The recommendations here are under development and may change before implementation.
The intent of the REPLICA READ (also known as CMD_GET_REPLICA in the server) operation is to allow a client to perform retrieval operations only against one or more replicas. This would be an inconsistent read. While it could be used for nearly any purpose, the only common use case is expected to be in the event of failures when a known inconsistent read is okay.
res = nil
is_replica_read = false
res = cbc.get("foo")
rescue Couchbase::Error::Timeout => ex
res = cbc.get("foo", :replica => true)
is_replica_read = true
# do something useful
These recommendations are preliminary, and have not been reviewed.
The replica read command is intentionally simple. It would attempt to iterate through all of the replicas as designated by the configuration supplied by the cluster in order, trying to get the specified key.
REPLICA READ is a binary protocol only operation. It could be implemented in ASCII, but that would require changes in moxi and additional clients.