Data Driven Cookbooks

Code vs Data

Code vs Data

  • once the data is taken out of the code then cookbook become generic.
  • Generic cookbook can be used with any OS and environments.
  • Reusability helps in reducing tonnes and tonnes of time.

Node Object

  • It is the representation of each node on chef server in JSON format.
  • If we run a chef-client it generates a node object in chef server in case of nodes or in workstation (/nodes/*.json) in case of running locally in workstation.

Attributes

It is used to specify a detail about node. - Attributes are used by the chef-client to understand; - The current state of the node - What the state of the node was at the end of the previous chef-client run - What the state of the node should be at the end of the current chef-client run - Attributes are taken in precedence, according to the place where we specify them, as follows;

System Defined Attributes

OHAI

  • It installs along with chef-client.
  • It helps in getting all the information about nodes
  • Finding information on node with ohai
ohai
ohai ipaddress
ohai hostname
ohai memory
ohai memory/total
ohai cpu/model_name
  • Referring attributes
node['ipaddress']
node['hostname']
node['memory']['total']
node['cpu']['model_name']

User Defined Attributes

  • User defined attributes are located in four places as follows
  • Attributes file
  • Recipes
  • Roles
  • Environments

Attribute File

  • How the attribute file looks like?

Attributes file

  • Precedence is defined

  • Attribute and its value is defined as per the above format.

  • Now we can access these attributes in recipe or template as shown below.

Accessing Attributes

Example

template node['tomcat']['config'] do
  source 'tomcat.conf.erb'
  owner node['tomcat']['user']
  group node['tomcat']['group']
  mode '0644'
  action :create
  notifies :restart, "service[#{node['tomcat']['service']}]", :delayed
end

Parameterizing Tomcat Configurations

  • Now let us start creating attribute file
  • Use chef generate to create a file in tomcat cookbook
chef generate attribute cookbooks/tomcat default
  • It will create a file as follows cookbooks/tomcat/attributes/default.rb
  • Now we add the attributes and its value in default.rb
  • Path: cookbooks/tomcat/attributes/default.rb
default['tomcat']['user'] = 'tomcat'
default['tomcat']['group'] = 'tomcat'
default['tomcat']['config'] = '/etc/tomcat/tomcat.conf'
default['tomcat']['packages'] = [ 'tomcat', 'tomcat-webapps' ]
default['tomcat']['service'] = 'tomcat'
  • Now call these attributes in the following recipes
  • tomcat::config will be changed as follows
cookbook_file node['tomcat']['config'] do
  source 'tomcat.conf'
  owner node['tomcat']['user']
  group node['tomcat']['group']
  mode '0644'
  action :create
  notifies :restart, "service[#{node['tomcat']['service']}]", :delayed
end
  • tomcat::install will be changed as follows
package node['tomcat']['packages']
  • tomcat::service will be changed as follows
service node['tomcat']['service'] do
   action [ :start, :enable]
end
  • Now apply it using kitchen converge and then verify using kitchen verify.

Platform Specific cookbooks

  • Let us convert our first created base.rb recipe into a cookbook.
  • Create a cookbook using chef generate
chef generate cookbook cookbooks/base
  • Now move the base.rb to default.rb of base cookbook.
mv /workspace/chapter3/base.rb cookbooks/base/recipes/default.rb
  • Add base::default recipe to the run_list
knife node run_list add app1 "recipe[base]"
  • Apply on node1
ssh devops@node1
sudo chef-client
  • It fails because the service name for rhel/centos is ntpd and not ntp as like debian.

centos vs ubuntu

  • To overcome this we use attribute for platform specific.
  • We use system defined attribute platform_family to do this.

Example for ohai platform_family is

root@ws:/workspace/myapp# ohai platform_family
[
  "debian"
]
root@ws:/workspace/myapp# kitchen login
Last login: Thu May  4 05:50:20 2017 from 172.17.0.1
[kitchen@9af3a004e202 ~]$ ohai platform_family
[2017-05-04T05:58:19+00:00] INFO: The plugin path /etc/chef/ohai/plugins
does not exist. Skipping...
[
  "rhel"
]
[kitchen@9af3a004e202 ~]$ logout
Connection to localhost closed.
root@ws:/workspace/myapp#
  • Now let us create a create a default attribute file for base cookbook using chef generate
chef generate attribute cookbooks/base default
  • Now add the following content to attribute file
  • Path: cookbooks/base/attributes/default.rb
case node['platform_family']
when 'rhel'
  default['ntp']['service'] = 'ntpd'
else
  default['ntp']['service'] = 'ntp'
end
  • Call the attributes in cookbooks/base/recipes/default.rb recipe
service node['ntp']['service'] do
  action [ :start, :enable ]
end
  • Now apply again using kitchen
ssh devop@node1
sudo chef-client
  • It is successful now and service is started based on platform.

