背景
对于每隔几毫秒发生的事件,最好使每个事件的开销较低(小于一毫秒)。 否则,对性能的影响将很大。 记录事件意味着你将向磁盘写入内容。 如果磁盘不够快,你将丢失事件。 你需要一个解决方案,而不是记录事件本身。
在处理大量事件时,了解每个事件的度量值也无济于事。 大多数时候,你只需要一些统计信息。 因此,你可以在进程本身中获取统计信息,然后偶尔编写一个事件来报告统计信息,这是 EventCounter 将执行的操作。
代码实现
下面是有关如何实现 System.Diagnostics.Tracing.EventSource 的示例。 创建名为 MinimalEventCounterSource.cs 的新文件
- using System;
- using System.Collections.Generic;
- using System.Linq;
- using System.Threading.Tasks;
- using System.Diagnostics.Tracing;
- namespace WebApplication42
- {
- [EventSource(Name = "Sample.EventCounter.Minimal")]
- public sealed class MinimalEventCounterSource : EventSource
- {
- public static readonly MinimalEventCounterSource Log = new MinimalEventCounterSource();
- private EventCounter _requestCounter;
- private MinimalEventCounterSource() =>
- _requestCounter = new EventCounter("request-time", this)
- {
- DisplayName = "Request Processing Time",
- DisplayUnits = "ms"
- };
- public void Request(string url, float elapsedMilliseconds)
- {
- Console.WriteLine("url:" + url + " elapsedMilliseconds:" + elapsedMilliseconds);
- WriteEvent(1, url, elapsedMilliseconds);
- _requestCounter?.WriteMetric(elapsedMilliseconds);
- }
- protected override void Dispose(bool disposing)
- {
- _requestCounter?.Dispose();
- _requestCounter = null;
- base.Dispose(disposing);
- }
- }
- }
添加操作筛选器,创建名为 LogRequestTimeFilterAttribute.cs 的新文件,并使用以下代码:
- using Microsoft.AspNetCore.Http.Extensions;
- using Microsoft.AspNetCore.Mvc.Filters;
- using System;
- using System.Collections.Generic;
- using System.Diagnostics;
- using System.Linq;
- using System.Threading.Tasks;
- namespace WebApplication42
- {
- public class LogRequestTimeFilterAttribute : ActionFilterAttribute
- {
- private readonly Stopwatch _stopwatch = new Stopwatch();
- public override void OnActionExecuting(ActionExecutingContext context) => _stopwatch.Start();
- public override void OnActionExecuted(ActionExecutedContext context)
- {
- _stopwatch.Stop();
- MinimalEventCounterSource.Log.Request(
- context.HttpContext.Request.GetDisplayUrl(), _stopwatch.ElapsedMilliseconds);
- }
- }
- }
操作筛选器在请求开始时启动 Stopwatch,并在其完成后停止,捕获运行时间。 总毫秒数记录到 MinimalEventCounterSource 单一实例。 为了应用此筛选器,需要将其添加到筛选器集合。 在 Startup.cs 文件中,更新包含此筛选器的 ConfigureServices 方法。
- // This method gets called by the runtime. Use this method to add services to the container.
- public void ConfigureServices(IServiceCollection services)
- {
- services.AddControllers(options => options.Filters.Add<LogRequestTimeFilterAttribute>());
- services.AddSwaggerGen(c =>
- {
- c.SwaggerDoc("v1", new OpenApiInfo { Title = "WebApplication42", Version = "v1" });
- });
- }
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:70
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:19
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:18
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:19
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:22
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:17
- url:https://localhost:5008/WeatherForecast elapsedMilliseconds:17