
Balancing vs Stickiness

  Balancing:
    random
    shuffle
    roundRobin
    leastConns

  Sticky:
    per USER
    per HOST

Work on implementing just the balancing strategies, for now.

Note: The state files used for the balancing strategies, especially once
health checks are added, could be externally cached/managed, e.g. via
memcache/redis, using JSON.

  Issues there: if each mod_proxy is doing its own health checks of the
  servers, it's possible for individual mod_proxy instances to disagree
  about the health of a given backend (think split-brain syndrome).

  When each mod_proxy instance is managing its own view, this is OK;
  when they all share that persisted view, it could be a problem.
