A gen_server wrapper with precise ticks
Copyright (c) 2016 Guilherme Andrade
Version: 2.0.1
Authors: Guilherme Andrade (erlchronos(at)gandrade(dot)net
gandrade(dot)net)).
erlchronos
: Erlang/OTP gen_server wrapper with ticks
erlchronos
provides a gen_server
wrapper, ticked_gen_server
,
that allows one to more easily manage triggering and dealing with ticks at regular intervals by specifying two new callbacks,tick_duration/2
and handle_tick/4
.
It also does away with the usual erlang:send_after/3
,timer:send_interval/2
, etc. approaches, instead relying
on two key mechanisms for tick enforcement:
gen_server
‘s support for specifying timeout values on callbacks - which takes care of idle-inbox periods;The traditional approach of having a message sent to a gen_server
‘s inbox at regular intervals isn’t always
the more appropriate, and might misbehave significantly every time the system is subjected to message bursts (among other factors), even when actively accounting for drift, due to the strictly-ordered nature of inbox consumption.
An alternative would be to change the receive
logic itself and pattern-match against timer / higher-priority messages, but this would quickly degrade performance on flooded inboxes and create a degeneration feedback loop.
This compromise solution tries not to fiddle too much with, nor reinvent the existing building blocks.
tick_duration/2
callback can be used to easily lower tick rate;init
/ handle_call
/ handle_cast
/ handle_info
return values;handle_info
) made only of the ‘timeout’ atom.start
/start_link
option:
ticked_gen_server:start(?MODULE, [], [{ticks, ["tick identifier"]}]).
ticked_gen_server
behaviour, which includes two extra callbacks:
% TickDuration in milliseconds
-spec tick_duration(TickId :: term(), State :: term())
-> {TickDuration :: pos_integer(), NewState :: term()}.
tick_duration("tick identifier", State) ->
{100, State}.
-spec handle_tick(TickId :: term(), TickGeneration :: non_neg_integer(),
ActualTickDuration :: non_neg_integer(), State :: term())
-> {noreply, NewState :: term()}.
handle_tick(TickId, TickGeneration, ActualTickDuration, State) ->
% Tick!
{noreply, State};
Basic example under examples/.
ticked_gen_server
to gain some insight into predicted execution times and, based on this knowledge, preemptively sacrifice execution capacity (by sleeping) and trade it for a lower likelihood of jitter;gen_fsm
/ gen_event
in a similar fashion.erlchronos |
ticked_gen_server |