I'm assuming this is somewhat related to your previous question on cross-DC replication. This is not an ideal set up as mentioned there. If the replica lags then it will fall out of the "in-sync-replica" set. You could tune parameters that effectively allow a high (but bounded over time) lag between the replica and the leader. There is no buffer per se - the replicas just keep fetching from the leader (which would have appended the messages to its log).
If your producer has acks set to -1 (which means wait until all replicas in ISR have received the message) it would slow down your producer considerably. (You could use acks = 1 in that case though but with weaker guarantees - i.e., your message could be lost in failure scenarios). Joel On Fri, Jun 28, 2013 at 5:41 PM, Yu, Libo <libo...@citi.com> wrote: > Hi, > > Assume A and B are two brokers in a kafka server. And there is long network > Latency between A and B. For a partition with two replications, one > replication > Is assigned to A and the other is assigned to B. Number of acknowledge is set > to one. Assume the partition is handled by broker A. > > After a message is accepted and saved by A, ack will be sent and the message > will be sent to broker B at the same time. But due to long network latency > between > A and B, it is possible that B lags behind A. In this case, is there a buffer > on broker A > that holds all messages to be written to B? Is there any limit on the lag > between A > and B? > > Compare with the case when there is no network latency between A and B, any > difference in publishing speed? > > Thanks > > Libo >
