CallbackHandler in Kafka 0.8

Hello-

Is CallbackHandler supported in Kafka 0.8 for async producers?

If yes, can I use it to alter the batched messages before they are pushed
to broker? For example, I may want to delete some of the messages in the
batch based on some business logic in my application?

If no, is there any alternate way? I want to do some kind of single
instancing on messages pushed in kafka in last X minutes.

thanks