Ruby headless watir-webdriver Xvfb zombies

Question

I have two apps running on a single server that perform headless browsing tasks. Each time one browses, the Xvfb process is not dying and instead becomes a zombie. I can confirm this with the following script.

require 'headless'
require 'watir-webdriver'
require 'yaml'

zombies_at_start = `ps axo pid=,stat= | awk '$2~/^Z/ { print $1 }'`.split("\n").count

5.times do
  begin
    d = YAML.load_file("/path/to/config/headless.yml")['build_number'] #=> "98"
    h = Headless.new(:display => d) 
    h.start
    b = Watir::Browser.new :firefox
    b.goto 'http://google.com'
    sleep(0.5)
  ensure
    b.close
    h.destroy
  end
  sleep(0.5)
end

zombies_at_end = `ps axo pid=,stat= | awk '$2~/^Z/ { print $1 }'`.split("\n").count

puts "Created #{zombies_at_end - zombies_at_start} more zombies." 
#=> Created 5 more zombies.

Why? How can I fix this?

---

Version info:

• xorg-x11-server-Xvfb-1.15.0-26.el6.centos.i686
• CentOS release 6.5 (Final)
• ruby-2.0.0-p353
• rvm 1.25.25
• selenium-webdriver (2.45.0, 2.44.0)
• watir-webdriver (0.7.0)
• headless (2.1.0)

Answer 1

UPDATE: A pull request submitted to Headless to wait by default was accepted. Woo!

---

The gem headless changed the way it starts, stops (kills) and verifies the Xvfb process. Though I'm not entirely sure why, but on CentOS 6 this causes the process to zombify. Since the .destroy wasn't causing issues previously, it must be related to the way headless starts the Xvfb process (which was re-written simultaneously).

However, the gem simultaneously introduced .destroy_sync, which waits for the process to die, and does not create zombies.

require 'headless'
require 'watir-webdriver'
require 'yaml'

zombies_at_start = `ps axo pid=,stat= | awk '$2~/^Z/ { print $1 }'`.split("\n").count

5.times do
  begin
    d = YAML.load_file("/path/to/config/headless.yml")['build_number'] #=> "98"
    h = Headless.new(:display => d) 
    h.start
    b = Watir::Browser.new :firefox
    b.goto 'http://google.com'
    sleep(0.5)
  ensure
    b.close
    # h.destroy
    h.destroy_sync
  end
  sleep(0.5)
end

zombies_at_end = `ps axo pid=,stat= | awk '$2~/^Z/ { print $1 }'`.split("\n").count

puts "Created #{zombies_at_end - zombies_at_start} more zombies." 
#=> Created 0 more zombies.