Chef is awesome, but it’s also very easy to go overboard. In terms of testing and maintainability, sometimes its better to refactor your long recipe into an LWRP. As your infrastructure evolves, so should you cookbooks. But at some point your bound to have a cookbook 500+ lines of antiquated logic. How do you refactor such a large chunk of code that is critical to your infrastructure? How much logic should me moved into other cookbooks? How much logic should be extracted into LWRPs? How much logic should be moved out of Chef, into Ruby, and packaged as a gem?

1. Cookbook
Refactoring
A

2. Cookbook
Refactoring
... and extracting logic into Rubygems
A

3. sethvargo@opscode.com
E
byz

5. We're Hiring!

6. We're Hiring!
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THIS

11. template '/etc/hosts' do
owner 'root'
group 'root'
source 'etc/hosts'
end
recipes/default.rb

12. # This file is managed by Chef for "<%= node['fqdn'] %>"
# Do NOT modify this file by hand.
<%= node['ipaddress'] %> <%= node['fqdn'] %>
127.0.0.1!localhost <%= node['fqdn'] %>
255.255.255.255!broadcasthost
::1 localhost
fe80::1%lo0! localhost
templates/default/etc/hosts.erb

14. default['etc']['hosts'] = [] unless node['etc']['hosts']
attributes/default.rb

15. # This file is managed by Chef for "<%= node['fqdn'] %>"
# Do NOT modify this file by hand.
<%= node['ipaddress'] %> <%= node['fqdn'] %>
127.0.0.1!localhost <%= node['fqdn'] %>
255.255.255.255!broadcasthost
::1 localhost
fe80::1%lo0! localhost
# Custom Entries
<% node['etc']['hosts'].each do |h| -%>
<%= h['ip'] %> <%= h['host'] %>
<% end -%>
templates/default/etc/hosts.erb

16. include_attribute 'hostsfile'
default['etc']['hosts'] << {
'ip' => '1.2.3.4',
'host' => 'www.example.com'
}
other_cookbook/attributes/default.rb

17. node.default['etc']['hosts'] << {
'ip' => '1.2.3.4',
'host' => 'www.example.com'
}
other_cookbook/recipes/default.rb

18. default_attributes({
'etc' => {
'hosts' => [
{'ip' => '1.2.3.4', 'host' => 'www.example.com'},
{'ip' => '4.5.6.7', 'host' => 'foo.example.com'}
]
}
})
roles/my_role.rb

19. {
"default_attributes": {
"etc": {
"hosts": [
{"ip": "1.2.3.4", "host": "www.example.com"},
{"ip": "4.5.6.7", "host": "foo.example.com"}
]
}
}
}
environments/production.json

21. node.set['etc']['hosts'] = {
ip: '7.8.9.0',
host: 'bar.example.com'
})
recipes/default.rb

23. arr = [1,2,3]
arr << 4 => [1,2,3,4]
arr = 4 => 4

24. arr = [1,2,3]
arr << 4 => [1,2,3,4]
arr = 4 => 4
Not an Array

25. TODO:Add infographics
# This file is managed by Chef for "www.myapp.com"
# Do NOT modify this file by hand.
1.2.3.4 www.myapp.com
127.0.0.1!localhost www.myapp.com
255.255.255.255!broadcasthost
::1 localhost
fe80::1%lo0! localhost
# Custom Entries
1.2.3.4 www.example.com
4.5.6.7 foo.example.com
7.8.9.0 bar.example.com
/etc/hosts

26. TODO:Add infographics
# This file is managed by Chef for "www.myapp.com"
# Do NOT modify this file by hand.
1.2.3.4 www.myapp.com
127.0.0.1!localhost www.myapp.com
255.255.255.255!broadcasthost
::1 localhost
fe80::1%lo0! localhost
# Custom Entries
7.8.9.0 bar.example.com
/etc/hosts

27. Post Mortem

30. << =

31. << =!=

32. Post Mortem
Action Items
7

33. Monkey patch Chef to raise an
exception when redefining that
particular node attribute.

34. Monkey patch Chef to raise an
exception when redefining that
particular node attribute.t

35. Create a special cookbook that
uses a threshold value and raises an
exception if the size of the array
doesn't "make sense".

