分布式事务DotNet Core.CAP（1）

在分布式系统中，存在分布式事务的问题需要我们去解决，这是一个不可避免的问题，.Net中有一个开源的分布式框架可以供我们使用。我们先来看看它是如何使用的。

1-新建一个.Net Core3.1的WebApi项目

2-引入以下包

3-新建一个WebApi作为消息队列的发布方

PublishController

[Route("api/[controller]")]
    [ApiController]
    public class PublishController : ControllerBase
    {
        private readonly string ConnectionString = MyConst.mysqlCommectionString;//数据库连接地址
        private readonly ICapPublisher _capBus;

        public PublishController(ICapPublisher capPublisher)
        {
            _capBus = capPublisher;

        }

        [Route("adonet/transaction/publish")]
        public IActionResult AdonetWithTransaction()
        {
            using (var connection = new MySqlConnection(ConnectionString))
            {
                using (var transaction = connection.BeginTransaction(_capBus, autoCommit: true))
                {
                    //your business logic code
                    _capBus.Publish("product.services.time", DateTime.Now);//product.services.time为消息队列的名称
                }
            }

            return Ok();

        }
    }

4-新建消息的订阅方

具体代码如下

public interface ISubscriberService
    {
        void ReceivedMessage(DateTime datetime);
    }


 public class SubscriberService : ISubscriberService, ICapSubscribe
    {
        [CapSubscribe("product.services.time")]
        public void ReceivedMessage(DateTime datetime)
        {
            Console.WriteLine($"============{datetime}===========");
            //throw new Exception($"异常重试!");

        }

    }

5-Startup.cs里面初始化DotNetCore.CAP框架内容

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            services.AddTransient<ISubscriberService, SubscriberService>();

            services.AddCap(x =>
            {
                x.UseMySql(MyConst.mysqlCommectionString);

                x.UseRabbitMQ(options =>
                {

                    options.UserName = "admin";//用户名

                    options.Password = "admin";//密码

                    options.HostName = "172.17.17.17";//rabbitmq ip

                    //options.Port = 15672;

                });

                x.UseDashboard();//DotNetCore.CAP框架管控台，地址是:http://localhost:端口/cap

            });

        }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();

            });

        }

    }

6-在数据库里面新建一个空的数据库，名字叫capdb,注意这个名字是可以自定义的，但注意在数据库连接地址的地址就要与你自定义的名字保持一致

7-我们请求地址

http://localhost:49237/api/Publish/adonet/transaction

8-这时订阅方即SubscriberService会收到消息

9-这时数据库里面会自动生成2张表，且里面会各自有一条数据，这表的作用可以认为就是分布式事务的事务日志表

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