#4 Configuration of backing off strategy

[Andrew McMillan]

At the moment DBBalancer appears to take a fairly
simplistic approach to attempting to get a back-end
connection when a client connects to it.

In the event that all back-end connections are in use,
it would be reasonable to put the request into a queue,
holding it in abeyance for a [configurable] period of
time before finally giving up and returning the
connection failure to the client.

With web applications this is especially useful because
most connections are very short-lived (usually well
under 1 second). This would mean that a maximum queue
wait time of (say) 700 - 1500 mS would allow a very
busy system to gain considerable benefit in smoothing
peak load.

Hand in hand with this, it would be good to get
statistics of connections handled / connections queued
/ connections dropped dumped to syslog every
[configurable] seconds. These statistics would enable
the system admin to tune the numbers of client and
server connections.