Implement random sleep durations

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

Author: alexellis

Diff for: sleep/handler.go

@@ -3,13 +3,44 @@ package function
 import (
 	"fmt"
 	"log"
+	"math/rand"
 	"os"
 	"time"
 )
 
+var r *rand.Rand
+
+func init() {
+
+	r = rand.New(rand.NewSource(time.Now().Unix()))
+}
+
 // Handle a serverless request
+// 1. When no headers are given, sleep for the environment variable: sleep_duration.
+// 2. When an X-Sleep header is given, sleep for that amount of time.
+// 3. When the X-Min-Sleep and X-Max-Sleep headers are given, sleep for a random amount
+// of time between those two figures
 func Handle(req []byte) string {
 
+	if minV, ok := os.LookupEnv("Http_X_Min_Sleep"); ok && len(minV) > 0 {
+		if maxV, ok := os.LookupEnv("Http_X_Max_Sleep"); ok && len(maxV) > 0 {
+			minSleep, _ := time.ParseDuration(minV)
+			maxSleep, _ := time.ParseDuration(maxV)
+
+			minMs := minSleep.Milliseconds()
+			maxMs := maxSleep.Milliseconds()
+
+			randMs := r.Int63n(maxMs-minMs) + minMs
+
+			sleepDuration, _ := time.ParseDuration(fmt.Sprintf("%dms", randMs))
+
+			log.Printf("Start sleep for: %fs\n", sleepDuration.Seconds())
+			time.Sleep(sleepDuration)
+			log.Printf("Sleep done for: %fs\n", sleepDuration.Seconds())
+			return fmt.Sprintf("Slept for: %fs", sleepDuration.Seconds())
+		}
+	}
+
 	sleepDuration := time.Second * 2
 
 	if val, ok := os.LookupEnv("Http_X_Sleep"); ok && len(val) > 0 {