tasker
Tasker
A high precision scheduler for crystal lang. Allows you to schedule tasks to run in the future and obtain the results.
Usage
At a time in the future
Tasker.at(20.seconds.from_now) { perform_action }
# If you would like the value of that result
# returns value or raises error - a Future
Tasker.at(20.seconds.from_now) { perform_action }.get
After some period of time
Tasker.in(20.seconds) { perform_action }
Repeating every time period
task = Tasker.every(2.milliseconds) { perform_action }
# Canceling stops the schedule from running
task.cancel
# Resume can be used to restart a canceled schedule
task.resume
You can grab the values of repeating schedules too
tick = 0
task = Tasker.every(2.milliseconds) { tick += 1; tick }
# Calling get will pause until after the next schedule has run
task.get == 1 # => true
task.get == 2 # => true
task.get == 3 # => true
# It also works as an enumerable
# NOTE:: this will only stop counting once the schedule is canceled
task.each do |count|
puts "The count is #{count}"
task.cancel if count > 5
end
Running a CRON job
# Run a job at 7:30am every day
Tasker.cron("30 7 * * *") { perform_action }
# For running in a job in a particular time zone:
berlin = Time::Location.load("Europe/Berlin")
Tasker.cron("30 7 * * *", berlin) { perform_action }
# Also supports pause, resume and enumeration
Timeout an operation NOTE:: technically the operation isn't cancelled on timeout as there is no fiber cancel in crystal yet / no way to unwind stack consistently
# Run some code that is expected to complete within a certain time period
result = Tasker.timeout(10.seconds) { perform_action }
Pipelines
a non-blocking, asynchronous pipeline where each step only processes the input if it's not already processing the previous input.
pipeline = Tasker::Pipeline(Input, Output).new("name") do |input|
process(input) # => Output
end
pipeline.chain { |output_of_first_step|
next_step(output_of_first_step)
}.subscribe { |output|
# a subscribe step is always run, even if it's already running
publish output
}
The idea is to maximise throughput with minimal latency.
Make sure to use the -Dpreview_mt
flag when building.