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Histogram。

3、Summary：摘要

summary是采集展示百分位数，百分位定义：在一组由小到大的数字中，某个数字大于90%的数字，这个数字就是第90个的百分位数。

通过demo的来理解一下吧，假如我们业务需求是要知道订单金额10，30，50，70，90的百分位数，该怎么实现呢？

需要在MetricsHub.cs中添加Summary类型的指标收集集合：

using Prometheus;
using System.Collections.Generic;namespace PrometheusSample.Middlewares
{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>>();private static Dictionary<string, Summary> _summaryDictionary = new Dictionary<string, Summary>();private static Dictionary<string, Histogram> _histogramDictionary = new Dictionary<string, Histogram>();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 Summary GetSummary(string key){if (_summaryDictionary.ContainsKey(key)){return _summaryDictionary[key];}else{return null;}}public Histogram GetHistogram(string key){if (_histogramDictionary.ContainsKey(key)){return _histogramDictionary[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);}public void AddSummary(string key, Summary summary){_summaryDictionary.Add(key, summary);}public void AddHistogram(string key, Histogram histogram){_histogramDictionary.Add(key, histogram);}}
}

接下来就要在BusinessMetricsMiddleware的中间件中添加处理Summary指标的代码了：

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();}}var histogram = metricsHub.GetHistogram(context.Request.Path);if (histogram != null){var parseResult = int.TryParse(result.Data.ToString(), out int i);if (parseResult){histogram.Observe(i);}}var summary = metricsHub.GetSummary(context.Request.Path);if (summary != null){var parseResult = int.TryParse(result.Data.ToString(), out int i);if (parseResult){summary.Observe(i);}}                            }}}}finally{context.Response.Body = originalBody;}}}
}

再就是在Starsup中配置对应url的Summary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}});//histogram   var orderHistogram = Metrics.CreateHistogram("business_order_histogram", "订单直方图。",new HistogramConfiguration{Buckets = Histogram.LinearBuckets(start: 1000, width: 1000, count: 6)}) ;         metricsHub.AddHistogram("/order", orderHistogram);//summary var orderSummary = Metrics.CreateSummary("business_order_summary", "10分钟内的订单数量",new SummaryConfiguration{Objectives = new[]{new QuantileEpsilonPair(0.1, 0.05),   new QuantileEpsilonPair(0.3, 0.05),      new QuantileEpsilonPair(0.5, 0.05),new QuantileEpsilonPair(0.7, 0.05),           new QuantileEpsilonPair(0.9, 0.05),}});metricsHub.AddSummary("/order", orderSummary);services.AddSingleton(metricsHub);}}
}

其实 new QuantileEpsilonPair(0.1, 0.05) 第一个参数是百分位，0.05是误差，范围是10%-5%，10%+5%。

最后一步，就是打开Grafana来配置展示图表了。

最终展示结果：

同时事例中给出了最大、最少、平均、汇总、当前值以供参考。