Fork safe connection pool in Ruby. Not elegant.

fork_safe.rb

require 'connection_pool'

def open_pool
  pool = ConnectionPool.new { File.open('/dev/null', 'r') }
  class << pool
    def fileno
      with { |fd| fd.fileno }
    end
  end
  pool
end

$global_pool = open_pool

module RenewConnectionFork
  def fork(&b)
    v = super() do
      $global_pool = open_pool
      b.call
    end
  end
end

class Object
  prepend RenewConnectionFork
end

puts "#{Process.pid}global: #{$global_pool.fileno}"

fork do
  puts "#{Process.pid}  global: #{$global_pool.fileno}"
end

sleep 1

puts "#{Process.pid}global: #{$global_pool.fileno}"

#--output
# 43873global: 7
# 43886  global: 10
# 43873global: 7