Send spam messages in intervals of random length (rand.ExpFloat64)

packages/spammer/spammer.go

 package spammer
 
 import (
+	"math/rand"
 	"sync/atomic"
 	"time"
 
@@ -37,8 +38,6 @@ func (spammer *Spammer) Shutdown() {
 }
 
 func (spammer *Spammer) run(rate int, timeUnit time.Duration, processID int64) {
-	// emit messages every msgInterval interval
-	msgInterval := time.Duration(timeUnit.Nanoseconds() / int64(rate))
 	start := time.Now()
 
 	for {
@@ -54,6 +53,9 @@ func (spammer *Spammer) run(rate int, timeUnit time.Duration, processID int64) {
 		}
 
 		currentInterval := time.Since(start)
+
+		// emit messages by intervals whose random duration is exponentially distributed
+		msgInterval := time.Duration(float64(timeUnit.Nanoseconds()) * rand.ExpFloat64() / float64(rate))
 		if currentInterval < msgInterval {
 			//there is still time, sleep until msgInterval
 			time.Sleep(msgInterval - currentInterval)