RPOPLPUSH does about half of what's needed and BLPOP does the other half, but neither does the whole job.<p>It's not interesting to discuss what you <i>can</i> use to hack a queue together.  Lots and lots of really badly thought out queue services exist today built on top of memcached or a relational database or other things that appear to work in normal cases, but can go horribly wrong and start losing data when bad things happen.