Hi, I have a running Zookeeper (3.5) cluster where the machines need to be replaced. I was thinking of just setting the same ID on each new machine, and then doing a rolling replacement: take down old ID 1, start new ID 1, let it rejoin the cluster and replicate the state, then continue with the other replicas.
I'm finding conflicting information on the internet about the safety of this. The Apache Kafka FAQ says to do exactly this when replacing a failed Zookeeper replica, and the new machine will just replicate the state before participating in the quorum. Other places on the internet say that reusing the ID without also copying over the state directory will break assumptions that ZAB makes about replicas, with bad (but nondescript) consequences. So, is it safe to reuse IDs in the way I described? If not, what's the suggested procedure for a rolling replacement of all cluster replicas? Thanks, - Dave
