.NET Core微服务三：polly熔断与降级
本文的项目代码，在文章结尾处可以下载。
本文使用的环境：Windows10 64位 + VS 2019 + .NET Core 3.1
Consul有关介绍：https://www.jianshu.com/p/32dc52f28a14
Consul官方网址：https://www.consul.io/
一、安装Consul
1.官网下载对应版本，并解压出来
2.打开cmd，cd到解压的目录，运行如下其中一条命令
本次演示都在同一台计算机上，所以本文选择命令一；这两条命令请在开发环境使用，生产环境不要使用。
命令一：“consul.exe agent -dev”服务中心的ip地址，将会使用127.0.0.1
命令二：“consul.exe agent -dev -client x.x.x.x”指定服务中心的ip地址
3.命令运行成功后，打开“http://127.0.0.1:8500/”，出现如下画面
二、创建服务
1.服务端项目大体结构：
2.新建.NET Core类库项目，命名为“ClassLibrary”，然后NuGet搜索并安装
“Consul”、“Microsoft.Extensions.Configuration”、“Microsoft.Extensions.Configuration.Json”
Common.cs代码：
using Consul;
using Microsoft.Extensions.Configuration;
using System; namespace ClassLibrary
{
public class Common
{
public static IConfiguration Configuration { get; }
static Common()
{
Configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json", false, true).Build();
} /// <summary>
/// 需要注册的服务地址
/// </summary>
public static string ConsulServiceIP
{
get
{
return Configuration["Consul:ServiceIP"];
}
} /// <summary>
/// 需要注册的服务端口
/// </summary>
public static int ConsulServicePort
{
get
{
string str = Configuration["Consul:ServicePort"];
return int.Parse(str);
}
} /// <summary>
/// 服务注册
/// </summary>
public static void ConsulRegister()
{
ConsulClient client = new ConsulClient(
(ConsulClientConfiguration c) =>
{
c.Address = new Uri(Configuration["Consul:Address"]); //Consul服务中心地址
c.Datacenter = Configuration["Consul:DataCenter"]; //指定数据中心，如果未提供，则默认为代理的数据中心。
}
);
string checkUrl = Configuration["Consul:CheckUrl"];
client.Agent.ServiceRegister(new AgentServiceRegistration()
{
ID = Guid.NewGuid().ToString(), //服务编号，不可重复
Name = Configuration["Consul:ServiceName"], //服务名称
Port = ConsulServicePort, //本程序的端口号
Address = ConsulServiceIP, //本程序的IP地址
Check = new AgentServiceCheck()
{
DeregisterCriticalServiceAfter = TimeSpan.FromMilliseconds(), //服务停止后多久注销
Interval = TimeSpan.FromSeconds(), //服务健康检查间隔
Timeout = TimeSpan.FromSeconds(), //检查超时的时间
HTTP = $"http://{ConsulServiceIP}:{ConsulServicePort}{checkUrl}" //检查的地址
}
});
} }
}
3.新建.NET Core的webapi项目，命名为“ServiceStudent”，把“为HTTPS配置”的勾选去掉
Controller代码：
using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic; namespace ServiceStudent.Controllers
{
[Route("api/[controller]/[action]")]
[ApiController]
public class DefaultController : ControllerBase
{
static List<Student> list = new List<Student>() {
new Student(){ ID = "", StudentName = "学生1", StudentAge = },
new Student(){ ID = "", StudentName = "学生2", StudentAge = },
new Student(){ ID = "", StudentName = "学生3", StudentAge = }
}; /// <summary>
/// 健康检查接口
/// </summary>
[HttpGet]
public string Check()
{
return "";
} [HttpGet]
public List<Student> GetList()
{
Console.WriteLine(DateTime.Now.ToString());
return list;
} [HttpGet]
public Student GetModel(string id)
{
Console.WriteLine(DateTime.Now.ToString());
return list.Find(t => t.ID == id);
}
}
}
其中有一段健康检查的接口，作用是让服务中心知道服务没有挂掉还能访问，不需要什么业务，所以怎么简单怎么来：
Model代码：
public class Student
{
public string ID { get; set; }
public string StudentName { get; set; }
public int StudentAge { get; set; }
}
appsettings.json的配置，加入"Consul"，注意ServiceIP改为自己电脑的IP（这个不要配置为127.0.0.1，后面访问会不正常）
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*",
"Consul": {
"Address": "http://127.0.0.1:8500",
"CheckUrl": "/api/Default/Check",
"DataCenter": "dc1",
"ServiceIP": "192.168.2.119",
"ServicePort": ,
"ServiceName": "Student"
}
}
Program.cs的CreateHostBuilder方法改为：
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
string ip = Common.ConsulServiceIP;
int port = Common.ConsulServicePort;
webBuilder.UseStartup<Startup>().UseUrls($"http://{ip}:{port}");
});
在Startup.cs的Configure方法中加入“ClassLibrary.Common.ConsulRegister();”
这样一个“Student”服务就创建好了，“Teacher”服务也是如法炮制，但是需要改appsettings.json的服务名和端口号，代码就不贴了，请到文章结尾处下载。
三、启动服务
通过命令行来启动，打开cmd，cd到Debug目录，各自运行“dotnet ServiceStudent.dll”和“dotnet ServiceTeacher.dll”。
请检查端口有没有被占用或超出范围，如果失败了，在配置文件中换成其它端口试试。
