R58: idempotent RefreshCoordinator Shutdown; no close-close

refresh_coordinator.go

@@ -37,6 +37,11 @@ type RefreshCoordinator struct {
 	stopChan               chan struct{}
 	config                 RefreshCoordinatorConfig
 	wg                     sync.WaitGroup
+	// shutdownOnce makes Shutdown idempotent: close(rc.stopChan) on an
+	// already-closed channel would panic ('close of closed channel').
+	// Repeated setup/teardown (e.g. Traefik plugin reload) can close the
+	// same Authenticator -> same coordinator more than once.
+	shutdownOnce sync.Once
 }
 
 // RefreshCoordinatorConfig configures the refresh coordinator behavior
@@ -720,8 +725,10 @@ func (rc *RefreshCoordinator) GetMetrics() map[string]interface{} {
 // (one map LoadAndDelete) and harmless after Shutdown — sync.Map operations
 // remain safe on an unused coordinator until GC.
 func (rc *RefreshCoordinator) Shutdown() {
-	close(rc.stopChan)
-	rc.wg.Wait()
+	rc.shutdownOnce.Do(func() {
+		close(rc.stopChan)
+		rc.wg.Wait()
+	})
 }
 
 // AllowRequest reports whether the circuit breaker allows a request. Lock-free.

review_r58_shutdown_test.go

@@ -0,0 +1,31 @@
+package traefikoidc
+
+import (
+	"testing"
+	"time"
+)
+
+// TestRefreshCoordinatorShutdownIdempotent guards against a panic when the
+// coordinator is shut down more than once. Close() on the same
+// Authenticator can be reached via both the plugin-context cancellation hook
+// (main.go) and the resource-manager teardown path, so RefreshCoordinator
+// Shutdown must tolerate repeated calls — the previous close(rc.stopChan)
+// panicked with 'close of closed channel' on the second call.
+func TestRefreshCoordinatorShutdownIdempotent(t *testing.T) {
+	rc := NewRefreshCoordinator(DefaultRefreshCoordinatorConfig(), NewLogger(DefaultLogLevel))
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatalf("second Shutdown panicked: %v", r)
+		}
+	}()
+	rc.Shutdown()
+	rc.Shutdown()
+}
+
+// Ensure cleanup goroutine is running before shutdown completes so the
+// shutdown path is actually exercised (stopChan close) and wg drained.
+func TestRefreshCoordinatorShutdownStopsCleanup(t *testing.T) {
+	rc := NewRefreshCoordinator(DefaultRefreshCoordinatorConfig(), NewLogger(DefaultLogLevel))
+	time.Sleep(50 * time.Millisecond)
+	rc.Shutdown()
+}