public void addListener(RequestFutureListener<T> listener) {
        this.listeners.add(listener);
        if (failed())
            fireFailure();
        else if (succeeded())
            fireSuccess();
    }
Add a listener which will be notified when the future completes
@param listener non-null listener to add
clients/src/main/java/org/apache/kafka/clients/consumer/internals/RequestFuture.java