fix: close slow event subscribers safely

server/api/service_test.go

@@ -257,6 +257,27 @@ func readServerWebSocketFrame(reader *bufio.Reader) ([]byte, error) {
 	return payload, err
 }
 
+func TestEventHubClosesSlowSubscribersExactlyOnce(t *testing.T) {
+	hub := newEventHub()
+	subscriber := hub.subscribe("player-1")
+	event := ControlPlaneEvent{Event: "state_changed", Revision: 1, ResourceID: "ticket-1234567890123456", OccurredAt: time.Unix(1000, 0).UTC(), State: "QUEUED", PlayerID: "player-1"}
+	for i := 0; i < eventQueueCapacity; i++ {
+		if err := hub.publish(event); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := hub.publish(event); err != nil {
+		t.Fatal(err)
+	}
+	for {
+		_, open := <-subscriber.queue
+		if !open {
+			break
+		}
+	}
+	hub.unsubscribe(subscriber)
+}
+
 func TestQueueAPIRejectsUnauthenticatedUnknownAndOversizedInput(t *testing.T) {
 	service := &Service{Sessions: domain.NewSessionStore(), Queue: domain.NewQueue(), Candidate: func(string, string) (domain.Candidate, error) { return domain.Candidate{}, nil }}
 	server := httptest.NewServer(service.Handler())