report retry progress

internal/playback/supervisor.go

@@ -27,6 +27,7 @@ func runWithRetry(
 	attempt attemptFunc,
 	shouldRetry retryDecider,
 	wait waitFunc,
+	observer retryObserver,
 ) error {
 	failedAttempts := 0
 
@@ -40,11 +41,29 @@ func runWithRetry(
 		}
 
 		failedAttempts++
-		if !shouldRetry(err) || !policy.canRetry(failedAttempts) {
+		willRetry := shouldRetry(err) && policy.canRetry(failedAttempts)
+		if !willRetry {
+			if observer != nil {
+				observer(retryEvent{
+					FailedAttempts: failedAttempts,
+					Err:            err,
+					WillRetry:      false,
+				})
+			}
 			return err
 		}
 
-		if err := wait(ctx, policy.retryDelay(failedAttempts)); err != nil {
+		delay := policy.retryDelay(failedAttempts)
+		if observer != nil {
+			observer(retryEvent{
+				FailedAttempts: failedAttempts,
+				Err:            err,
+				RetryIn:        delay,
+				WillRetry:      true,
+			})
+		}
+
+		if err := wait(ctx, delay); err != nil {
 			if ctx.Err() != nil {
 				return ctx.Err()
 			}
@@ -52,3 +71,12 @@ func runWithRetry(
 		}
 	}
 }
+
+type retryEvent struct {
+	FailedAttempts int
+	Err            error
+	RetryIn        time.Duration
+	WillRetry      bool
+}
+
+type retryObserver func(retryEvent)