Fix: S3 wrap PutObject into ReadSeeker

Author: obs-gh-justindaines

pkg/handler/forwarder/handler.go

@@ -109,10 +109,28 @@ func (h *Handler) WriteSQS(ctx context.Context, r io.Reader) error {
 		key = strings.Trim(h.DestinationURI.Path, "/") + "/" + key
 	}
 
+	// Convert to seekable reader to allow AWS SDK to retry S3 PutObject operations
+	// by rewinding the stream. If the reader is already a bytes.Buffer, convert it
+	// directly to bytes.Reader to avoid an extra copy.
+	var body io.ReadSeeker
+	if r != nil {
+		// Check if r is a *bytes.Buffer to avoid unnecessary copy
+		if buf, ok := r.(*bytes.Buffer); ok {
+			body = bytes.NewReader(buf.Bytes())
+		} else {
+			// For other io.Reader types, read into memory
+			data, err := io.ReadAll(r)
+			if err != nil {
+				return fmt.Errorf("failed to read message data: %w", err)
+			}
+			body = bytes.NewReader(data)
+		}
+	}
+
 	_, err = h.S3Client.PutObject(ctx, &s3.PutObjectInput{
 		Bucket:      aws.String(h.DestinationURI.Host),
 		Key:         &key,
-		Body:        r,
+		Body:        body,
 		ContentType: aws.String("application/x-aws-sqs"),
 	})
 	if err != nil {