The thread objects stay the "same" as the parent memory is copied down to the forked child, so watch out for bad TLVs values.

See:

• https://bugs.ruby-lang.org/issues/17795
• https://github.com/rails/rails/blob/main/activesupport/lib/active_support/fork_tracker.rb
• https://github.com/typhoeus/typhoeus/blob/a345545e5e4ac0522b883fe0cf19e5e2e807b4b0/lib/typhoeus/pool.rb#L34-L42
• https://github.com/Shopify/rails/blob/411ccbdab2608c62aabdb320d52cb02d446bb39c/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L946
• http://sequel.jeremyevans.net/rdoc/files/doc/fork_safety_rdoc.html

Puma

before_fork do
  Sequel::DATABASES.each(&:disconnect)
end

Parallel

If you’re using the Parallel gem with processes, you should disconnect before calling it:

Sequel::DATABASES.each(&:disconnect)
Parallel.map(['a','b','c'], in_processes: 3) { |one_letter| }