13.分布式事件总线DotNetCore.CAP的简单使用

DotNetCore.CAP框架提供了一个简单易用的API和多种消息传输协议支持（包括Redis、RabbitMQ等），可以让用户轻松地实现消息队列、事件发布/订阅、分布式事务等功能。它还具备自动重试、异常处理、数据序列化等高级特性，可以保证消息的可靠性和一致性。

使用DotNetCore.CAP框架，你可以：

1. 发布并订阅消息，支持同步和异步模式；

2. 实现分布式事务管理，确保各个步骤的一致性；

3. 建立多种消息传输协议，如Kafka、RabbitMQ等；

4. 支持多种数据库驱动程序，如MySql、Oracle等；

5. 灵活采用自定义消息格式，以满足你的需求。

除此之外，该框架还具有良好的可扩展性，支持在集群环境下进行部署，并与其他.NET Core框架（如Entity Framework Core）完美配合使用。

 

安装包：

DotNetCore.CAP

DotNetCore.CAP.Dashboard

DotNetCore.CAP.MySql

DotNetCore.CAP.RabbitMQ

Microsoft.AspNetCore.OpenApi

Newtonsoft.Json

Pomelo.EntityFrameworkCore.MySql

Swashbuckle.AspNetCore

 

添加一个项目EventBus.DotnetCap(http://localhost:5284)

 

appsettings.Development.json配置

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "RabbitMQ": {
    "HostName": "127.0.0.1",
    "VirtualHost": "/",
    "UserName": "admin",
    "Password": "你的密码",
    "Port": "5672"
  },
  "ConnectionStrings": {
    "mysql": "server=127.0.0.1;uid=root;pwd=123456;database=DotnetCoreCap"
  }
}

安装RabbitMQ

1. 下载带web管理客户端的镜像：

docker pull rabbitmq:management

2. 创建容器并运行（15672是管理界面的端口，5672是服务的端口。这里顺便将管理系统的用户名和密码设置为admin admin）

docker run -d --name=rabbit --net=happy_travel --restart=always -e
RABBITMQ_DEFAULT_USER=admin -e RABBITMQ_DEFAULT_PASS=123456 -p 15672:15672 -p
5672:5672 rabbitmq:management

3. 若未设置,RABBITMQ_DEFAULT_USER,RABBITMQ_DEFAULT_PASS 时，默认账号密码都为:admin

4. 打开浏览器，输入网址：http://localhost:15672 ，输入账号与密码即可登录rabbitmq 客户端管理界面

 

添加一个EF链接Mysql的上下文MyDbContextContext.cs

public class MyDbContextContext:DbContext
{
    public MyDbContextContext(DbContextOptions<MyDbContextContext> options) : base(options)
    {
        
    }

    public DbSet<UserInfo> UserInfo { get; set; }
}

 

Program.cs配置

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();
builder.Services.AddSwaggerGen();
builder.Services.AddDbContext<MyDbContextContext>(p =>
{
    p.UseMySql(builder.Configuration.GetConnectionString("mysql"),new MySqlServerVersion("5.7"));
});
builder.Services.AddTransient<ReceiveService>();


// 配置事件总线以及分布式事务
var rabbitConfig = builder.Configuration.GetSection("RabbitMQ");
builder.Services.Configure<RabbitMQOptions>(rabbitConfig);
var rabbitOptions = rabbitConfig.Get<RabbitMQOptions>();

builder.Services.AddCap(p =>
{
    // 在数据库中会生成cap.receive 与 cap.publish 表
    // 同时也支持分布式事务
    p.UseMySql(builder.Configuration.GetConnectionString("mysql") ?? string.Empty);
    p.UseEntityFramework<MyDbContextContext>();
    p.UseRabbitMQ(mq =>
    {
        mq.HostName = rabbitOptions.HostName;
        mq.VirtualHost = rabbitOptions.VirtualHost;
        mq.UserName = rabbitOptions.UserName;
        mq.Password = rabbitOptions.Password;
        mq.Port = rabbitOptions.Port;
    });
     p.UseDashboard(); // 注册仪表盘
    // 仪表盘默认的访问地址是：http://localhost:xxx/cap，你可以在d.MatchPath配置项中修改cap路径后缀为其他的名字。
    //设置处理成功的数据在数据库中保存的时间（秒），为保证系统新能，数据会定期清理。
    p.SucceedMessageExpiredAfter = 24 * 3600;

    //设置失败重试次数
    p.FailedRetryCount = 5;
});


var app = builder.Build();


if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

 

添加一个控制器HomeController( 发布 )

[Route("[controller]/[action]")]
[ApiController]
public class HomeController:ControllerBase
{
    private readonly ICapPublisher _capPublisher;


    public HomeController(ICapPublisher capPublisher)
    {
        _capPublisher = capPublisher;
    }

    [HttpGet]
    public IActionResult TestPub()
    {
        _capPublisher.Publish("eventbus_Key01",new UserInfo{Id = 1,NickName = "张三"});
        return Ok("消息发布成功，请等待处理结果");
    }
    
    //在EventBus.DotnetCoreCap.Subscribe项目中接收
    [HttpGet]
    public IActionResult TestSubOnOtherProject()
    {
        _capPublisher.Publish("eventbus_Key02",new UserInfo{Id = 2,NickName = "李四"});
        return Ok("消息发布成功，请等待处理结果");
    }
}

 

添加一个控制器ReceiveController( 接收、订阅 )

[Route("[controller]/[action]")]
[ApiController]
public class ReceiveController:ControllerBase
{
    [NonAction]
    [CapSubscribe("eventbus_Key01",Group = "eventbus_Key01")]
    public void CheckReceive(UserInfo info)
    {
        var json = JsonConvert.SerializeObject(info);
        Console.WriteLine(json);
    }
}

