In our operations, we make heavy use of replace_address (or replace_address_first_boot) in order to replace broken nodes. We now realize that writes are not sent to the replacement nodes while they are in hibernate state and streaming in data. This runs counter to what our expectations were, especially since we know that writes ARE sent to nodes when they are bootstrapped into the ring.
It seems like cassandra should arrange to send writes to a node that is in the process of replacing another node, just like it does for a nodes that are bootstraping. I hesitate to phrase this as "we should send writes to a node in hibernate" because the concept of hibernate may be useful in other contexts, as per
CASSANDRA-8336. Maybe a new state is needed here?
Among other things, the fact that we don't get writes during this period makes subsequent repairs more expensive, proportional to the number of writes that we miss (and depending on the amount of data that needs to be streamed during replacement and the time it may take to rebuild secondary indexes, we could miss many many hours worth of writes). It also leaves us more exposed to consistency violations.