Update retry proxy to include a recursive constructor

hack/failonceserver/main.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"io"
 	"net/http"
+	"os"
 	"sync"
 )
 
@@ -10,7 +12,9 @@ func main() {
 	var mtx sync.RWMutex
 	paths := map[string]bool{}
 
-	http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	http.ListenAndServe(":8082", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		io.Copy(os.Stdout, r.Body)
+
 		mtx.RLock()
 		shouldSucceed := paths[r.URL.Path]
 		mtx.RUnlock()

hack/retryproxy/main.go

@@ -18,32 +18,9 @@ func main() {
 		}
 		r.Body.Close()
 
-		// go run ./hack/failserver
-		first := newReverseProxy("http://localhost:8081")
-
-		first.ModifyResponse = func(r *http.Response) error {
-			if r.StatusCode == http.StatusServiceUnavailable {
-				// Returning an error will trigger the ErrorHandler.
-				return errRetry
-			}
-			return nil
-		}
-
-		first.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
-			if err == errRetry {
-				log.Println("retrying")
-
-				// Simulate calling the next backend.
-				// go run ./hack/successserver
-				next := newReverseProxy("http://localhost:8082")
-				next.ServeHTTP(w, newReq(r, body))
-				return
-			}
-		}
-
-		log.Println("serving")
-		first.ServeHTTP(w, newReq(r, body))
+		backend(r, body, 0).ServeHTTP(w, newReq(r, body))
 	}))
+
 }
 
 var errRetry = errors.New("retry")
@@ -54,8 +31,49 @@ func newReq(r *http.Request, body []byte) *http.Request {
 	return clone
 }
 
-func newReverseProxy(addr string) *httputil.ReverseProxy {
-	u, err := url.Parse(addr)
+type backends struct {
+	attempt     int
+	requestBody []byte
+}
+
+func backend(r *http.Request, body []byte, attempt int) http.Handler {
+	// go run ./hack/failserver
+	first := newReverseProxy(getEndpoint(attempt))
+
+	first.ModifyResponse = func(r *http.Response) error {
+		if r.StatusCode == http.StatusServiceUnavailable {
+			// Returning an error will trigger the ErrorHandler.
+			return errRetry
+		}
+		return nil
+	}
+
+	first.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
+		if err == errRetry {
+			log.Println("retrying")
+
+			// Simulate calling the next backend.
+			// go run ./hack/successserver
+			backend(r, body, attempt+1).ServeHTTP(w, newReq(r, body))
+			return
+		}
+	}
+
+	log.Println("serving")
+	return first
+}
+
+func getEndpoint(attempt int) string {
+	switch attempt {
+	case 0:
+		return "http://localhost:8081"
+	default:
+		return "http://localhost:8082"
+	}
+}
+
+func newReverseProxy(host string) *httputil.ReverseProxy {
+	u, err := url.Parse(host)
 	if err != nil {
 		panic(err)
 	}