feat: prevent call bursts on oidc provider refresh

internal/syncx/cached_resource.go

@@ -0,0 +1,63 @@
+package syncx
+
+import (
+	"context"
+	"sync"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/cache"
+	"github.com/pkg/errors"
+)
+
+type RefreshFunc[K comparable, V any] func(ctx context.Context, key K) (V, error)
+
+type CachedResource[K comparable, V any] struct {
+	cache   cache.Cache[K, V]
+	lock    sync.RWMutex
+	refresh RefreshFunc[K, V]
+}
+
+func (r *CachedResource[K, V]) Clear() {
+	r.cache.Clear()
+}
+
+func (r *CachedResource[K, V]) Get(ctx context.Context, key K) (V, bool, error) {
+	value, exists := r.cache.Get(key)
+	if exists {
+		return value, false, nil
+	}
+
+	locked := r.lock.TryLock()
+	if !locked {
+		r.lock.RLock()
+
+		value, exists := r.cache.Get(key)
+		if exists {
+			r.lock.RUnlock()
+			return value, false, nil
+		}
+
+		r.lock.RUnlock()
+	}
+
+	if !locked {
+		r.lock.Lock()
+	}
+
+	defer r.lock.Unlock()
+
+	value, err := r.refresh(ctx, key)
+	if err != nil {
+		return *new(V), false, errors.WithStack(err)
+	}
+
+	r.cache.Set(key, value)
+
+	return value, true, nil
+}
+
+func NewCachedResource[K comparable, V any](cache cache.Cache[K, V], refresh RefreshFunc[K, V]) *CachedResource[K, V] {
+	return &CachedResource[K, V]{
+		cache:   cache,
+		refresh: refresh,
+	}
+}