上一篇博文中說到Prometheus有四種指標類型：Counter（計數器）、Gauge（儀表盤）、Histogram（直方圖）、Summary（摘要），并且我們做了一個Counter的Demo，接下來看看Histogram。

3、Histogram：直方圖

直方圖，維基百科的定義：是一種對數據分布情況的圖形表示，是一種二維統計圖表，它的兩個坐標分別是統計樣本和該樣本對應的某個屬性的度量，以長條圖（bar）的形式具體表現。因為直方圖的長度及寬度很適合用來表現數量上的變化，所以較容易解讀差異小的數值。

還是拿上一篇的Sample來說明，假如每個訂單都有一個金額，在order時在返回值{result=true,data=1000}的data屬性中返回，這里，我們就可以用直方圖來收集這個金額，由于訂單的金額不一樣，我們就可以用直方圖來展示一定范圍金額內訂單的數據，監控出一定金額范圍內的訂單比例了。就是說在一定數量的訂單里，少于1000元的有多少個訂單，少于2000元有多少個訂單，少于3000元的有多少個訂單……

首先，我們得修改BusinessController中Order Action的業務邏輯，把訂單金額作為返回值：

[HttpGet("/order")]public IActionResult Order(string orderno){try{_logger.LogInformation("下單");//返回訂單金額var random = new Random();return new JsonResult(new { Result = true, data = random.Next(1, 8000) });}catch (Exception exc){_logger.LogCritical(exc, exc.Message);return new JsonResult(new{Result = false,Message = exc.Message});}}

這里的金額為了方便demo，是隨機生成一個1到8000的隨機數。

需要在MetricsHub.cs中添加Histogram類型的指標收集集合：

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,?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 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 AddHistogram(string key, Histogram histogram){_histogramDictionary.Add(key, histogram);}} }

接下來就要在BusinessMetricsMiddleware的中間件中添加處理Histogram指標的代碼了：

using Microsoft.AspNetCore.Http; using PrometheusSample.Models; using System.IO; using System.Threading.Tasks;namespace PrometheusSample.Middlewares {/// <summary>/// 請求記錄中間件/// </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()){//從管理返回的Response中取出返回數據，根據返回值進行監控指標計數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){//這里約定所有action返回值是一個APIResult類型var result = System.Text.Json.JsonSerializer.Deserialize<APIResult>(responseBody, new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });if (result != null && result.Result){//獲取到Countervar counter = metricsHub.GetCounter(context.Request.Path);if (counter != null){//計數counter.Inc();}var gauges = metricsHub.GetGauge(context.Request.Path);if (gauges != null){//存在增加指標+就Incif (gauges.ContainsKey("+")){gauges["+"].Inc();} //存在減少指標-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);}}}}}}finally{context.Response.Body = originalBody;}}} }

再就是在Starsup中配置對應url的Histogram參數了：

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請求的中間件app.UseHttpMetrics();app.UseAuthorization();//自定義業務跟蹤app.UseBusinessMetrics();app.UseEndpoints(endpoints =>{//映射監控地址為 /metricsendpoints.MapMetrics();endpoints.MapControllers();});}/// <summary>/// 處理監控事項/// </summary>/// <param name="services"></param>void MetricsHandle(IServiceCollection services){var metricsHub = new MetricsHub();//countermetricsHub.AddCounter("/register", Metrics.CreateCounter("business_register_user", "注冊用戶數。"));metricsHub.AddCounter("/order", Metrics.CreateCounter("business_order_total", "下單總數。"));metricsHub.AddCounter("/pay", Metrics.CreateCounter("business_pay_total", "支付總數。"));metricsHub.AddCounter("/ship", Metrics.CreateCounter("business_ship_total", "發貨總數。"));//gaugevar orderGauge = Metrics.CreateGauge("business_order_count", "當前下單數量。");var payGauge = Metrics.CreateGauge("business_pay_count", "當前支付數量。");var shipGauge = Metrics.CreateGauge("business_ship_count", "當前發貨數據。");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", "訂單直方圖。",new HistogramConfiguration{Buckets = Histogram.LinearBuckets(start: 1000, width: 1000, count: 5)});metricsHub.AddHistogram("/order",?orderHistogram);services.AddSingleton(metricsHub);}} }

Histogram.LinearBuckets(start: 1000, width: 1000, count: 5)是金額從1000開始，每1000為一個臺階，一共6個臺階：0~1000，1001~2000，2001~3000，3001~4000，4001~5000，還有一個是大于5000的。

最后一步，就是打開Grafana來配置展示圖表了。

訂單金額分布圖

訂單比例分布圖

圖中histogram_quantile(0.80, sum(rate(business_order_histogram_bucket[5m])) by (le))的意思是“80%的訂單金額小于等于這個值”5分鐘內的值。

最終展示結果：

聰明的你一定發現，這篇博文與上一篇如出一轍，是的，只是監控指標展示類型不同而以。

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