之前的Counters都是系统内置的，我们只需在进程外，或进程内采集，然后交给专门的展示指标工具即可。本篇说一下自定义EventSource，来采集自己业务中，或自己产品中的指标收集方式。
自定义EventSource是以EventCounters作为核心，EventCounters的作用是实时自动定期推送指标到侦听器的。
在自定义EventSource时，可以使用四种EventCounter：
EventCounter：统计指标收集器，比如平均值，最大值，最小值
PollingCounter：自定义统计指标收集器，通过自定义统计方法的方式实现对指标的统计
IncrementingEventCounter：累加指标收集器，采集一定时间段内的指标汇总
IncrementingPollingCounter：自定义累加指标收集器，通过自定义累函数，实现指标收集
本例先说一下用EventCounter实现自定义EventSource。
本例是定义了一个WorkingEventSouce事件源，定义了WorkingEventListener监听器，和发送指标采集指标的类型EventCounterDemo。
WorkingEventSouce事件源
/// <summary>
/// Working业务事件源
/// </summary>
[EventSource(Name = "WorkingEventSource")]
public sealed class WorkingEventSource : EventSource
{public static readonly WorkingEventSource Instance = new WorkingEventSource();private EventCounter _workingCounter;private WorkingEventSource(){_workingCounter = new EventCounter("working-time", this){DisplayName = "Working Time",DisplayUnits = "ms"};} /// <summary>/// Working发送业务指标/// </summary>/// <param name="elapsedMilliseconds"></param>public void Working(long elapsedMilliseconds){_workingCounter?.WriteMetric(elapsedMilliseconds);}protected override void Dispose(bool disposing){_workingCounter?.Dispose();_workingCounter = null;base.Dispose(disposing);}
}
WorkingEventListener监听器
/// <summary>
/// 指标输出委托
/// </summary>
/// <param name="key"></param>
/// <param name="value"></param>
public delegate void WriteContent(string key, string value);
/// <summary>
/// 指标监听器
/// </summary>
public class WorkingEventListener : EventListener
{protected readonly string[] _countersName = new string[] { "WorkingEventSource" };public event WriteContent WriteEvent;protected override void OnEventSourceCreated(EventSource source){if (_countersName.Contains(source.Name)){EnableEvents(source, EventLevel.Verbose, EventKeywords.All, new Dictionary<string, string>(){["EventCounterIntervalSec"] = "1"});}}protected override void OnEventWritten(EventWrittenEventArgs eventData){if (eventData.EventName.Equals("EventCounters")){for (int i = 0; i < eventData.Payload.Count; ++i){if (eventData.Payload[i] is IDictionary<string, object> eventPayload){var counterName = "";var counterValue = "";if (eventPayload.TryGetValue("DisplayName", out object displayValue)){counterName = displayValue.ToString();}if (eventPayload.TryGetValue("Mean", out object value) ||eventPayload.TryGetValue("Increment", out value)){counterValue = value.ToString();}WriteEvent(counterName, counterValue);}}}}
}
发送指标采集指标的类型EventCounterDemo
public class EventCounterDemo
{public static void Run(){var listener = new WorkingEventListener();listener.WriteEvent += Listener_WriteEvent;new Thread(Working).Start();}//以控制台方式展示采集到的指标private static void Listener_WriteEvent(string key, string value){Console.WriteLine($"{key}：{value}");}/// <summary>/// 模拟写业务指标，每秒写两次，i递增/// </summary>static void Working(){int i = 0;while (true){var count = i;Console.WriteLine(count);WorkingEventSource.Instance.Working(count);System.Threading.Thread.Sleep(500);i += 1;}}
}
调用方法：
class Program{static void Main(){EventCounterDemo.Run();Console.Read();}}
运行结果如下，可以看到，每少发送两次指标，而采集的结果是取其平均值展示了出来。
下图是跟踪EventListener的OnEventWritten的Payload有效载荷时的数据，可以看到有最大最小值，时间间隔，间隔里的次数，平均值，和当前指标类型为Mean等信息，这是EventCounter指标器的类型原因。
