This will mean the leader will write the record to its local
log but will respond without awaiting full acknowledgement
from all followers.
In this case should the leader fail immediately after acknowledging
the record but before the followers have replicated it then the
record will be lost.
This means the leader will wait for the
full set of in-sync replicas to acknowledge the record.
This guarantees that the record will not be lost as long as
at least one in-sync replica remains alive. This is the strongest
If set to zero then the producer will not wait
for any acknowledgment from the server at all.
The record will be immediately added to the socket buffer and
considered sent. No guarantee can be made that the server has received
the record in this case, and the retries configuration will not
take effect (as the client won't generally know of any failures).
The offset given back for each record will always be set to -1.