asp.net core监控—引入Prometheus（三）

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。

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