1、什么是Ocelot

　　Ocelot是一个用.NET Core实现并且开源的API网关,它功能强大,包括了:路由、请求聚合、服务发现、认证、鉴权、限流熔断、并内置了负载均衡器与Service Fabric、Butterfly Tracing集成。

2、前期准备工作

　　新建一个Web API，返回IP+Port字符串（有利于我们直观感受）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace StudyGateway.Controllers
{
[ApiController]
[Route("api/[controller]")]
public class WeatherForecastController : ControllerBase
{
private IConfiguration _configuration;
public WeatherForecastController(IConfiguration configuration)
{
this._configuration = configuration;
}

    \[HttpGet\]  
    public string Get()  
    {  
        string ip = \_configuration\["IP"\];  
        string port = \_configuration\["Port"\];  
        return $@"{ip} {port}";  
    }  
}  

}

　　CMD启动该站点

dotnet StudyGateway.dll --urls="http://*:5177" --ip="127.0.0.1" --port=5177

　　显示截图：

　　

3、开始设计网关（Gateway）
　　创建一个新的Net Core Api项目，引用Ocelot包（注意版本对应 core 3.x 对应 Ocelot 15）

　　安装完成后，修改Startup，因为这个站点只是作为网关，所以只需要以下配置

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Ocelot.DependencyInjection;
using Ocelot.Middleware;

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

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)  
    {  
        services.AddOcelot(new ConfigurationBuilder().AddJsonFile("configuration.json").Build());  
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)  
    {  
        app.UseOcelot();  
    }  
}  

}

　　新增一个configuration.json，作为Ocelot的配置文件（记得修改 [复制到输出目录]）

　　配置下游站点

{
"ReRoutes": [
{
"DownstreamPathTemplate": "/api/{url}",
"DownstreamScheme": "http",
"DownstreamHostAndPorts": [
{
"Host": "127.0.0.1",
"Port": 5177
}
],
"UpstreamPathTemplate": "/GateWay/{url}", //这个url会转到上面的url
"UpstreamHttpMethod": [ "Get", "POST" ]
}
],
"GlobalConfiguration": {
"RequestIdKey": "OcRequestId",
"AdministrationPath": "/administration"
}
}

　　启动项目，访问

　　

　　成功转载！！！

4、负载均衡策略

　　前期准备工作的网站，通过CMD再启动一个新实例

dotnet StudyGateway.dll --urls="http://*:5178" --ip="127.0.0.1" --port=5178

　　修改Ocelot配置文件，新增一个下游站点

{
"ReRoutes": [
{
"DownstreamPathTemplate": "/api/{url}",
"DownstreamScheme": "http",
"DownstreamHostAndPorts": [
{
"Host": "127.0.0.1",
"Port": 5177
},
{
"Host": "127.0.0.1",
"Port": 5178
}
],
"UpstreamPathTemplate": "/GateWay/{url}", //这个url会转到上面的url
"UpstreamHttpMethod": [ "Get", "POST" ],
"LoadBalancerOptions": {
"Type": "RoundRobin" //负载均衡类型:轮询(其他类型也有,不一一列举了)
}
}
],
"GlobalConfiguration": {
"RequestIdKey": "OcRequestId",
"AdministrationPath": "/administration"
}
}

　　重新生成，访问：

　　

　　

5、缓存策略

　　安装Nuget包：Ocelot.Cache.CacheManager

　　修改Ocelot配置文件，添加FileCacheOptions节点

{
"ReRoutes": [
{
"DownstreamPathTemplate": "/api/{url}",
"DownstreamScheme": "http",
"DownstreamHostAndPorts": [
{
"Host": "127.0.0.1",
"Port": 5177
},
{
"Host": "127.0.0.1",
"Port": 5178
}
],
"UpstreamPathTemplate": "/GateWay/{url}", //这个url会转到上面的url
"UpstreamHttpMethod": [ "Get", "POST" ],
"LoadBalancerOptions": {
"Type": "RoundRobin" //负载均衡类型:轮询(其他类型也有,不一一列举了)
},
"FileCacheOptions": {
"TtlSeconds": 3,
"Region": "somename"
}
}
],
"GlobalConfiguration": {
"RequestIdKey": "OcRequestId",
"AdministrationPath": "/administration"
}
}

　　刷新

http://localhost:57789/GateWay/weatherforecast

　　访问后会缓存地址3秒。

　　比如：第一次访问，转载到Port=5177，3秒内都会访问5177