add retry for http send in case of failure

transport/http/http.go

@@ -4,8 +4,11 @@ import (
 	"bytes"
 	"encoding/json"
 	"flag"
+	"fmt"
+	"math"
 	"net/http"
 	"sync"
+	"time"
 
 	"github.com/netsampler/goflow2/v2/transport"
 )
@@ -54,23 +57,40 @@ func (d *HTTPDriver) Send(key, data []byte) error {
 			return err
 		}
 
-		req, err := http.NewRequest("POST", d.httpDestination, bytes.NewBuffer(jsonData))
-		if err != nil {
-			return err
+		maxRetries := 3
+		delay := time.Millisecond * 500 // initial delay
+		for i := 0; i < maxRetries; i++ {
+			req, err := http.NewRequest("POST", d.httpDestination, bytes.NewBuffer(jsonData))
+			if err != nil {
+				return err
+			}
+
+			req.Header.Set("Content-Type", "application/json")
+			req.Header.Set(d.httpAuthHeader, d.httpAuthCredentials)
+
+			client := &http.Client{}
+			resp, err := client.Do(req)
+			if err != nil {
+				if i == maxRetries-1 {
+					return err
+				}
+				continue
+			}
+			defer resp.Body.Close()
+
+			// If the status code is not in the 2xx range, retry
+			if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+				if i == maxRetries-1 {
+					return fmt.Errorf("failed to send data, status code: %d", resp.StatusCode)
+				}
+				time.Sleep(delay * time.Duration(math.Pow(2, float64(i)))) // exponential backoff
+				continue
+			}
+
+			// reset batchData
+			d.batchData = d.batchData[:0]
+			break
 		}
-
-		req.Header.Set("Content-Type", "application/json")
-		req.Header.Set(d.httpAuthHeader, d.httpAuthCredentials)
-
-		client := &http.Client{}
-		resp, err := client.Do(req)
-		if err != nil {
-			return err
-		}
-		defer resp.Body.Close()
-
-		// reset batchData
-		d.batchData = d.batchData[:0]
 	}
 
 	return nil