CAP 　　　　　　　　　　　　　　　　　　　　　　中文

CAP is a .Net Standard library to achieve eventually consistent in distributed architectures system like SOA,MicroService. It is lightweight,easy to use and efficiently.

OverView

CAP is a library that used in an ASP.NET Core project, Of Course you can ues it in ASP.NET Core with .NET Framework.

You can think of CAP as an EventBus because it has all the features of EventBus, and CAP provides a easier way to handle the publishing and subscribing than EventBus.

CAP has the function of Message Persistence, and it makes messages reliability when your service is restarted or down. CAP provides a Publish Service based on Microsoft DI that integrates seamlessly with your business services and supports strong consistency transactions.

This is a diagram of the CAP working in the ASP.NET Core MicroService architecture:

The solid line in the figure represents the user code, and the dotted line represents the internal implementation of the CAP.

Getting Started

NuGet

You can run the following command to install the CAP in your project.

PM> Install-Package DotNetCore.CAP

If your Message Queue is using Kafka, you can：

PM> Install-Package DotNetCore.CAP.Kafka

If your Message Queue is using RabbitMQ, you can：

PM> Install-Package DotNetCore.CAP.RabbitMQ

CAP supported SqlServer, MySql, PostgreSql as message store extension：

//Select a database provider you are using
PM> Install-Package DotNetCore.CAP.SqlServer
PM> Install-Package DotNetCore.CAP.MySql
PM> Install-Package DotNetCore.CAP.PostgreSql

Configuration

First,You need to config CAP in your Startup.cs：

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

	services.AddDbContext<AppDbContext>();

	services.AddCap(x =>
	{
		// If your SqlServer is using EF for data operations, you need to add the following configuration：
		// Notice: You don't need to config x.UseSqlServer(""") again!
		x.UseEntityFramework<AppDbContext>();

		// If you are using Dapper,you need to add the config：
		x.UseSqlServer("Your ConnectionStrings");
		//x.UseMySql("Your ConnectionStrings");
		//x.UsePostgreSql("Your ConnectionStrings");

		// If your Message Queue is using RabbitMQ you need to add the config：
		x.UseRabbitMQ("localhost");

		// If your Message Queue is using Kafka you need to add the config：
		x.UseKafka("localhost");
	});
}

public void Configure(IApplicationBuilder app)
{
	.....

	app.UseCap();
}

Publish

Inject ICapPublisher in your Controller, then use the ICapPublisher to send message

public class PublishController : Controller
{
	private readonly ICapPublisher _publisher;

	public PublishController(ICapPublisher publisher)
	{
		_publisher = publisher;
	}


	[Route("~/checkAccount")]
	public async Task<IActionResult> PublishMessage()
	{
		// Specifies the message header and content to be sent
		await _publisher.PublishAsync("xxx.services.account.check", new Person { Name = "Foo", Age = 11 });

		return Ok();
	}

	[Route("~/checkAccountWithTrans")]
	public async Task<IActionResult> PublishMessageWithTransaction([FromServices]AppDbContext dbContext)
	{
		using (var trans = dbContext.Database.BeginTransaction())
		{
			await _publisher.PublishAsync("xxx.services.account.check", new Person { Name = "Foo", Age = 11 });

			trans.Commit();
		}
		return Ok();
	}
}

Subscribe

Action Method

Add the Attribute [CapSubscribe()] on Action to subscribe message:

public class PublishController : Controller
{
	private readonly ICapPublisher _publisher;

	public PublishController(ICapPublisher publisher)
	{
		_publisher = publisher;
	}


	[NoAction]
	[CapSubscribe("xxx.services.account.check")]
	public async Task CheckReceivedMessage(Person person)
	{
		Console.WriteLine(person.Name);
		Console.WriteLine(person.Age);     
		return Task.CompletedTask;
	}
}

Service Method

If your subscribe method is not in the Controller,then your subscribe class need to Inheritance ICapSubscribe:

namespace xxx.Service
{
	public interface ISubscriberService
	{
		public void CheckReceivedMessage(Person person);
	}


	public class SubscriberService: ISubscriberService, ICapSubscribe
	{
		[CapSubscribe("xxx.services.account.check")]
		public void CheckReceivedMessage(Person person)
		{

		}
	}
}

Then inject your ISubscriberService class in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
	services.AddTransient<ISubscriberService,SubscriberService>();
}

Dashboard

CAP 2.1 and above provides the dashboard pages, you can easily view the sent and received messages. In addition, you can also view the message status in real time on the dashboard.

In the distributed environment, the dashboard built-in integrated Consul as a node discovery, while the realization of the gateway agent function, you can also easily view the node or other node data, It’s like you are visiting local resources.

services.AddCap(x =>
{
    //...
    
    // Register Dashboard
    x.UseDashboard();
    
    // Register to Consul
    x.UseDiscovery(d =>
    {
        d.DiscoveryServerHostName = "localhost";
        d.DiscoveryServerPort = 8500;
        d.CurrentNodeHostName = "localhost";
        d.CurrentNodePort = 5800;
        d.NodeId = 1;
        d.NodeName = "CAP No.1 Node";
    });
});

Contribute

One of the easiest ways to contribute is to participate in discussions and discuss issues. You can also contribute by submitting pull requests with code changes.

License

MIT