barrier pattern in the book added

concurrency/mastering_concurrency_in_go/ch1/letter_channel_example.go

@@ -3,7 +3,6 @@ package ch1
 import (
 	"fmt"
 	"strings"
-	"sync"
 )
 
 var initialString string
@@ -11,8 +10,7 @@ var initialBytes []byte
 var stringLength int
 var finalString string
 var lettersProcessed int
-var applicationStatus bool
-var wg sync.WaitGroup
+var applicationStatusL bool
 
 func getLetters(gQ chan string) {
 	for i := range initialBytes {
@@ -22,7 +20,7 @@ func getLetters(gQ chan string) {
 func capitalizeLetters(gQ chan string, sQ chan string) {
 	for {
 		if lettersProcessed >= stringLength {
-			applicationStatus = false
+			applicationStatusL = false
 			break
 		}
 		select {
@@ -34,7 +32,7 @@ func capitalizeLetters(gQ chan string, sQ chan string) {
 	}
 }
 func RunLetter() {
-	applicationStatus = true
+	applicationStatusL = true
 	getQueue := make(chan string)
 	stackQueue := make(chan string)
 	initialString = `Four score and seven years ago our fathers
@@ -50,7 +48,7 @@ created equal.`
 	close(getQueue)
 	close(stackQueue)
 	for {
-		if applicationStatus == false {
+		if applicationStatusL == false {
 			fmt.Println("Done")
 			fmt.Println(finalString)
 			break

concurrency/mastering_concurrency_in_go/ch1/spider.go

@@ -0,0 +1,101 @@
+package ch1
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"sync"
+	"time"
+)
+
+var applicationStatus bool
+var urls []string
+var urlsProcessed int
+var foundUrls []string
+var fullText string
+var totalURLCount int
+var wg sync.WaitGroup
+var v1 int
+
+func readURLs(statusChannel chan int, textChannel chan string) {
+	time.Sleep(time.Millisecond * 1)
+	fmt.Println("Grabbing", len(urls), "urls")
+	for i := 0; i < totalURLCount; i++ {
+		fmt.Println("Url", i, urls[i])
+		resp, _ := http.Get(urls[i])
+		text, err := ioutil.ReadAll(resp.Body)
+		textChannel <- string(text)
+		if err != nil {
+			fmt.Println("No HTML body")
+		}
+		statusChannel <- 0
+	}
+}
+
+func addToScrapedText(textChannel chan string, processChannel chan bool) {
+	for {
+		select {
+		case pC := <-processChannel:
+			if pC == true {
+				// hang on
+			}
+			if pC == false {
+				close(textChannel)
+				close(processChannel)
+			}
+		case tC := <-textChannel:
+			fullText += tC
+		}
+	}
+}
+
+func evaluateStatus(statusChannel chan int, textChannel chan string, processChannel chan bool) {
+	for {
+		select {
+		case status := <-statusChannel:
+			fmt.Print(urlsProcessed, totalURLCount)
+			urlsProcessed++
+			if status == 0 {
+				fmt.Println("Got url")
+			}
+			if status == 1 {
+				close(statusChannel)
+			}
+			if urlsProcessed == totalURLCount {
+				fmt.Println("Read all top-level URLs")
+				processChannel <- false
+				applicationStatus = false
+			}
+		}
+	}
+}
+
+func RunSpider() {
+	applicationStatus = true
+	statusChannel := make(chan int)
+	textChannel := make(chan string)
+	processChannel := make(chan bool)
+	totalURLCount = 0
+	urls = append(urls, "http://www.mastergoco.com/index1.html")
+	urls = append(urls, "http://www.mastergoco.com/index2.html")
+	urls = append(urls, "http://www.mastergoco.com/index3.html")
+	urls = append(urls, "http://www.mastergoco.com/index4.html")
+	urls = append(urls, "http://www.mastergoco.com/index5.html")
+	fmt.Println("Starting spider")
+	urlsProcessed = 0
+	totalURLCount = len(urls)
+	go evaluateStatus(statusChannel, textChannel, processChannel)
+	go readURLs(statusChannel, textChannel)
+	go addToScrapedText(textChannel, processChannel)
+	for {
+		if applicationStatus == false {
+			fmt.Println(fullText)
+			fmt.Println("Done!")
+			break
+		}
+		select {
+		case sC := <-statusChannel:
+			fmt.Println("Message on StatusChannel", sC)
+		}
+	}
+}

concurrency/mastering_concurrency_in_go/main.go

@@ -4,5 +4,6 @@ import "github.com/jianhan/go-patterns/concurrency/mastering_concurrency_in_go/c
 
 func main() {
 	// ch1.Run()
-	ch1.RunLetter()
+	// ch1.RunLetter()
+	ch1.RunSpider()
 }

go_design_pattern_book/concurrent_pattern/barrier/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"time"
+)
+
+func main() {
+	barrier("http://httpbin.org/headers", "http://httpbin.org/User-Agen")
+}
+
+var timeoutMilliseconds int = 5000
+
+type barrierResp struct {
+	Err  error
+	Resp string
+}
+
+func barrier(endpoints ...string) {
+	requestNumber := len(endpoints)
+	in := make(chan barrierResp, requestNumber)
+	defer close(in)
+	responses := make([]barrierResp, requestNumber)
+	for _, endpoint := range endpoints {
+		go makeRequest(in, endpoint)
+	}
+	var hasError bool
+	for i := 0; i < requestNumber; i++ {
+		resp := <-in
+		if resp.Err != nil {
+			fmt.Println("ERROR: ", resp.Err)
+			hasError = true
+			break
+		}
+		responses[i] = resp
+	}
+
+	if !hasError {
+		for _, resp := range responses {
+			fmt.Println(resp.Resp)
+		}
+	}
+}
+
+func makeRequest(out chan<- barrierResp, url string) {
+	res := barrierResp{}
+	client := http.Client{
+		Timeout: time.Duration(time.Duration(timeoutMilliseconds) * time.Millisecond),
+	}
+
+	resp, err := client.Get(url)
+	if err != nil {
+		res.Err = err
+		out <- res
+		return
+	}
+
+	byt, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		res.Err = err
+		out <- res
+		return
+	}
+
+	res.Resp = string(byt)
+	out <- res
+}

go_design_pattern_book/concurrent_pattern/barrier/main_test.go

@@ -0,0 +1,15 @@
+package main
+
+import "testing"
+
+func TestBarrier(t *testing.T) {
+	t.Run("Correct endpoints", func(t *testing.T) {
+		endpoints := []string{"http://httpbin.org/headers", "http://httpbin.org/User-Agent"}
+	})
+	t.Run("One endpoint incorrect", func(t *testing.T) {
+		endpoints := []string{"http://malformed-url", "http://httpbin.org/User-Agent"}
+	})
+	t.Run("Very Short Timeout", func(t *testing.T) {
+		endpoints := []string{"http://httpbin.org/headers", "http://httpbin.org/User-Agent"}
+	})
+}