asp.net core监控—引入Prometheus（二）

上一篇博文中，说明了怎么引进Prometheus到asp.net core项目中，因为是Demo，所以Prometheus和Grafana都是windows版本，本地执行的，生产环境上这些服务可以根据的公司的架构，放到适合的环境内，现在这些服务都支持跨平台化和容器化。并且在上篇博客中展示的是http请求的基础信息模板，本篇博客介绍自定义Prometheusr指标类型。

Prometheus有四种指标类型：Counter（计数器）、Gauge（仪表盘）、Histogram（直方图）、Summary（摘要），如果对业务的指标进行收集展示，在项目中是侵入式编程的，如果项目使用Prometheus.net进行对接Permetheus，是通过该包中的静态方法 Metrics.CreateCounter(),Metrics.CreateGauge(),Metrics.CreateSummary(),Metrics.CreateHistogram()来创建静态指标收集器，完成对业务指标收集的。

我们先来看具体Demo。

1、Counter：计数器，只增不减

先设置个业务场景：比如做一个商城，有用户注册(/register)，下订单(/order)，支付(/pay)，发货(/ship)四个API，代码如下：

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using PrometheusSample.Models;
using PrometheusSample.Services;
using System;
using System.Threading.Tasks;

namespace PrometheusSample.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class BusinessController : ControllerBase
    {
        private readonly ILogger<BusinessController> _logger;
        private readonly IOrderService _orderService;

        public BusinessController(ILogger<BusinessController> logger, IOrderService orderService)
        {
            _orderService = orderService;
            _logger = logger;
        }
        /// <summary>
        /// 注册
        /// </summary>
        /// <param name="username">用户名</param>
        /// <returns></returns>
        [HttpPost("/register")]
        public async Task<IActionResult> RegisterUser([FromBody] User user)
        {
            try
            {
                _logger.LogInformation("用户注册");
                var result = await _orderService.Register(user.UserName);
                if (result)
                {
                    return new JsonResult(new { Result = true });
                }
                else
                {
                    return new JsonResult(new { Result = false });
                }
            }
            catch (Exception exc)
            {
                _logger.LogCritical(exc, exc.Message);
                return new JsonResult(new { Result = false, Message = exc.Message });
            }
        }

        [HttpGet("/order")]
        public IActionResult Order(string orderno)
        {
            try
            {
                _logger.LogInformation("下单");             
                return new JsonResult(new { Result = true });
            }
            catch (Exception exc)
            {
                _logger.LogCritical(exc, exc.Message);
                return new JsonResult(new
                {
                    Result = false,
                    Message = exc.Message
                });
            }
        }
        [HttpGet("/pay")]
        public IActionResult Pay()
        {
            try
            {
                _logger.LogInformation("支付");
                return new JsonResult(new { Result = true });
            }
            catch (Exception exc)
            {
                _logger.LogCritical(exc, exc.Message);
                return new JsonResult(new { Result = false, Message = exc.Message });
            }
        }
        [HttpGet("/ship")]
        public IActionResult Ship()
        {
            try
            {
                _logger.LogInformation("发货");
                return new JsonResult(new { Result = true });
            }
            catch (Exception exc)
            {
                _logger.LogCritical(exc, exc.Message);
                return new JsonResult(new { Result = false, Message = exc.Message });
            }
        }
    }
}

上面是基本的业务Controller，为了降低依赖，我们的业务指标收集统一到一个中间件中去收集，中间件根据请求的url，和返回的数据结果数据进行业务指标数据的收集，当然也可以引入action过滤器或MediatR等中介者模式的组件来隔离业务逻辑的开发与监控数据的采集。

本例是用中间件的方式，首先定义一个静态的指标收集器：

 public class MetricsHub
    {
        private static Dictionary<string, Counter> _counterDictionary = new Dictionary<string, Counter>();
         public Counter GetCounter(string key)
        {
            if (_counterDictionary.ContainsKey(key))
            {
                return _counterDictionary[key];
            }
            else
            {
                return null;
            }
        }
        public void AddCounter(string key, Counter counter)
        {
            _counterDictionary.Add(key, counter);
        }
    }

　　定义中间件BusinessMetricsMiddleware

using Microsoft.AspNetCore.Http;
using PrometheusSample.Models;
using System.IO;
using System.Threading.Tasks;

namespace PrometheusSample.Middlewares
{
    /// <summary>
    /// 请求记录中间件
    /// </summary>
    public class BusinessMetricsMiddleware
    {
        private readonly RequestDelegate _next;
        public BusinessMetricsMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task InvokeAsync(HttpContext context, MetricsHub metricsHub)
        {
            var originalBody = context.Response.Body;
            try
            {
                using (var memStream = new MemoryStream())
                {
                    //从管理返回的Response中取出返回数据，根据返回值进行监控指标计数
                    context.Response.Body = memStream;
                    await _next(context);

                    memStream.Position = 0;
                    string responseBody = new StreamReader(memStream).ReadToEnd();
                    memStream.Position = 0;
                    await memStream.CopyToAsync(originalBody);
                    if (metricsHub.GetCounter(context.Request.Path) != null || metricsHub.GetGauge(context.Request.Path) != null)
                    {
                        //这里约定所有action返回值是一个APIResult类型
                        var result = System.Text.Json.JsonSerializer.Deserialize<APIResult>(responseBody, new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
                        if (result != null && result.Result)
                        {
                            //获取到Counter
                            var counter = metricsHub.GetCounter(context.Request.Path);
                            if (counter != null)
                            {
                                //计数
                                counter.Inc();
                            }
                        }
                    }
                }
            }
            finally
            {
                context.Response.Body = originalBody;
            }
        }
    }
}

中间件中，只要action请求返回的Result为true，就会计数，这样做的前提条件是业务返回值有统一约定；但每个action返回不可能都一样的，如果有特例，可以用action过滤器或中介者模式组件来对应。

再看一下Starup中是怎么配置这个中间件的：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;
using Prometheus;
using PrometheusSample.Middlewares;
using PrometheusSample.Services;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

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

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            MetricsHandle(services);
            services.AddScoped<IOrderService, OrderService>();
            services.AddControllers();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "PrometheusSample", Version = "v1" });
            });
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "PrometheusSample v1"));
            }

            app.UseRouting();
            //http请求的中间件
            app.UseHttpMetrics();
            app.UseAuthorization();

            //自定义业务跟踪
            app.UseBusinessMetrics();

            app.UseEndpoints(endpoints =>
            {
                //映射监控地址为  /metrics
                endpoints.MapMetrics();
                endpoints.MapControllers();
            });
        }
        /// <summary>
        /// 处理监控事项
        /// </summary>
        /// <param name="services"></param>
        void MetricsHandle(IServiceCollection services)
        {
            var metricsHub = new MetricsHub();
            //counter
            metricsHub.AddCounter("/register", Metrics.CreateCounter("business_register_user", "注册用户数。"));
            metricsHub.AddCounter("/order", Metrics.CreateCounter("business_order_total", "下单总数。"));
            metricsHub.AddCounter("/pay", Metrics.CreateCounter("business_pay_total", "支付总数。"));
            metricsHub.AddCounter("/ship", Metrics.CreateCounter("business_ship_total", "发货总数。"));
            services.AddSingleton(metricsHub);
        }
    }
}