feat: retry mechanism with exponential backoff

internal/retry/retry.go

@@ -0,0 +1,45 @@
+package retry
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+)
+
+type Retrier struct {
+	maxRetries int
+	backoff    []time.Duration
+}
+
+func NewRetrier(maxRetries int, backoff []time.Duration) *Retrier {
+	return &Retrier{maxRetries: maxRetries, backoff: backoff}
+}
+
+// DefaultRetrier returns a retrier with 3 attempts, exponential backoff: 1s, 5s, 30s.
+func DefaultRetrier() *Retrier {
+	return NewRetrier(3, []time.Duration{1 * time.Second, 5 * time.Second, 30 * time.Second})
+}
+
+func (r *Retrier) Do(ctx context.Context, fn func() error) error {
+	var lastErr error
+	for attempt := 0; attempt <= r.maxRetries; attempt++ {
+		if attempt > 0 {
+			delay := r.backoff[attempt-1]
+			slog.Info("retrying", "attempt", attempt, "delay", delay)
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(delay):
+			}
+		}
+
+		err := fn()
+		if err == nil {
+			return nil
+		}
+		lastErr = err
+		slog.Warn("attempt failed", "attempt", attempt, "error", err)
+	}
+	return fmt.Errorf("all %d attempts failed, last error: %w", r.maxRetries+1, lastErr)
+}