GO by example, part 4

5-go-by-example/37-rate-limiting.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+// controlling resource utilization and maintaining quality of service
+func main() {
+
+	// basic rate limiting
+	// want to limit handling of incoming requests
+	requests := make(chan int, 5)
+	for i := 1; i <= 5; i++ {
+		requests <- i
+	}
+	close(requests)
+
+	// this limiter channel will receive a value every 200 milliseconds
+	// this is the regulator in the rate limiting scheme.
+	limiter := time.Tick(200 * time.Millisecond)
+
+	// by blocking on a receive from the limiter channel before serving each request,
+	// limit to 1 request every 200 milliseconds
+	for req := range requests {
+		<-limiter
+		fmt.Println("request", req, time.Now())
+	}
+
+	// allow short bursts of requests in rate limiting scheme while preserving the overall rate limit
+	// accomplish this by buffering the limiter channel
+	burstyLimiter := make(chan time.Time, 3)
+
+	// fill up the channel to represent allowed bursting
+	for i := 0; i < 3; i++ {
+		burstyLimiter <- time.Now()
+	}
+
+	// every 200 milliseconds try to add a new value to burstyLimiter, up to its limit of 3
+	go func() {
+		for t := range time.Tick(200 * time.Millisecond) {
+			burstyLimiter <- t
+		}
+	}()
+
+	// simulate 5 more incoming requests
+	// the first 3 of these will benefit from the burst capability of burstyLimiter
+	burstyRequests := make(chan int, 5)
+	for i := 1; i <= 5; i++ {
+		burstyRequests <- i
+	}
+	close(burstyRequests)
+	for req := range burstyRequests {
+		<-burstyLimiter
+		fmt.Println("request", req, time.Now())
+	}
+}