* Allow RateLimiter to change rate after construction.
* Check range of rate argument in constructor.
* Atomic increment for RateEstimator.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
We need to replace nanosleeps with condition variables so that we
can implement BeesContext::stop. Export the time calculation from
sleep_for() into a new method called sleep_time().
If the thread executing RateLimiter::sleep_for() is interrupted, it will
no longer be able to restart, as the sleep_time() method is destructive.
This calls for further refactoring of sleep_time() into destructive
and non-destructive parts; however, there are currently no users of
sleep_for() which rely on being able to restart after being interrupted
by a signal.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
update_monotonic does not reset the counter if a new count is smaller than
earlier counts. Useful when consuming an unsorted stream of eveent counts.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
RateEstimator estimates the rate of external events by sampling a
counter.
Conversion functions are provided to predict the time when the
event counter will be incremented to particular values based on past
observations of the event counter.
Synchronization functions are provided to block a thread until a specific
counter value is reached.
Event polling is supported using the history of previous event counts
to determine the predicted time of the next event. A decay function
emphasizes more recent event history.
Polling delays are bounded by minimum and maximum values in the constructor
parameters.
wait_for() and wait_until() block the calling thread until the target
event count is reached (or the counter is reset). These functions are
not bounded by min_delay or max_delay, and require a separate tread
to call update(). wait_for() waits for the counter to be incremented
from its current value by the given count. wait_until() waits for the
counter to reach an absolute value.
update() counts external events and unblocks threads that are blocked
in wait_for() or wait_until(). If the event counter decreases then it
is reset to the new value.
duration() and time_point() convert relative and absolute event counts
into relative and absolute C++11 time quantities based on the last update
time, last observed event count, and the observed event rate.
Convenience functions seconds_for() and seconds_until() calculate
polling delays for for the desired relative and absolute event counts
respectively. These delays are bounded by max and min delay parameters.
rate() and ratio() provide conversion factors based on the current
estimated event rate.
Signed-off-by: Zygo Blaxell <bees@furryterror.org>
