Guys, I think we should provide user with ability to validate cache topology before each cache operation.
Now user cannot validate the topology of cache update, but this seems to be a good feature. I can validate task topology and throw exception on MAP step, but I cannot do that on cache put. I suggest introducing special topology validator. Whenever cache topology changes - it is passed to validator. Validator can check nodes number and presence of particular (if user have servers with special role in topology), this also may be used to validate segment local node operates in. If cache topology is not valid each cache update throws exception until cache topology does not become valid back. --Yakov
