Shared connection

In many environment, the latency between client and db is too high, to get better performance client need spawn more connections to cope with latency，but this may lead to contention problems.

Put a proxy (mxs) between client and db, let proxy more closer to db(latency between proxy and db should be much more lower than latency between client and proxy), let multiple client connections share the same backend connection in order to reduce the contention;

if can keep session state (session variables, temproary table, transaction ...) consistant will be better;