Net Core Consul

     Consul 是HashiCorp公司推出的开源工具，用于实现分布式系统的服务发现与配置，内置了服务注册发现框架，分布式一致性实现，健康检查，负载均衡，服务治理，多数据中心方案等。Consul用GoLang语言实现，因此具有天然可移植性(支持Linux，Window和Mac OS)，安装包仅包含一个可执行文件(consul.exe),方便部署，与Docker等轻量级容器可无缝链接。

     要想利用Consul提供的服务实现服务的注册与实现，我们需要建立Consul Cluster，在Consul方案中，每个提供服务的节点上都要部署和运行Consul的Client Agent，所有运行Consul Agent节点的集合构成Consul Cluster。Consul Agent有两种运行模式：Server和Client。这里的Server和CLient只是Consul集群层面的区分，与搭建在Cluster之上的应用服务无关，以Server模式运行的Consul Agent节点用于维护Consul集群的状态，官方建议每个Consul Cluster至少有3个或以上的运行在Server Mode的Agent，Client节点不限。
    Consul支持多数据中心，每个数据中心的Consul Cluster都会运行于Server模式下的Agent节点中选出一个Leader节点，这个选举过程通过Consul实现Raft协议保证，多个Server节点上的Consul数据信息是强一致的，处于Client Mode的Consul Agent节点比较简单，无状态，仅仅负责将请求转发给Server Agent。

  Consul官网下载地址 Consul  解压文件，通过cmd指定解压文件路径

  本示例通过dev方式启动  如图所示:

服务注册到consul可以通过Http API （8500端口）,Consul client及Consul配置文件的方式。

1、下面介绍通过Consul Client API方式将service注册到Consul:

1)、appsettings.json consul节点配置信息

 "Consul": {
    "Address": "http://127.0.0.1:8500",
    "ServiceName": "ServiceA",
    "ServiceIP": "localhost",
    "ServicePort": "5000",
    "HealthCheck": "/HealthCheck"
  }

2)、Nuget package下载Consul(1.6.10.8)

 3)、Program配置Consul

builder.Services.AddSingleton<IConsulClient, ConsulClient>(p 
    => new ConsulClient(config => 
    {
        config.Address = new Uri(configuration["Consul:Address"]);
    }));

#region Consul
app.UseConsul(configuration, app.Lifetime);
#endregion

 public static class CousulExtension
    {
        public static IApplicationBuilder UseConsul(this IApplicationBuilder app, IConfiguration configuration, IHostApplicationLifetime lifetime)
        {
            var client = new ConsulClient(option => 
            {
                option.Address = new Uri(configuration["Consul:Address"]);
            });

            var registration = new AgentServiceRegistration
            {
                ID = Guid.NewGuid().ToString(),
                //Name = configuration["Consul:ServiceName"],
                //Address = configuration["Consul:ServiceIP"],
                //Port = Convert.ToInt32(configuration["Consul:ServicePort"]),
                //dotnet run --urls=https://localhost:5001 --ip=localhost --port=5001 --service=serviceA 
                Name = configuration["service"],
                Address = configuration["ip"],
                Port = Convert.ToInt32(configuration["port"]),
                Check = new AgentServiceCheck
                {
                    DeregisterCriticalServiceAfter = TimeSpan.FromSeconds(5),
                    Interval = TimeSpan.FromSeconds(10),
                    //HTTP = $"https://{configuration["Consul:ServiceIP"]}:{configuration["Consul:ServicePort"]}{configuration["Consul:HealthCheck"]}",
                    HTTP = $"https://{configuration["ip"]}:{configuration["port"]}{configuration["Consul:HealthCheck"]}",
                    Timeout = TimeSpan.FromSeconds(5)
                }
            };

            client.Agent.ServiceRegister(registration).GetAwaiter().GetResult();

            lifetime.ApplicationStopping.Register(() => 
            {
                client.Agent.ServiceDeregister(registration.ID).GetAwaiter().GetResult();
            });
            return app;
        }
    }

Notes: Register到Consul的service Id必须唯一，原因是通过Ocelot 集成Consul service需要指定ServiceName，如果Consul service需要负载均衡的话service要指定同一个ServiceName.

e.g.

