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Counter var 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Inc if (gauges.ContainsKey("+")) { gauges["+"].Inc(); } //存在减少指标-就Dec if (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 /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。")); //gauge var 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
订单状态比例图
最终的展示结果
上一篇中我们说过自定义业务计数器类型的步骤，其实仪盘的步骤也一样
1、分析业务，规划好监控跟踪指标
2、定义指标收集器
3、侵入编程(尽量在开发时分离业务实现与监控指票的收集代码)收集指标
4、开发grafana展示模板，完成展示
