asp.net core监控—引入Prometheus（五）

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　　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();
                                }
                            }
                            
                            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  /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}
            });
            
            //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。

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