Asynchronous, non-blocking background execution in Ruby script

Question

I am trying to execute some code in a non-blocking way.

In my real scenario, this would be an expensive SQL query in a Ruby on Rails app, however, as a test for replicating the scenario, I made this Ruby script:

#!/usr/bin/env ruby

require 'async'

puts 'hello'

Async do
  sleep 2
  puts 'hi'
end

puts 'there'

My expectation would be to see:

hello
there

immediately. However, what I actually get, is:

hello
hi
there

after two seconds.

I don't care about the return value of the async call — I just want to execute some code in the background and exit immediately.

Is there a way to do this in Ruby 3?

"execute some code in the background and exit immediately" – if you exit (as in terminate the Ruby script / process), your code won't run anymore. For background tasks in Rails, have a look at Active Job or Sidekiq — Stefan
– Stefan, Commented Jan 13, 2023 at 18:41

Chiara Ani · Accepted Answer · 2023-01-13 17:30:25Z

2

You easily do this using a thread.

puts 'hello'

# Async == Thread
Thread.new do
  sleep 2
  puts 'hi'
end

puts 'there'
``

answered Jan 13, 2023 at 17:30

Chiara Ani

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1 Comment

Stefan Over a year ago

Note that without join the sub thread will be killed as soon as the main thread printed "there". It doesn't keep running on its own.

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