public void add(final ApplicationEvent event) {
        Objects.requireNonNull(event, "ApplicationEvent provided to add must be non-null");
        applicationEventQueue.add(event);
        wakeupNetworkThread();
    }
Add an {@link ApplicationEvent} to the handler and then internally invoke {@link #wakeupNetworkThread()}
to alert the network I/O thread that it has something to process.

@param event An {@link ApplicationEvent} created by the application thread
clients/src/main/java/org/apache/kafka/clients/consumer/internals/events/ApplicationEventHandler.java