- Two clusters: A & B
- Both are two DC cluster
- Both use GossipingPropertyFileSnitch with different listen_address/broadcast_address
A new node was added to cluster A with a broadcast_address of an existing node in cluster B (due to an out of data DNS entry). Cluster B added all of the nodes from cluster A, somehow bypassing the cluster name mismatch check for this nodes. The first reference to cluster A nodes in cluster B logs is when then were added:
Cluster B nodes then tried to gossip to cluster A nodes, but cluster A kept them out with 'ClusterName mismatch'. Cluster B however tried to send to send reads/writes to cluster A and general mayhem ensued.
Obviously this is a Bad (TM) config that Should Not Be Done. However, since the consequence of crazy merged clusters are really bad (the reason there is the name mismatch check in the first place) I think the hole is reasonable to plug. I'm not sure exactly what the code path is that skips the check in GossipDigestSynVerbHandler.