public void add(CompletableEvent<?> event) {
        tracked.add(Objects.requireNonNull(event, "Event to track must be non-null"));
    }
Adds a new {@link CompletableEvent event} to track for later completion/expiration.

@param event Event to track
clients/src/main/java/org/apache/kafka/clients/consumer/internals/events/CompletableEventReaper.java