Time
A Brief History
ChronoTrigger was originally conceived as a solution to what I saw as a strange blind-spot in Ruby: you can't easily make an accurate world clock that will count seconds at the exact same time as, for example, an atomic clock.
It seems like this should be trivially easy, and in some languages it is. Ruby can sleep, but this is really just an offset from whatever arbitrary moment you call it eg. statistically never on the second.
Worse, if your instructions take longer than a second to process, then I guess you just sleep from that moment - leading to a reality where every Ruby minute has "60, or fewer" seconds. That's some bullshit!
I was embarrassed that Ruby couldn't just reliably syncronize with the NYE ball drop or a NASA countdown.
Ruby doesn't give us a way to execute code on the second, but ChronoTrigger gets close enough to fake it, convincingly, in a non-blocking and resource-efficient way.
That makes ChronoTrigger a bit of an eccentric, as libraries go.
Design concepts and goals
Not a replacement for ActiveJob (or cron!)
Events are ephemeral and disposable; failure should be fine 🤷
Borrow the best ideas from the ActiveJob and CableReady APIs
ActiveSupport::TimeWithZone all the way down
All times are today, rounded to 1s for easy comparison
Times are memoized to avoid side effects
Events should be short term and soon; there is no tomorrow
Run in-process with no additional infrastructure dependencies
Why not ActiveJob?
ActiveJob is amazing, but creating Jobs for typical ChronoTrigger use cases feels like taking a taxi to the next house.
Jobs are not designed to run immediately, and priority should be given to important things like mail delivery. There's also functionality in the Event class that would be hard to retrofit to Job classes.
It's also worth mentioning that requiring Sidekiq would require Heroku users to set up a worker dyno, even if you're not using ActiveJob. Finally, Sidekiq sometimes runs jobs multiple times!
ChronoTrigger Time
There are some simple laws which govern how time works when using ChronoTrigger:
"Yesterday" and "tomorrow" are lies; every day is today. When
23:59:11flips over, it is now00:00:00, todayAll times are represented as
ActiveSupport::TimeWithZoneThere is no unit of time shorter than one second, and all times have their precision rounded down to the second
These requirements make it easy to both compare times and do time calculations like right_now + 1.minute or moment_in_the_future(16.seconds.from_now).
ChronoTrigger events are designed to be low-stakes and they are supposed to happen soon. Otherwise, ActiveJob or cron are likely better suited to your problem.
Ticks 🐞🐞🐞
Ticks are how ChronoTrigger refers to the beginning of the next clock second. It's always less than a second away. Don't blink! 😲
From the moment your server boots and the Clock starts, every second is a new tick. You can actually see how many ticks have passed since the server was started by running the ticks helper method inside your event's perform method, or directly inspecting the Clock itself:
You might find creative uses for ticks, especially if you sometimes pause the Clock.
In such a scenario, you might find yourself wondering how many ticks have occurred, even if far more IRL time has passed.
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