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,
+	}
+}

internal/syncx/cached_resource_test.go

@@ -0,0 +1,66 @@
+package syncx
+
+import (
+	"context"
+	"math"
+	"sync"
+	"testing"
+	"time"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/cache/memory"
+	"forge.cadoles.com/cadoles/bouncer/internal/cache/ttl"
+	"github.com/pkg/errors"
+)
+
+func TestCachedResource(t *testing.T) {
+	refreshCalls := 0
+	cacheTTL := 1*time.Second + 500*time.Millisecond
+	duration := 2 * time.Second
+
+	expectedCalls := math.Ceil(float64(duration) / float64(cacheTTL))
+
+	resource := NewCachedResource(
+		ttl.NewCache(
+			memory.NewCache[string, string](),
+			memory.NewCache[string, time.Time](),
+			cacheTTL,
+		),
+		func(ctx context.Context, key string) (string, error) {
+			refreshCalls++
+			return "bar", nil
+		},
+	)
+
+	concurrents := 50
+	key := "foo"
+
+	var wg sync.WaitGroup
+
+	wg.Add(concurrents)
+
+	for i := range concurrents {
+		go func(i int) {
+			done := time.After(duration)
+
+			defer wg.Done()
+			for {
+				select {
+				case <-done:
+					return
+				default:
+					value, fresh, err := resource.Get(context.Background(), key)
+					if err != nil {
+						t.Errorf("%+v", errors.WithStack(err))
+					}
+					t.Logf("resource retrieved for goroutine #%d: (%s, %s, %v)", i, key, value, fresh)
+				}
+			}
+		}(i)
+	}
+
+	wg.Wait()
+
+	if e, g := int(expectedCalls), refreshCalls; e != g {
+		t.Errorf("refreshCalls: expected '%d', got '%d'", e, g)
+	}
+}