Problematic spec repro

test2.rb

$stdout.sync = true
$stderr.sync = true

require "socket"
require "timeout"

module PortProber
  module_function

  def random(host)
    server = TCPServer.new(host, 0)
    port   = server.addr[1]

    port
  ensure
    server&.close
  end

  # rubocop:disable Lint/RescueWithoutErrorClass
  def port_open?(ip, port)
    Timeout.timeout(0.1) do                     # <--- Low timeout gets you dangling puma cluster worker
      TCPSocket.new(ip, port).close
      true
    end
  rescue
    false
  end
  # rubocop:enable all

  def localhost
    info = Socket.getaddrinfo("localhost",
                              80,
                              Socket::AF_INET,
                              Socket::SOCK_STREAM)

    raise "unable to translate 'localhost' for TCP + IPv4" if info.empty?

    info[0][3]
  end
end

# puts $PID
# puts %x`ps -p #{$PID}`

ip   = PortProber.localhost
port = PortProber.random(ip)

puts "#{ip}:#{port}"

env = { "PORT" => port.to_s }
command = "bundle exec puma -C config/puma.rb"
r_out, w_out = IO.pipe
pid = Process.spawn(env, command, out: w_out, err: "/dev/null")
Process.detach(pid)

def running?(pid)
  Process.getpgid(pid)
  true
rescue Errno::ESRCH # No such process
  false
end

def not_running_or_port_open?(pid, ip, port)
  not_running = !running?(pid)
  port_open   = PortProber.port_open?(ip, port)

  not_running || port_open
end

sleep 0.01 until not_running_or_port_open?(pid, ip, port)

# puts pid
# puts %x`ps -p #{pid}`

begin
  Process.kill(:INT, pid)
  Process.wait(pid)
rescue Errno::ESRCH, Errno::ECHILD
end

[r_out, w_out].each(&:close)

puts
puts %x`ps aux | grep puma ; ps aux | grep ruby`

$ ruby test2.rb
127.0.0.1:49743

dentarg          66846   1.5  0.1  2552568  26564 s006  R+    5:40PM   0:00.03 puma: cluster worker 0: 66840 [seikan]
dentarg          66851   0.0  0.0  2432804   1964 s006  S+    5:40PM   0:00.00 grep puma
dentarg          66849   0.0  0.0  2442612   2316 s006  S+    5:40PM   0:00.00 sh -c ps aux | grep puma ; ps aux | grep ruby
dentarg          66839   1.5  0.0  2468656   9692 s006  S+    5:40PM   0:00.09 ruby test2.rb
dentarg          66849   1.0  0.0  2442612   2316 s006  S+    5:40PM   0:00.00 sh -c ps aux | grep puma ; ps aux | grep ruby
dentarg          66853   0.0  0.0  2432804   1972 s006  S+    5:40PM   0:00.00 grep ruby