或者

public class ReceiveService:ICapSubscribe
{
    [CapSubscribe("eventbus_Key01",Group = "eventbus_Key01")]
    public void CheckReceive(UserInfo info)
    {
        var json = JsonConvert.SerializeObject(info);
        Console.WriteLine(json);
    }
}

 

事务：

[Route("[controller]/[action]")]
[ApiController]
public class TransactionController:ControllerBase
{
    private readonly ICapPublisher _cap;
    private readonly MyDbContextContext _context;

    public TransactionController(ICapPublisher cap, MyDbContextContext context)
    {
        _cap = cap;
        _context = context;
    }
    // 原理：拆分成多个本地事务来看待
    // 场景1：正常事务消息发布
    [HttpGet]
    public IActionResult Publish1()
    {
        var tran = _context.Database.BeginTransaction(_cap);
        try
        {
            _context.UserInfo.Add(new() {NickName = "张三"});
            _context.SaveChanges();
            
            _cap.Publish("tran.cap","李四");
            
            tran.Commit();
            return Ok("成功");
        }
        catch (Exception e)
        {
            tran.Rollback();
            return Ok("失败");
        }
    }
    
    
    // 场景2：发布者发生异常, 消费者根本就收不到消息
    [HttpGet]
    public IActionResult Publish2()
    {
        var tran = _context.Database.BeginTransaction(_cap);
        try
        {
            _context.UserInfo.Add(new() {NickName = "张三2"});
            _context.SaveChanges();
            
            _cap.Publish("tran.cap2","李四2");
            throw new Exception("测试发布者出异常");
            
            tran.Commit();
            return Ok("成功");
        }
        catch (Exception e)
        {
            tran.Rollback();
            return Ok("失败");
        }
    }
    
    
    // 场景3： 发布者正常，消费者发生异常，不会导致发布者回滚
    [HttpGet]
    public IActionResult Publish3()
    {
        var tran = _context.Database.BeginTransaction(_cap);
        try
        {
            _context.UserInfo.Add(new() {NickName = "张三3"});
            _context.SaveChanges();
            
            _cap.Publish("tran.cap3","李四3");
            
            tran.Commit();
            return Ok("成功");
        }
        catch (Exception e)
        {
            tran.Rollback();
            return Ok("失败");
        }
    }
}

 

添加另一个项目EventBus.DotnetCoreCap.Subscribe(http://localhost:5187)

appsettings.Development.json配置

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "RabbitMQ": {
    "HostName": "127.0.0.1",
    "VirtualHost": "/",
    "UserName": "admin",
    "Password": "你的密码",
    "Port": "5672"
  },
  "ConnectionStrings": {
    "mysql": "server=127.0.0.1;uid=root;pwd=123456;database=DotnetCoreCap"
  }
}

public class MyDbContextContext:DbContext
{
    public MyDbContextContext(DbContextOptions<MyDbContextContext> options) : base(options)
    {
        
    }

    public DbSet<UserInfo> UserInfo { get; set; }
}

Program.cs配置

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.AddSwaggerGen();
builder.Services.AddDbContext<MyDbContextContext>(p =>
{
    p.UseMySql(builder.Configuration.GetConnectionString("mysql"),new MySqlServerVersion("5.7"));
});

var rabbitConfig = builder.Configuration.GetSection("RabbitMQ");
builder.Services.Configure<RabbitMQOptions>(rabbitConfig);
var rabbitOptions = rabbitConfig.Get<RabbitMQOptions>();

builder.Services.AddCap(p =>
{
    // 在数据库中会生成cap.receive 与 cap.publish 表
    p.UseMySql(builder.Configuration.GetConnectionString("mysql") ?? string.Empty);
    //p.UseEntityFramework<MyDbContextContext>();
    p.UseRabbitMQ(mq =>
    {
        mq.HostName = rabbitOptions.HostName;
        mq.VirtualHost = rabbitOptions.VirtualHost;
        mq.UserName = rabbitOptions.UserName;
        mq.Password = rabbitOptions.Password;
        mq.Port = rabbitOptions.Port;
    });
     p.UseDashboard(); // 注册仪表盘
    // 仪表盘默认的访问地址是：http://localhost:xxx/cap，你可以在d.MatchPath配置项中修改cap路径后缀为其他的名字。
    //设置处理成功的数据在数据库中保存的时间（秒），为保证系统新能，数据会定期清理。
    p.SucceedMessageExpiredAfter = 24 * 3600;

    //设置失败重试次数
    p.FailedRetryCount = 5;
});

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

添加一个控制器SubController用于订阅和接收

[Route("[controller]/[action]")]
[ApiController]
public class SubController:ControllerBase
{
    [NonAction]
    [CapSubscribe("eventbus_Key02",Group = "eventbus_Key02")]
    public void Receive(UserInfo info)
    {
        var json = JsonConvert.SerializeObject(info);
        Console.WriteLine(json);
    }
    
    
    [NonAction]
    [CapSubscribe("tran.cap",Group = "tran.cap")]
    public void ReceiveTran1(string nickName)
    {
        Console.WriteLine(nickName);
    }
    
    [NonAction]
    [CapSubscribe("tran.cap2",Group = "tran.cap2")]
    public void ReceiveTran2(string nickName)
    {
        Console.WriteLine(nickName);
    }
    
    [NonAction]
    [CapSubscribe("tran.cap3",Group = "tran.cap3")]
    public void ReceiveTran3(string nickName)
    {
        Console.WriteLine(nickName);
        // throw new Exception("消费者异常");
    }
}