We used a new kind of virtual connection that, just like with cluster, groups
multiple connection objects and handles the logic needed to switch among them
depending on the kind of operation performed by commands..
Our default implementation starts by picking up a random slave and switches to
the master as soon as a command performing a write operation against a key is
detected. The master server will then be used for all the subsequent requests
unless a manual switch to a different connection object is performed.
Redis transactions are always performed on the master server, which means that
the switch to master is done as soon as the client issues a WATCH, MULTI or
any other command related to transactions.
See also https://github.com/nrk/predis/issues/21 for more details.
Daniele Alessandri