StoreMessage(name, message); TracingAfter(tracingTimestamp, message); _dispatcher.EnqueueToPublish(mediumMessage); } else { var transaction = (CapTransactionBase)Transaction.Value; var mediumMessage = _storage.StoreMessage(name, message, transaction.DbTransaction); TracingAfter(tracingTimestamp, message); transaction.AddToSent(mediumMessage); if (transaction.AutoCommit) { transaction.Commit(); } } } catch (Exception e) { TracingError(tracingTimestamp, message, e); throw; } } #region tracing private long? TracingBefore(Message message) { if (s_diagnosticListener.IsEnabled(CapDiagnosticListenerNames.BeforePublishMessageStore)) { var eventData = new CapEventDataPubStore() { OperationTimestamp = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(), Operation = message.GetName(), Message = message }; s_diagnosticListener.Write(CapDiagnosticListenerNames.BeforePublishMessageStore, eventData); return eventData.OperationTimestamp; } return null; } private void TracingAfter(long? tracingTimestamp, Message message) { if (tracingTimestamp != null && s_diagnosticListener.IsEnabled(CapDiagnosticListenerNames.AfterPublishMessageStore)) { var now = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(); var eventData = new CapEventDataPubStore() { OperationTimestamp = now, Operation = message.GetName(), Message = message, ElapsedTimeMs = now - tracingTimestamp.Value }; s_diagnosticListener.Write(CapDiagnosticListenerNames.AfterPublishMessageStore, eventData); } } private void TracingError(long? tracingTimestamp, Message message, Exception ex) { if (tracingTimestamp != null && s_diagnosticListener.IsEnabled(CapDiagnosticListenerNames.ErrorPublishMessageStore)) { var now = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(); var eventData = new CapEventDataPubStore() { OperationTimestamp = now, Operation = message.GetName(), Message = message, ElapsedTimeMs = now - tracingTimestamp.Value, Exception = ex }; s_diagnosticListener.Write(CapDiagnosticListenerNames.ErrorPublishMessageStore, eventData); } } #endregion } }
2. 监视环节
监听环节CapSubscribeAttribute---MethodMatcherCache缓存标记特性的方法---IConsumerServiceSelector查找---ConsumerServiceSelector---FindConsumersFromInterfaceTypes(ICapSubscribe)—FindConsumersFromControllerTypes(类以Controller)---把全部注册就都找到
了
ISubscribeInvoker—SubscribeInvoker---InvokeAsync---把方法组装成一个表达式目录树然后编译成一个委托，可以复用
3.定时任务
定时环节 AddCap---各种注册各种注册--- Bootstrapper---BootstrapAsync --- Storage.InitializeAsync初始化数据结构–BootstrapCoreAsync—启动全部的Processors---CapProcessingServer—start开启循环 pluse 未实现 dispose通过cts取消
Dispatcher---ctor---启动线程循环等待
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- 作 者 : Yaopengfei(姚鹏飞)
- 博客地址 : http://www.cnblogs.com/yaopengfei/
- 声 明1 : 如有错误，欢迎讨论，请勿谩骂^_^。
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