ack, go back to Broadway.Acknowledger module for more information.
ack( ack_ref :: term(), successful :: [Broadway.Message.t()], failed :: [Broadway.Message.t()] ) :: :ok
Invoked to acknowledge successful and failed messages.
ack_refis a term that uniquely identifies how messages should be grouped and sent for acknowledgement. Imagine you have a scenario where messages are coming from different producers. Broadway will use this information to correctly identify the acknowledger and pass it among with the messages so you can properly communicate with the source of the data for acknowledgement.
successfulis the list of messages that were successfully processed and published.
failedis the list of messages that, for some reason, could not be processed or published.