First attempt at solving problems

0-limit-crawler/main.go

@@ -12,11 +12,12 @@ package main
 import (
 	"fmt"
 	"sync"
+	"time"
 )
 
 // Crawl uses `fetcher` from the `mockfetcher.go` file to imitate a
 // real crawler. It crawls until the maximum depth has reached.
-func Crawl(url string, depth int, wg *sync.WaitGroup) {
+func Crawl(url string, depth int, wg *sync.WaitGroup, throttle *time.Ticker) {
 	defer wg.Done()
 
 	if depth <= 0 {
@@ -35,14 +36,16 @@ func Crawl(url string, depth int, wg *sync.WaitGroup) {
 	for _, u := range urls {
 		// Do not remove the `go` keyword, as Crawl() must be
 		// called concurrently
-		go Crawl(u, depth-1, wg)
+		<-throttle.C
+		go Crawl(u, depth-1, wg, throttle)
 	}
 }
 
 func main() {
 	var wg sync.WaitGroup
 
 	wg.Add(1)
-	Crawl("http://golang.org/", 4, &wg)
+	throttle := time.NewTicker(2 * time.Second)
+	Crawl("http://golang.org/", 4, &wg, throttle)
 	wg.Wait()
 }

1-producer-consumer/main.go

@@ -10,22 +10,25 @@ package main
 
 import (
 	"fmt"
+	"sync"
 	"time"
 )
 
-func producer(stream Stream) (tweets []*Tweet) {
+func producer(stream Stream, conn chan *Tweet, wg *sync.WaitGroup) {
+	wg.Done()
 	for {
 		tweet, err := stream.Next()
 		if err == ErrEOF {
-			return tweets
+			close(conn)
+			return
 		}
-
-		tweets = append(tweets, tweet)
+		conn <- tweet
 	}
 }
 
-func consumer(tweets []*Tweet) {
-	for _, t := range tweets {
+func consumer(conn chan *Tweet, wg *sync.WaitGroup) {
+	defer wg.Done()
+	for t := range conn {
 		if t.IsTalkingAboutGo() {
 			fmt.Println(t.Username, "\ttweets about golang")
 		} else {
@@ -38,11 +41,16 @@ func main() {
 	start := time.Now()
 	stream := GetMockStream()
 
+	conn := make(chan *Tweet)
+	var wg sync.WaitGroup
+	wg.Add(2)
 	// Producer
-	tweets := producer(stream)
+	go producer(stream, conn, &wg)
 
 	// Consumer
-	consumer(tweets)
+	go consumer(conn, &wg)
+
+	wg.Wait()
 
 	fmt.Printf("Process took %s\n", time.Since(start))
 }

3-limit-service-time/main.go

@@ -10,6 +10,8 @@
 
 package main
 
+import "time"
+
 // User defines the UserModel. Use this to check whether a User is a
 // Premium user or not
 type User struct {
@@ -21,8 +23,19 @@ type User struct {
 // HandleRequest runs the processes requested by users. Returns false
 // if process had to be killed
 func HandleRequest(process func(), u *User) bool {
-	process()
-	return true
+
+	timer := time.NewTimer(10 * time.Second)
+	done := make(chan bool)
+	go func() {
+		process()
+		done <- true
+	}()
+	select {
+	case <-timer.C:
+		return false
+	case <-done:
+		return true
+	}
 }
 
 func main() {