We are using Couchbase 4.0.0 only as a key/value store. We have a single key that gets accessed almost every request (I know we need to fix this) so we see a single server getting the vast majority of gets. Then later on we see that server’s stat get up to 1K gets/sec and drop down to near 0 without any change to the performance or functionality of our application. That key is still getting accessed just as frequently and the couchbase web dashboard still shows it at the top of the list by an order of magnitude. Does Couchbase replicate this key to other nodes (beyond our setting of 1 for backups) once a node sees 1k gets/sec and use those replicas for serving the key? If so, I can’t find any docs on this functionality nor does it make sense based on my understanding of how Couchbase works
No, a given key is only ever “active” on a single node, so all requests for that key will be serviced by a single node[*].
(There is an exception to this - you can use the replica read API to explicitly ask to read a key from a replica, but this is a different operation and only normally used in advanced use-cases where a node is down and the application has explicitly decided to forgo consistency and read (a potentially out-of-date) value from a replica.)
OK, thank you for confirming that. I think there must be a problem with the Zenoss Couchbase plugin we are using.