...

There will be no impact on existing users.

Rejected Alternatives

Introducing a second poll argument

An alternative way of limitting the number of messages would be to introduce a second argument to poll(), which controls the maximum number of records which will be returned. It would have the following advantages:

...

It should also be mentioned that introducing a configuration parameter will not hinder us from introducing a second parameter to poll() in the future.

Adding a KafkaConsumer#heartbeat()/ping() method

See http://mail-archives.apache.org/mod_mbox/kafka-users/201512.mbox/%3CCAJDuW=Auq8bM7JVaDmEBMmJscTZ812+F4rP_Wkwa6mR6JmMMHw@mail.gmail.com%3E.