In ContainerLifecycleEventPreloader constructor, new ThreadGroup with hardcoded name is created each time the ContainerLifecycleEventPreloader instance is initialized. (The preloader can be initialized repeatedly for instance during application container reload.)

This creates a memory leak, although small in terms of memory, because created thread groups are never garbage collected. (There is a tree of created thread groups maintained in the ThreadGroup class which contains reference to every created group.)

    public ContainerLifecycleEventPreloader(int threadPoolSize, ObserverNotifier notifier) {
        this.executor = Executors.newFixedThreadPool(threadPoolSize,
                new DaemonThreadFactory(new ThreadGroup("weld-preloaders"), "weld-preloader-"));
        this.notifier = notifier;
    }

Can the created thread group instance be kept in a static field to avoid it being created repeatedly?