 一个ServiceName有多个实例，从而可以做负载均衡。

4、创建一个NetCore API 项目，添加测试controller

 [HttpGet]
        public IActionResult Index([FromServices]IConfiguration configuration)
        {
            var result = new
            {
                msg = $"This is service1, current date: {DateTime.Now:G}",
                ip = configuration["ip"],
                port = configuration["port"]
            };
            return Ok(result);
        }

        [Authorize]
        [HttpGet("all")]
        public IActionResult Get([FromServices] IConfiguration configuration)
        {
            return Ok(
                new
                {
                    ID = 1,
                    Name = "consul service",
                    version = 1.0,
                    serviceIP = configuration["ip"],
                    servicePort = configuration["port"]
                });
        }

添加健康检查API Controller

[Route("[controller]")]
    [ApiController]
    public class HealthCheckController : Controller
    {
        [HttpGet]
        public IActionResult Index()
        {
            return Ok();
        }
    }

5、模拟服务集群创建多个服务实例分别注册到consul

dotnet run --urls=https://localhost:5001 --ip=localhost --port=5001 --service=serviceA

dotnet run --urls=https://localhost:5002 --ip=localhost --port=5002 --service=serviceA

dotnet run --urls=https://localhost:5003 --ip=localhost --port=5003 --service=serviceA

6、consul service

 

下面通过IConsulDiscoveryService测试是否可以正常从consul获取到服务

    public class ConsulDiscoveryService : IConsulDiscoveryService
    {
        private readonly IConfiguration _configuration;
        private IConsulClient _consulClient { get; set; }
        private readonly IHttpClientFactory _httpClientFactory;
        public ConsulDiscoveryService(IConfiguration configuration, IConsulClient consulClient, IHttpClientFactory httpClientFactory)
        {
            this._configuration = configuration;
            this._consulClient = new ConsulClient(options => 
            {
                options.Address = new Uri(_configuration["Consul:Address"]);
            });
            this._httpClientFactory = httpClientFactory;
        }

        public async Task<IEnumerable<HttpResponseMessage>> GetAsync()
        {
            var responses = new List<HttpResponseMessage>();
            var serviceNames = new List<string>() { "Service1" };
            var tasks = new List<Task>();
            foreach (var serviceName in serviceNames)
            {
                var task = Task.Run(async () =>
                {
                    var options = new QueryOptions
                    {
                        Datacenter = "dc1",
                        WaitTime = TimeSpan.FromMinutes(5)
                    };
                    var result = await _consulClient.Health.Service(serviceName, null, true, options);
                    var services = result.Response;
                    var serviceUrls = services.Select(s => $"https://{s.Service.Address}:{s.Service.Port}");
                    foreach (var serviceUrl in serviceUrls)
                    {
                        using var httpClient = _httpClientFactory.CreateClient();
                        var response = await httpClient.GetAsync($"{serviceUrl}/api/Service1/all");
                        responses.Add(response);
                    }
                });
                tasks.Add(task);
            }
            await Task.WhenAll(tasks);
            return responses;
        }
    }

将ConsulDiscoveryService添加到Configure Service中

builder.Services.AddTransient<IConsulDiscoveryService, ConsulDiscoveryService>();

验证

[HttpGet("consulservice")]
        public async Task<IActionResult> GetConsulDiscoveryService([FromServices]IConsulDiscoveryService service)
        {
            var result = await service.GetAsync();
            return Ok(result);
        }

 2、通过配置文件的方式注册service，这里只创建了一个NetCore API作为demo

  1)、Add一个.json 文件

{
  "services": [
    {
      "id": "consul_service01",
      "name": "service1",
      "tags": [
        "urlprefix-/ClientService01"
      ],
      "address": "localhost",
      "port": 5000,
      "checks": [
        {
          "name": "clientservice_check",
          "http": "https://localhost:5000/HealthCheck",
          "interval": "5s",
          "timeout": "5s"
        }
      ]
    }
  ]
}

 2)、以熟悉的方式启动NetCore API，例: dotnet run

 3)、启动consul，依然以dev方式启动，这里在实际使用中通常创建consul cluster，官方建议3-5个consul server，consul client数量不限

consul agent -dev -node MicServices -config-dir service.consul.json

4)、consul中查看注册的service

 

 5)、通过API查看服务

 

 

 OK, 可以正常获取consul下的所有services。