About Libraries
/libraries directory. Because a
library is built using Ruby, anything that can be done with Ruby can be
done in a library file, including advanced functionality such as
extending built-in Chef classes.Use a library to:
- Connect to a database
- Fetch secrets from a cloud provider
- Talk to an LDAP provider
- Do anything that can be done with Ruby
Syntax
The syntax for a library varies because library files are created using Ruby and are designed to handle custom situations. See the Examples section below for samples.
Template Helper Modules
A template helper module can be defined in a library. This is useful when extensions need to be reused across recipes or to make it easier to manage code that would otherwise be defined inline for each recipe basis.
template '/path/to/template.erb' do
helpers(MyHelperModule)
end
Examples
The following examples show how to use cookbook libraries.
Create a Namespace
A database can contain a list of virtual hosts that are used by customers. A custom namespace could be created that looks something like:
# Sample provided by "Arjuna (fujin)". Thank you!
require 'sequel'
class Chef::Recipe::ISP
# We can call this with ISP.vhosts
def self.vhosts
v = []
@db = Sequel.mysql(
'web',
user: 'example',
password: 'example_pw',
host: 'dbserver.example.com'
)
@db[
"SELECT virtualhost.domainname,
usertable.userid,
usertable.uid,
usertable.gid,
usertable.homedir
FROM usertable, virtualhost
WHERE usertable.userid = virtualhost.user_name"
].all do |query|
vhost_data = {
servername: query[:domainname],
documentroot: query[:homedir],
uid: query[:uid],
gid: query[:gid],
}
v.push(vhost_data)
end
Chef::Log.debug('About to provision #{v.length} vhosts')
v
end
end
After the custom namespace is created, it could then be used in a recipe, like this:
ISP.vhosts.each do |vhost|
directory vhost[:documentroot] do
owner vhost[:uid]
group vhost[:gid]
mode '0755'
action :create
end
directory "#{vhost[:documentroot]}/#{vhost[:domainname]}" do
owner vhost[:uid]
group vhost[:gid]
mode '0755'
action :create
end
end
Extend a Recipe
A customer record is stored in an attribute file that looks like this:
mycompany_customers({
bob: {
homedir: '/home/bob',
webdir: '/home/bob/web',
},
}
)
A simple recipe may contain something like this:
directory node["mycompany_customers"]["bob"]["webdir"] do
owner 'bob'
group 'bob'
action :create
end
Or a less verbose version of the same simple recipe:
directory customer(:bob)[:webdir] do
owner 'bob'
group 'bob'
action :create
end
A simple library could be created that extends Chef::Recipe::, like
this:
class Chef
class Recipe
# A shortcut to a customer
def customer(name)
node["mycompany_customers"][name]
end
end
end
Loop Over a Record
A customer record is stored in an attribute file that looks like this:
mycompany_customers({
bob: {
homedir: '/home/bob',
webdir: '/home/bob/web',
},
}
)
If there are many customer records in an environment, a simple recipe can be used to loop over every customer, like this:
all_customers do |name, info|
directory info[:webdir] do
owner name
group name
action :create
end
end
A simple library could be created that extends Chef::Recipe::, like
this:
class Chef
class Recipe
def all_customers(&block)
node["mycompany_customers"].each do |name, info|
block.call(name, info)
end
end
end
end