scout_apm_ruby Scout causes Puma to run the on_worker

scout_apm (2.4.21) Scout is causing Puma to execute the on_worker_boot twice, only when preloading is turned on on puma. This file (https://github.com/scoutapp/scout_apm_ruby/blob/master/lib/scout_apm/server_integrations/puma.rb) gave me the hint by logging I, [2019-03-07T16:47:33.844521 #186] INFO -- : Installing Puma worker loop. when I tought it was a Puma configuration issue. Production or Development env is the same. If i remove the gem and bundle it stops running twice.

preload off

[225] Puma starting in cluster mode... [225] * Version 3.12.0 (ruby 2.5.1-p57), codename: Llamas in Pajamas [225] * Min threads: 0, max threads: 1 [225] * Environment: development [225] * Process workers: 1 [225] * Phased restart available [225] * Listening on tcp://0.0.0.0:3000 [225] Use Ctrl-C to stop --before_fork-start --before_fork-end worker 0=>--on_worker_fork-- worker 0=>--after_worker_fork-- worker 0=>--on_worker_boot-- [225] - Worker 0 (pid: 228) booted, phase: 0 ... [225] - Gracefully shutting down workers... worker 0=>--on_worker_shutdown-- [225] === puma shutdown: 2019-03-07 16:57:53 +0000 === [225] - Goodbye!

preload on

[275] Puma starting in cluster mode... [275] * Version 3.12.0 (ruby 2.5.1-p57), codename: Llamas in Pajamas [275] * Min threads: 0, max threads: 1 [275] * Environment: development [275] * Process workers: 1 [275] * Preloading application [275] * Listening on tcp://0.0.0.0:3000 [275] Use Ctrl-C to stop --before_fork-start --before_fork-end worker 0=>--on_worker_fork-- worker 0=>--after_worker_fork-- worker 0=>--on_worker_boot-- I, [2019-03-07T17:01:58.601184 #278] INFO -- : Installing Puma worker loop. worker 0=>--on_worker_boot-- [275] - Worker 0 (pid: 278) booted, phase: 0 ... [275] - Gracefully shutting down workers... worker 0=>--on_worker_shutdown-- [275] === puma shutdown: 2019-03-07 17:02:03 +0000 === [275] - Goodbye!