Timer

A versatile timer module utilizing Crystal scheduler.

About

Timer class makes it easy to execute code at some later moment of time. It is fast, performant and reliable.

Installation

1. Add the dependency to your shard.yml:

dependencies:
  timer:
    github: vladfaust/timer.cr
    version: ~> 0.1.0

2. Run shards install

This shard follows Semantic Versioning v2.0.0, so check releases and change the version accordingly. Note that until Crystal is official released, this shard would be in beta state (0.*.*), with every minor release is breaking. For example, 0.1.0 → 0.2.0 is considered breaking and 0.1.0 → 0.1.1 is not.

Usage

Basic example:

require "timer"

Timer.new(1.second) do
  puts "Triggered"
end

sleep # Will print "Triggered" after 1 second

Example with select:

channel = Channel(Nil).new

select
when channel.receive
  puts "Never happens"
when Timer.new(1.second)
  puts "Timeout!"
end

sleep # Will print "Timeout!" after 1 second

You can #postpone and #reschedule a timer, but note that the latter has bigger performance impact and should only be used when rescheduling to an earlier time.

at = Time.utc_now + 5.minutes

timer = Timer.new(at) do
  puts "Triggered"
end

# OK, will trigger in 6 minutes from now
timer.postpone(1.minute)

# Worse performance than `#postpone`, but still works
timer.reschedule(Time.utc_now + 6.minutes)

# OK, will trigger in 1 minute from now (i.e. eariler)
timer.reschedule(Time.utc_now + 1.minute)

Note that a timer can be scheduled at a moment in the past, which means that it would be triggered immediately after given control by the Crystal scheduler.

You can also #trigger the timer immediately (still calling the block in another fiber), or #cancel it completely.

Development

crystal spec and you're good to go.

Contributing

1. Fork it (https://github.com/vladfaust/timer.cr/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'feat: some feature') using Conventional Commits specs
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Vlad Faust - creator and maintainer