About Administration for upgrading redis instance

[Xinyu Zhang]

Hi all,

I have one question about the "Upgrading or restarting a Redis instance without downtime" section in http://redis.io/topics/admin.

Following the steps in that article, let's say if A is current instance and we use B as the slave. The clients are writing to A and will change to write to B when "slave-read-only" of B is set to "no".

My question is, if a client calls "SET x 1" when it writes to A and calls "SET x 2" when it changes to write to B, it seems that there is no guarantee of the final value of "x". The expected result is 2, but for B, we are not sure whether the command "SET x 1" from A arrives earlier or later than the command "SET x 2" from the client. So it is also possible that the value of "x" is 1.

Any comments are appreciated.

Thanks and regards,

Xinyu