The check of sent requests and containers is done unconditionally
every second even though the request timeout is 10 seconds and the
container timeout is 600 seconds. This commit uses fine grained timers
instead in order to avoid useless system wake-up events.
The check of sent requests is now scheduled on demand when a new
request is queued. Then the callback, while parsing queued requests,
computes the delta to the closest expiring request and automatically
schedules the next check if necessary.
Given the high value of the container timeout, its callback is called
repeatedly every 600 seconds, unless it computes a lower delta for an
expiring container using the same logic as for the requests.
06618a5253