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。

2、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>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
{
/// /// 请求记录中间件 ///
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();
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();
});
}
/// /// 处理监控事项 ///
///
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