asp.net core監控—引入Prometheus（三）

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），並且我們做了一個Counter的Demo，接下來看看Gauge。

Gauge：儀表盤，有增有減
這個指標非常像汽車的車速表，指針是在一定範圍內有增有減的。下面我們接着上一篇博文的Sample來說，現在需要實時監控處在下“單完成”，“支付完成”，“發貨完成”的單據數據，和各三種狀態的佔比；我們知道一個訂單在一個時刻只能是一種狀態，我們可以在下單時增加計數order的指標，但當訂單從order轉到pay狀態後，pay指標會增加，同時order指標會減少，這個場景就會用上了Gauge了。
有了這個思路，我們可以上手代碼了，BusinessController的代碼不變（因爲我們實現了業務邏輯代碼和監控數據指標採集分離），這裏我們需要在MetricsHub.cs中添加Gauge類型的指標收集集合：

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);
    }
}

因爲在上面分析中，我們一個動作，比如pay時，會觸發兩個指標的改變，order指標減少，pay指標增加，所以Gauge是一個Dictionary<string, Dictionary<string, Gauge>>類型，內部的字典存放減少和增加的Gauge的監控指標對象。
接下來就要在BusinessMetricsMiddleware的中間件中添加處理Gauge指標增加減少的代碼了：

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)
                    {
                        //這裏約定所有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Counter  
                            var 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Inc      
                                if (gauges.ContainsKey("+"))
                                {
                                    gauges["+"].Inc();
                                }
                                //存在減少指標-就Dec    
                                if (gauges.ContainsKey("-"))
                                {
                                    gauges["-"].Dec();
                                }
                            }
                        }
                    }
                }
            }
            finally
            {
                context.Response.Body = originalBody;
            }
        }
    }
}

再就是在Starsup中配置對應url的Gauge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 =>    
            {                //映射監控地址爲  /metrics 
                endpoints.MapMetrics();   
                endpoints.MapControllers();     
            });    
        }      
        /// <summary>   
        /// 處理監控事項   
        /// </summary>   
        /// <param name="services"></param>   
         void MetricsHandle(IServiceCollection services) 
        {           
            var metricsHub = new MetricsHub();  
            //counter           
            metricsHub.AddCounter("/register", Metrics.CreateCounter("business_register_user", "註冊用戶數。"));    
            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。"));
            //gauge      
            var 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}      
            });      
            services.AddSingleton(metricsHub);      
        }   
    }
}

最後一步，就是打開Grafana來配置展示圖表了
訂單狀態數據儀表盤

訂單狀態比例圖

最終的展示結果

上一篇中我們說過自定義業務計數器類型的步驟，其實儀盤的步驟也一樣
1、分析業務，規劃好監控跟蹤指標
2、定義指標收集器
3、侵入編程(儘量在開發時分離業務實現與監控指票的收集代碼)收集指標
4、開發grafana展示模板，完成展示