服务运行成功后，打开“http://127.0.0.1:8500/”，如下画面注册成功
如果出现一项打X，那就是失败，这个服务会在1分钟之后被踢出列表
一个服务可能会部署到多个服务器上，用“Teacher”来模拟下多台机器运行。
前面运行好的服务不要关闭，打开Teacher的Debug目录下的配置文件，
修改它的端口号，服务名不用改，再新开一个cmd，运行“dotnet ServiceTeacher.dll”
那么服务中心就会有变化
四、使用服务
1.客户端项目大体结构：
2.新建.net core类库项目，命名为“ClassLibrary”，然后NuGet搜索并安装
“Consul”、“Microsoft.Extensions.Configuration”
Common.cs代码：
using Consul;
using Microsoft.Extensions.Configuration;
using System;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks; namespace ClassLibrary
{
public class Common
{
public static IConfiguration Configuration { get; }
static Common()
{
Configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json", false, true).Build();
} public static string ConsulAddress
{
get { return Configuration["ConsulAddress"]; }
} /// <summary>
/// 获取服务
/// </summary>
public static string GetService(string serviceName)
{
ConsulClient client = new ConsulClient(c => c.Address = new Uri(ConsulAddress)); var response = client.Agent.Services().Result.Response; //服务名称区分大小写，若要不区分：Equals(serviceName, StringComparison.OrdinalIgnoreCase)
var services = response.Where(s => s.Value.Service.Equals(serviceName)).Select(s => s.Value); //进行取模，随机取得一个服务器，或者使用其它负载均衡策略
var service = services.ElementAt(Environment.TickCount % services.Count()); return service.Address + ":" + service.Port;
} /// <summary>
/// 获取服务（异步方法）
/// </summary>
public async Task<string> GetService2(string serviceName)
{
ConsulClient client = new ConsulClient(c => c.Address = new Uri(ConsulAddress)); var response = (await client.Agent.Services()).Response; //服务名称区分大小写，若要不区分：Equals(serviceName, StringComparison.OrdinalIgnoreCase)
var services = response.Where(s => s.Value.Service.Equals(serviceName)).Select(s => s.Value); //进行取模，随机取得一个服务器，或者使用其它负载均衡策略
var service = services.ElementAt(Environment.TickCount % services.Count()); return service.Address + ":" + service.Port;
} public static string HttpGetString(string url)
{
HttpClient httpClient = new HttpClient();
string result = httpClient.GetAsync(url)
.Result.Content.ReadAsStringAsync().Result;
httpClient.Dispose();
return result;
} public static T HttpGetObject<T>(string url)
{
string result = HttpGetString(url);
return Newtonsoft.Json.JsonConvert.DeserializeObject<T>(result);
} }
}
3.新建.NET Core的webapi项目，命名为“ClientSite”，把“为HTTPS配置”的勾选去掉
StudentController代码：
using ClassLibrary;
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic; namespace ClientSite.Controllers
{
[Route("api/[controller]/[action]")]
[ApiController]
public class StudentController : ControllerBase
{
[HttpGet]
public object GetList()
{
string ip = Common.GetService("Student");
List<Student> list = Common.HttpGetObject<List<Student>>($"http://{ip}/api/Default/GetList");
return new
{
address = ip,
data = list
};
} [HttpGet]
public object GetModel(string id)
{
string ip = Common.GetService("Student");
Student model = Common.HttpGetObject<Student>($"http://{ip}/api/Default/GetModel?id={id}");
return new
{
address = ip,
data = model
};
}
}
}
TeacherController代码：
using ClassLibrary;
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic; namespace ClientSite.Controllers
{
[Route("api/[controller]/[action]")]
[ApiController]
public class TeacherController : ControllerBase
{
[HttpGet]
public object GetList()
{
string ip = Common.GetService("Teacher");
List<Teacher> list = Common.HttpGetObject<List<Teacher>>($"http://{ip}/api/Default/GetList");
return new
{
address = ip,
data = list
};
} [HttpGet]
public object GetModel(string id)
{
string ip = Common.GetService("Teacher");
Teacher model = Common.HttpGetObject<Teacher>($"http://{ip}/api/Default/GetModel?id={id}");
return new
{
address = ip,
data = model
};
}
}
}
appsettings.json加入：
"ConsulAddress": "http://127.0.0.1:8500"
4.用VS启动站点，然后用postman访问
“http://ip:port/api/Student/GetList”
“http://ip:port/api/Student/GetModel?id=002”
多次访问“http://ip:port/api/Teacher/GetList”，则address会随机切换，注意看返回的端口号