private void process(final FetchCommittedOffsetsEvent event) {
        if (!requestManagers.commitRequestManager.isPresent()) {
            event.future().completeExceptionally(new KafkaException("Unable to fetch committed " +
                    "offset because the CommittedRequestManager is not available. Check if group.id was set correctly"));
            return;
        }
        CommitRequestManager manager = requestManagers.commitRequestManager.get();
        CompletableFuture<Map<TopicPartition, OffsetAndMetadata>> future = manager.fetchOffsets(event.partitions(), event.deadlineMs());
        future.whenComplete(complete(event.future()));
    }
An {@link EventProcessor} that is created and executes in the {@link ConsumerNetworkThread network thread}
which processes {@link ApplicationEvent application events} generated by the application thread.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/events/ApplicationEventProcessor.java