36. Create a special cookbook that
uses a threshold value and raises an
exception if the size of the array
doesn't "make sense".
t

37. Move all entries to a data bag

38. Move all entries to a data bag
u

39. Move all entries to a data bag6
6 Add tests

40. Data Bags

41. [
"1.2.3.4 example.com www.example.com",
"4.5.6.7 foo.example.com",
"7.8.9.0 bar.example.com"
]
data_bags/etc_hosts.json

42. hosts = data_bag('etc_hosts')
template '/etc/hosts' do
owner 'root'
group 'root'
source 'etc/hosts'
variables(
hosts: hosts
)
end
recipes/default.rb

43. # This file is managed by Chef for "<%= node['fqdn'] %>"
# Do NOT modify this file by hand.
<%= node['ipaddress'] %> <%= node['fqdn'] %>
127.0.0.1!localhost <%= node['fqdn'] %>
255.255.255.255!broadcasthost
::1 localhost
fe80::1%lo0! localhost
# Custom Entries
<%= @hosts.join("n") %>
templates/default/etc/hosts.erb

44. Move all entries to a data bag5
6 Add tests

45. require 'chefspec'
spec/default_spec.rb

46. require 'chefspec'
describe 'hostsfile::default' do
end
spec/default_spec.rb

47. require 'chefspec'
describe 'hostsfile::default' do
let(:hosts) { ['1.2.3.4 example.com', '4.5.6.7 bar.com'] }
before do
Chef::Recipe.any_instance.stub(:data_bag).with('etc_hosts').and_return(hosts)
end
end
spec/default_spec.rb

48. require 'chefspec'
describe 'hostsfile::default' do
let(:hosts) { ['1.2.3.4 example.com', '4.5.6.7 bar.com'] }
before do
Chef::Recipe.any_instance.stub(:data_bag).with('etc_hosts').and_return(hosts)
end
let(:runner) { ChefSpec::ChefRunner.new.converge('hostsfile::default') }
end
spec/default_spec.rb

49. require 'chefspec'
describe 'hostsfile::default' do
let(:hosts) { ['1.2.3.4 example.com', '4.5.6.7 bar.com'] }
before do
Chef::Recipe.any_instance.stub(:data_bag).with('etc_hosts').and_return(hosts)
end
let(:runner) { ChefSpec::ChefRunner.new.converge('hostsfile::default') }
it 'loads the data bag' do
Chef::Recipe.any_instance.should_receive(:data_bag).with('etc_hosts')
end
end
spec/default_spec.rb

50. require 'chefspec'
describe 'hostsfile::default' do
let(:hosts) { ['1.2.3.4 example.com', '4.5.6.7 bar.com'] }
before do
Chef::Recipe.any_instance.stub(:data_bag).with('etc_hosts').and_return(hosts)
end
let(:runner) { ChefSpec::ChefRunner.new.converge('hostsfile::default') }
it 'loads the data bag' do
Chef::Recipe.any_instance.should_receive(:data_bag).with('etc_hosts')
end
it 'creates the /etc/hosts template' do
expect(runner).to create_template('/etc/hosts').with_content(hosts.join("n"))
end
end
spec/default_spec.rb

51. $ rspec cookbooks/hostsfile
Running all specs

52. $ rspec cookbooks/hostsfile
Running all specs
**
Finished in 0.0003 seconds
2 examples, 0 failures

53. $ rspec cookbooks/hostsfile
Running all specs
**
Finished in 0.0003 seconds
2 examples, 0 failures
Really Fucking Fast™

54. #winning

55. 10,000 tests

56. 28 seconds

57. #winning

58. ⏳⏳

61. hosts = data_bag('etc_hosts')
hosts << search(:node, 'role:mongo_master').first.tap do |n|
"#{n['ip_address']} #{n['fqdn']}"
end
template '/etc/hosts' do
owner 'root'
group 'root'
source 'etc/hosts'
variables(
hosts: hosts
)
end
recipes/default.rb

62. hosts = data_bag('etc_hosts')
hosts << search(:node, 'role:mongo_master').first.tap do |n|
"#{n['ip_address']} #{n['fqdn']}"
end
hosts << search(:node, 'role:mysql_master').first.tap do |n|
"#{n['ip_address']} #{n['fqdn']}"
end
hosts << search(:node, 'role:redis_master').first.tap do |n|
"#{n['ip_address']} #{n['fqdn']}"
end
template '/etc/hosts' do
owner 'root'
group 'root'
recipes/default.rb

63. LWRPs

64. # List of all actions supported by the provider
actions :create, :create_if_missing, :update, :remove
# Make create the default action
default_action :create
# Required attributes
attribute :ip_address,
kind_of: String,
name_attribute: true,
required: true
attribute :hostname, kind_of: String
# Optional attributes
attribute :aliases, kind_of: Array
attribute :comment, kind_of: String
resources/entry.rb

