Module Async_kernel.Synchronous_time_source

id t returns a unique, consistent identifier which can be used e.g. as a map or hash table key.

length t returns the number of alarms in the underlying Timing_wheel.

create ~now () creates a new time source. The default timing_wheel_config has 100 microsecond precision, with levels of >1s, >1m, >1h, >1d. The timing_wheel_config is used to tune performance; configuration does not affect the fact that alarms fire in non-decreasing time order.

is_wall_clock reports whether this time source represents 'wall clock' time, or some alternate source of time.

The behavior of now is special for wall_clock (); it always calls Time_ns.now (), so it can return times that the time source has not yet been advanced to.

Removes the special behavior of now for wall_clock (); it always returns the timing wheel's notion of now, which means that the following inequality always holds: timing_wheel_now () <= now ().

advance_by_alarms t ~to_ advances t's time to to_, running callbacks for all alarms in t whose at <= to_. Callbacks run in nondecreasing order of at. If to_ <= now t, then now t does not change (and in particular does not go backward), but alarms with at <= to_ may still may fire.

Instead of advance_directly, you probably should use advance_by_alarms. advance_directly t ~to_ advances the clock directly to to_, whereas advance_by_alarms advances the clock in steps, to each intervening alarm. In particular periodic/rearming timers will fire at most twice.

run_at t at f schedules an alarm that will run f during the next subsequent advance_by_alarms t ~to_ that causes now t >= at. If at <= now t, then f will to run at the next call to advance_by_alarms. f is allowed to do all Synchronous_time_source operations except for advance_by_alarms (because f is already running during advance_by_alarms. Adding alarms is not zero-alloc and the underlying events live in the OCaml heap.

run_after t span f is run_at t (now t + span) f.

run_at_intervals t span f causes f to run at intervals now t + k * span, for k = 0, 1, 2, etc. run_at_intervals raises if span < alarm_precision t.

max_allowed_alarm_time t returns the greatest at that can be supplied to add. max_allowed_alarm_time is not constant; its value increases as now t increases.

A time source with now t given by wall-clock time (i.e. Time_ns.now), and automatically advanced at the start of each Async cycle. The wall clock uses the same timing wheel as that used by the Async scheduler, and is hence similarly affected by the ASYNC_CONFIG environment variable.