/**
     * Publishes an event to all instances.
     *
     * @param eventName the event name.
     * @param data optional event data.
     */
    public void publishEvent(final String eventName, final String data) {
        publishEvent(eventName, TARGET_ALL, data);
    }

    /**
     * Publishes an event to a specific instance or all instances.
     *
     * @param eventName the event name.