Interface NackHandler (1.4.12)

A NackHandler handles when nack() is called in a user's AckReplyConsumer. Pub/Sub Lite does not have a concept of 'nack'. When nack() is called in an AckReplyConsumerr, nack(message) is called with the nacked message.

If the returned future is successful, the message is acknowledged. If the future fails, the subscriber client will be failed. The default behavior is to immediately fail the client.