util: add retry mechanism

Author: wuriyanto48

util/retry.go

@@ -0,0 +1,110 @@
+package util
+
+import (
+	"context"
+	"time"
+)
+
+// RetryFunc is a function type that will try to be called again if it doesn't work
+type RetryFunc func() bool
+
+// RetryCallbackFunc is a function type for callback
+type RetryCallbackFunc func()
+
+// Retry is a wrapper function that is used to try to call external resources that have the potential to fail
+func Retry(ctx context.Context, n int, interval time.Duration,
+	done chan<- bool, f RetryFunc, onSucceed RetryCallbackFunc, onError RetryCallbackFunc) {
+	var i int = 1
+	go func(ctx context.Context, i int, n int, interval time.Duration,
+		done chan<- bool, f RetryFunc, onSucceed RetryCallbackFunc, onError RetryCallbackFunc) {
+
+		for {
+			select {
+			case <-ctx.Done():
+				done <- true
+				return
+			default:
+			}
+
+			succeed := f()
+			if succeed {
+				done <- true
+
+				if onSucceed != nil {
+					onSucceed()
+				}
+				return
+			}
+
+			if i == n {
+				done <- true
+
+				if onError != nil {
+					onError()
+				}
+				return
+			}
+
+			<-time.After(interval)
+
+			i++
+
+		}
+	}(ctx, i, n, interval, done, f, onSucceed, onError)
+}
+
+// Usage
+
+// func main() {
+// 	f := func() bool {
+// 		resp, err := httpPost("not_ok")
+// 		if err != nil {
+// 			fmt.Println(err)
+// 			return true
+// 		}
+
+// 		statusOK := resp.httpCode >= 200 && resp.httpCode < 300
+// 		if !statusOK {
+// 			fmt.Println("retry")
+// 			return false
+// 		}
+
+// 		return true
+// 	}
+
+// 	done := make(chan bool, 1)
+
+// 	ctx, cancel := context.WithCancel(context.Background())
+// 	//ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*500)
+// 	defer func() { cancel() }()
+
+// 	onSucceed := func() {
+// 		fmt.Println("execution succeed")
+// 	}
+
+// 	onError := func() {
+// 		fmt.Println("execution error")
+// 	}
+
+// 	Retry(ctx, 5, 3*time.Second, done, f, onSucceed, onError)
+
+// 	<-done
+
+// 	//time.Sleep(time.Second * 15)
+// }
+
+// type response struct {
+// 	httpCode int
+// }
+
+// func httpPost(data string) (*response, error) {
+// 	if data == "fatal" {
+// 		return nil, errors.New("fatal error")
+// 	}
+
+// 	if data == "not_ok" {
+// 		return &response{httpCode: 400}, nil
+// 	}
+
+// 	return &response{httpCode: 200}, nil
+// }