1 files changed, 63 insertions, 0 deletions
diff --git a/modules/queue/backoff.go b/modules/queue/backoff.go
new file mode 100644
index 0000000..cda7233
--- /dev/null
+++ b/modules/queue/backoff.go
@@ -0,0 +1,63 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package queue
+
+import (
+	"context"
+	"time"
+)
+
+const (
+	backoffBegin = 50 * time.Millisecond
+	backoffUpper = 2 * time.Second
+)
+
+type (
+	backoffFuncRetErr[T any] func() (retry bool, ret T, err error)
+	backoffFuncErr           func() (retry bool, err error)
+)
+
+func backoffRetErr[T any](ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncRetErr[T]) (ret T, err error) {
+	d := begin
+	for {
+		// check whether the context has been cancelled or has reached the deadline, return early
+		select {
+		case <-ctx.Done():
+			return ret, ctx.Err()
+		case <-end:
+			return ret, context.DeadlineExceeded
+		default:
+		}
+
+		// call the target function
+		retry, ret, err := fn()
+		if err != nil {
+			return ret, err
+		}
+		if !retry {
+			return ret, nil
+		}
+
+		// wait for a while before retrying, and also respect the context & deadline
+		select {
+		case <-ctx.Done():
+			return ret, ctx.Err()
+		case <-time.After(d):
+			d *= 2
+			if d > upper {
+				d = upper
+			}
+		case <-end:
+			return ret, context.DeadlineExceeded
+		}
+	}
+}
+
+func backoffErr(ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncErr) error {
+	_, err := backoffRetErr(ctx, begin, upper, end, func() (retry bool, ret any, err error) {
+		retry, err = fn()
+		return retry, nil, err
+	})
+	return err
+}