Asynr

(This gem is a rebuild of a previous one located at the same Github repository). \ Asynr is a gem to perform asynchronous tasks by evaluating directly classes and entrypoints. This is highly inspired by Rufus-Scheduler.

How it works ?

When you want to create a scheduler running several tasks separated by classes, you can instantiate Asynr and launch them asynchronously an easy way. \ Asynr is based-upon Ruby threads and requires no dependency.

# example
require "asynr"
Dir.glob(Dir.pwd + "/lib/*_class.rb").each &method(:require)

class Worker
  def self._start
    scheduler = Asynr.new
    scheduler.in 3, ARandomClass
    scheduler.every 3600, 2, AnotherClass, {entrypoint: :new}
    scheduler.at (Time.now + 10), AgainAnother, {arg1: :hello, arg2: :world}

    scheduler.start
  end
end

• We require asynr and all the files containing independant classes.
• We instantiate a new scheduler, which is gonna be empty
• We create .in, .every and .at jobs (read definitions)
• We start it

launch a job in two days

secrets = File.read '/a/secret/path/secrets.txt'

scheduler = Asynr.new
scheduler.at (Time.now + (3600 * 24) * 2), BackupFiles, {password: secrets}
scheduler.start

In this example, we are using the arguments API of Asynr. It allows us to bind any value to any key when calling a .in, .every or .at method.

launch a job every hour

url = "https://acoolwebsitetoscrap.com"

scheduler = Asynr.new
scheduler.every 3600, 0, WebScrapper, {entrypoint: :new, url: url, save_to: "/tmp/scrapper"}
scheduler.start

We typically want to download a whole page every hour since it may change soon. This snippet allows you to send the url and the path where you want to save scrapped file. \

Entrypoint argument

Entrypoint is a quite special argument, since it allows you to select which class method is gonna be called by the class evaluator. new allows you to create objects, and the default value is self._entrypoint.

Here is what a default Asynr-compliante class may look like.

class WebScrapper
  def self._entrypoint(*args)
    body = AnyHTTPLib.get(URI.parse(args[:url])).body
    f = File.open("%s/%s" % [args[:save_to], Time.now.strftime('%y-%m-%d')])
    f.puts body
    f.close
  end
end

Launch a job in two minutes

scheduler = Asynr.new
scheduler.in 120, PrintHelloWorld

This is a quite easy method to understand. Please mind you are free to put arguments at the end of this line or select another entrypoint than _entrypoint.

Why an entrypoint ?

Ruby doesn't have any entrypoint function as main() could be one in Go, for example. This function is typically intended to provide a "entrypoint" where function-calls tree will be created and attached to. Since Ruby doesn't have it, without a entrypoint method, Asynr wouldn't be able to load and execute the class in a cool way. \ I called this temporary main method _entrypoint. The _ means it is special and it allows us to avoid common names mistakes. This method must be registred as self into a class to be called as it.

class RandomTest ; def self._entrypoint(*args) ; end ; end

You can override this parameter (in order to create instance through .new method, for example) by adding a {entrypoint: :any_method} argument to .in, .every and .at methods. \ Please note the *args method parameter. It allows us to bind any information comming from the scheduler to attach it into the entrypoint method. \ Working example :

url = "https://rubygems.org"

scheduler = Asynr.new
scheduler.in 3, DisplaySomething, {text: url}

class DisplaySomething
  def self._entrypoint(*args)
    puts args[:text]
  end
end