asp.net core监控—引入Prometheus（三）

上一篇博文中说到Prometheus有四种指标类型：Counter（计数器）、Gauge（仪表盘）、Histogram（直方图）、Summary（摘要），并且我们做了一个Counter的Demo，接下来看看Gauge。

2、Gauge：仪表盘，有增有减

这个指标非常像汽车的车速表，指针是在一定范围内有增有减的。下面我们接着上一篇博文的Sample来说，现在需要实时监控处在下“单完成”，“支付完成”，“发货完成”的单据数据，和各三种状态的占比；我们知道一个订单在一个时刻只能是一种状态，我们可以在下单时增加计数order的指标，但当订单从order转到pay状态后，pay指标会增加，同时order指标会减少，这个场景就会用上了Gauge了。

有了这个思路，我们可以上手代码了，BusinessController的代码不变（因为我们实现了业务逻辑代码和监控数据指标采集分离），这里我们需要在MetricsHub.cs中添加Gauge类型的指标收集集合：

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

因为在上面分析中，我们一个动作，比如pay时，会触发两个指标的改变，order指标减少，pay指标增加，所以Gauge是一个Dictionary<string, Dictionary<string, Gauge>>类型，内部的字典存放减少和增加的Gauge的监控指标对象。

接下来就要在BusinessMetricsMiddleware的中间件中添加处理Gauge指标增加减少的代码了：

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Countervar counter = metricsHub.GetCounter(context.Request.Path);if (counter != null){//计数counter.Inc();}var gauges = metricsHub.GetGauge(context.Request.Path);if (gauges != null){//存在增加指标+就Incif (gauges.ContainsKey("+")){gauges["+"].Inc();} //存在减少指标-就Decif (gauges.ContainsKey("-")){gauges["-"].Dec();}}}}}}finally{context.Response.Body = originalBody;}}}
}

再就是在Starsup中配置对应url的Gauge参数了：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;
using Prometheus;
using PrometheusSample.Middlewares;
using PrometheusSample.Services;
using System.Collections.Generic;
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  /metricsendpoints.MapMetrics();endpoints.MapControllers();});}/// <summary>/// 处理监控事项/// </summary>/// <param name="services"></param>void MetricsHandle(IServiceCollection services){var metricsHub = new MetricsHub();//countermetricsHub.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。"));//gaugevar orderGauge = Metrics.CreateGauge("business_order_count", "当前下单数量。");var payGauge = Metrics.CreateGauge("business_pay_count", "当前支付数量。");var shipGauge = Metrics.CreateGauge("business_ship_count", "当前发货数据。");metricsHub.AddGauge("/order", new Dictionary<string, Gauge> {{ "+", orderGauge}});metricsHub.AddGauge("/pay", new Dictionary<string, Gauge> {{"-",orderGauge},{"+",payGauge}});metricsHub.AddGauge("/ship", new Dictionary<string, Gauge> {{"+",shipGauge},{"-",payGauge}});services.AddSingleton(metricsHub);}}
}

最后一步，就是打开Grafana来配置展示图表了

订单状态数据仪表盘