Go语言复杂事件处理（CEP）引擎的实现与探索

package main

import (
    "fmt"
    "time"

    "github.com/tideland/gocells/cells" // 假设的导入路径
)

// MyEvent 定义一个简单的事件结构
type MyEvent struct {
    Timestamp time.Time
    Value     float64
    Source    string
}

// SimpleProcessor 是一个自定义的事件处理器
type SimpleProcessor struct{}

// Process 方法实现了 cells.EventProcessor 接口
func (sp *SimpleProcessor) Process(event cells.Event) (cells.Event, error) {
    // 检查事件主题和负载类型
    if event.Topic() == "data_point" {
        if myEvent, ok := event.Payload().(MyEvent); ok {
            fmt.Printf("Processor received event from '%s' with value: %.2f\n", myEvent.Source, myEvent.Value)
            // 假设我们只关心高值事件
            if myEvent.Value > 100.0 {
                fmt.Printf("  -> High value detected! Triggering alert for value: %.2f\n", myEvent.Value)
                // 可以返回一个新的事件，例如一个“警报”事件
                return cells.NewEvent("high_value_alert", fmt.Sprintf("Alert: Value %f from %s is high!", myEvent.Value, myEvent.Source)), nil
            }
        }
    }
    return nil, nil // 不产生新的事件或错误
}

func main() {
    // 1. 创建一个单元环境
    env := cells.NewEnvironment()

    // 2. 创建一个事件源单元
    // sourceCell 负责生成或接收外部事件
    sourceCell := cells.NewSourceCell("event-source")
    env.Add(sourceCell)

    // 3. 创建一个处理单元
    // processorCell 使用 SimpleProcessor 来处理接收到的事件
    processorCell := cells.NewCell("value-processor", &SimpleProcessor{})
    env.Add(processorCell)

    // 4. 创建一个最终的接收单元，用于打印由处理器生成的“警报”事件
    alertPrinterCell := cells.NewCell("alert-printer", cells.NewEventProcessor(func(event cells.Event) (cells.Event, error) {
        if event.Topic() == "high_value_alert" {
            fmt.Printf("ALERT SYSTEM: %s\n", event.Payload())
        }
        return nil, nil
    }))
    env.Add(alertPrinterCell)

    // 5. 连接单元形成处理网络
    // 事件从 sourceCell 流向 processorCell
    sourceCell.AddReceiver(processorCell)
    // processorCell 生成的“high_value_alert”事件流向 alertPrinterCell
    processorCell.AddReceiver(alertPrinterCell)

    // 6. 启动环境
    env.Start()
    defer env.Stop() // 确保在main函数结束时停止环境

    // 7. 模拟发送事件
    fmt.Println("--- Sending events ---")
    sourceCell.Emit(cells.NewEvent("data_point", MyEvent{Timestamp: time.Now(), Value: 85.5, Source: "SensorA"}))
    time.Sleep(100 * time.Millisecond)
    sourceCell.Emit(cells.NewEvent("data_point", MyEvent{Timestamp: time.Now(), Value: 120.0, Source: "SensorB"}))
    time.Sleep(100 * time.Millisecond)
    sourceCell.Emit(cells.NewEvent("data_point", MyEvent{Timestamp: time.Now(), Value: 99.9, Source: "SensorA"}))
    time.Sleep(100 * time.Millisecond)
    sourceCell.Emit(cells.NewEvent("data_point", MyEvent{Timestamp: time.Now(), Value: 150.7, Source: "SensorC"}))
    time.Sleep(100 * time.Millisecond)

    fmt.Println("--- All events sent ---")
    // 给予足够的时间让所有goroutines完成处理
    time.Sleep(1 * time.Second)
}

--- Sending events ---
Processor received event from 'SensorA' with value: 85.50
Processor received event from 'SensorB' with value: 120.00
  -> High value detected! Triggering alert for value: 120.00
ALERT SYSTEM: Alert: Value 120.000000 from SensorB is high!
Processor received event from 'SensorA' with value: 99.90
Processor received event from 'SensorC' with value: 150.70
  -> High value detected! Triggering alert for value: 150.70
ALERT SYSTEM: Alert: Value 150.700000 from SensorC is high!
--- All events sent ---