65. action :create do
::Chef::Util::FileEdit.search_file_delete_line(entry)
::Chef::Util::FileEdit.insert_line_after_match(/n/, entry)
end
protected
def entry
[new_resource.ip_address, new_resource.hostname,
new_resource.aliases.join(' ')].compact.join(' ').squeeze(' ')
end
providers/entry.rb

66. hostsfile_entry '1.2.3.4' do
hostname 'example.com'
end
providers/entry.rb

67. Chef::Util::FileEdit is slow

68. Re-writing the file on each run

69. Provider kept growning

70. Untested

71. Refactor
A

72. Move to pure Ruby classes

73. Ditch Chef::Util::FileEdit and
manage the entire file

74. Only implement Ruby classes in
the Provider (logic-less Provider)

75. Test the Ruby code

76. Test that the Provider implements
the proper Ruby classes

77. TODO:Add infographics
class Entry
attr_accessor :ip_address, :hostname, :aliases, :comment
def initialize(options = {})
if options[:ip_address].nil? || options[:hostname].nil?
raise ':ip_address and :hostname are both required options'
end
@ip_address = options[:ip_address]
@hostname = options[:hostname]
@aliases = [options[:aliases]].flatten
@comment = options[:comment]
end
# ...
end
libraries/entry.rb

78. TODO:Add infographics
class Manipulator
def initialize
contents = ::File.readlines(hostsfile_path)
@entries = contents.collect do |line|
Entry.parse(line) unless line.strip.nil? || line.strip.empty?
end.compact
end
def add(options = {})
@entries << Entry.new(
ip_address: options[:ip_address],
hostname: options[:hostname],
aliases: options[:aliases],
comment: options[:comment]
)
end
end
libraries/manipulator.rb

79. # Creates a new hosts file entry. If an entry already exists, it
# will be overwritten by this one.
action :create do
hostsfile.add(
ip_address: new_resource.ip_address,
hostname: new_resource.hostname,
aliases: new_resource.aliases,
comment: new_resource.comment
)
new_resource.updated_by_last_action(true) if hostsfile.save
end
providers/entry.rb

82. RSpec

83. TODO:Add infographics
describe Entry do
describe '.initialize' do
subject { Entry.new(ip_address: '2.3.4.5', hostname:
'www.example.com', aliases: ['foo', 'bar'], comment: 'This is a
comment!', priority: 100) }
it 'raises an exception if :ip_address is missing' do
expect {
Entry.new(hostname: 'www.example.com')
}.to raise_error(ArgumentError)
end
it 'sets the ip_address' do
expect(subject.ip_address).to eq('2.3.4.5')
end
end
spec/entry_spec.rb

85. ChefSpec

86. ChefSpec

87. TODO:Add infographics
describe 'hostsfile lwrp' do
let(:manipulator) { double('manipulator') }
before do
Manipulator.stub(:new).and_return(manipulator)
Manipulator.should_receive(:new).with(kind_of(Chef::Node))
.and_return(manipulator)
manipulator.should_receive(:save!)
end
let(:chef_run) {
ChefSpec::ChefRunner.new(
cookbook_path: $cookbook_paths,
step_into: ['hostsfile_entry']
)
}
spec/default_spec.rb

88. TODO:Add infographics
context 'actions' do
describe ':create' do
it 'adds the entry' do
manipulator.should_receive(:add).with({
ip_address: '2.3.4.5',
hostname: 'www.example.com',
aliases: nil,
comment: nil,
priority: nil
})
chef_run.converge('fake::create')
end
end
end
end

89. Open It

95. Gem It

96. $ bundle gem hostsfile

97. $ bundle gem hostsfile
create hostsfile/Gemfile
create hostsfile/Rakefile
create hostsfile/LICENSE.txt
create hostsfile/README.md
create hostsfile/.gitignore
create hostsfile/hostsfile.gemspec
create hostsfile/lib/hostsfile.rb
create hostsfile/lib/hostsfile/version.rb
Initializating git repo in ~Development/hostsfile

98. entry.rb
manipulator.rb
99

99. 9

100. 9
?

101. chef_gem 'hostsfile'
recipes/default.rb

102. require 'hostsfile'
providers/entry.rb

103. In another cookbook...

104. # ...
depends 'hostsfile'
other_cookbook/metadata.rb

105. {
"run_list": [
"recipe[hostsfile]"
]
}
www.myapp.com (Chef Node)

109. Thank
You
z