Am I able to implement a background event loop that runs forever using this library

[stan-stately]

im trying to write an auth token provider. This provider needs to fetch tokens in the background asynchronously. A minimal repro of what im trying to do is this:

# setup a global scheduler for the process
scheduler = Async::Scheduler.new
Fiber.set_scheduler(scheduler)       

class Test
  def initialize
    @res = 0
    Async do
      increment_slowly
      puts "background done: #{@res}"
    end
  end

  def get_sync
    Sync do
      increment_slowly.wait
    end
  end

  def increment_slowly
    Async do
      puts "incrementing"
      sleep(1)
      @res += 1
      @res
    end
  end

  attr_reader :res
end

I would expect the following test to pass but @res is always 0:

RSpec.describe "test" do
  it "works" do
    test = Test.new
    sleep(2)
    # background operation should have finished by now
    expect(test.res).to eql(1)
    expect(test.get_sync).to eql(2)
  end
end

Someone asked a similar question here: #268 but their solution seems over complicated.

What do you think?

[stan-stately]

I should note that I don't want to expose the fact that this provider uses async internally to consumers of my library

[ioquatix]

You should look at async-actor then: https://github.com/socketry/async-actor

You can hide whatever you want inside an event driven actor with a synchronous interface.

[stan-stately]

thanks. that worked really well

[ioquatix]

Is your library open source?

[stan-stately]

it is actually: https://github.com/StatelyCloud/ruby-sdk/blob/main/lib/common/auth/auth0_token_provider.rb

[ioquatix]

A few thoughts - of no particular significance.

You might like to make #close a little more robust, e.g.

def close
  if actor = @actor
    @actor = nil
    actor.close
  end
end

You might like to rename @actor.init to @actor.start or something that indicates that it's starting the background refresh operation.

I don't think your implementation of refresh_token returns a string, but instead returns a Task. In fact, I'd recommend adding return nil at the end of that method.

class Actor seems like it could be named something more specific to the task at hand, e.g. BackgroundTokenRefresher or something. The fact that you wrap it in an actor shouldn't really impact the implementation (you should in theory be able to directly invoke this code from within the event loop).

Instead of having refresh_token_impl call refresh_token recursively, I wonder if you can just do it in a loop?