Nano Project - Add some tests for recipes in base cookbook for different platform.

Templates

  • A cookbook template is an Embedded Ruby (ERB) template that is used to dynamically generate static text files.
  • Templates are great way to manage configuration files for different environment.
  • ERB or ERUBIS
  • Contains text with dynamic ruby code
  • Uses tags to mark dynamic code
  • ERB Tags
  • Code wrapped in <% %> or <% -%> is a statement that is evaluated.
  • Code wrapped in <%= %> is code that is evaluated and the result is placed into the file.
  • Harcoded strings dont have to be wrapped in erb tags if they are constant, but Ruby code must be wrapped in erb tags if you want the result of that code to go into your file.

Templatize MOTD

  • Generate motd template for base cookbook.
chef generate template cookbooks/base motd
  • Add the following content to the template file motd.erb.
  • Path: cookbooks/base/templates/default/motd.erb
This server is a property of <%= node['org']['name'] %>

      SYSTEM INFO:

       HOSTNAME   : <%= node['hostname'] %>
       IP ADDRESS : <%= node['ipaddress'] %>
       MEMORY     : <%= node['memory']['total'] %>
  • Now add organization name as a user defined attribute in attribute file
  • Path: cookbooks/base/attributes/default.rb
default['org']['name'] = "XYZ Inc."
  • Complete attribute default.rb of base cookbook is as follows
case node['platform_family']
when 'rhel'
  default['ntp']['service'] = 'ntpd'
else
  default['ntp']['service'] = 'ntp'
end

default['org']['name'] = "XYZ Inc."
  • Now add template resource to the cookbooks/base/recipes/default.rb recipe file.
template '/etc/motd' do
  source 'motd.erb'
  owner 'root'
  group 'root'
  mode  0644
end
  • Apply using kitchen converge.

Attributes Precedence

  • Declaring attributes in various places takes precedence one over another.

Attributes precedence

  • Let us take an example of declaring port as follows

Attributes precedence example

  • Now let us define organization name in recipe file, before calling attribute in any resource of a recipe.
  • Path: cookbooks/base/recipes/default.rb
node.default['org']['name'] = "School of Devops"
  • Complete recipe default.rb of base cookbook is as follows
user 'deploy' do
  uid 5001
  home '/home/deploy'
  action :create
  password '$1$Ze1eJK3R$j5I0NRP5WxbZAaeXcfYW7/'
end

user 'dojo' do
  action :remove
end

package 'ntp' do
  action :install
end

package ['tree', 'unzip', 'wget'] do
  action :install
end

package 'git'

service node['ntp']['service'] do
  action [ :start, :enable ]
end

node.default['org']['name'] = "School of Devops Inc"

template '/etc/motd' do
  source 'motd.erb'
  owner 'root'
  group 'root'
  mode  0644
end
  • Now apply using kitchen converge

Templatizing Tomcat Cookbook (LAB Exercise)

  • Generate a tomcat.conf.erb template for tomcat cookbook.
chef generate template cookbooks/tomcat tomcat.conf
  • Generate a default.rb attribute for tomcat cookbook.
chef generate attribute cookbooks/tomcat default
  • Add the following content to attribute file.
  • Path: /workspace/myapp/cookbooks/tomcat/attributes/default.rb
default['tomcat']['user'] = 'tomcat'
default['tomcat']['group'] = 'tomcat'
default['tomcat']['config'] = '/etc/tomcat/tomcat.conf'
default['tomcat']['packages'] = [ 'tomcat', 'tomcat-webapps' ]
default['tomcat']['service'] = 'tomcat'
default['tomcat']['user'] = 'tomcat'
default['tomcat']['group'] = 'tomcat'
default['tomcat']['java_home'] = '/usr/lib/jvm/jre'
default['tomcat']['catalina_home'] = '/usr/share/tomcat'
default['tomcat']['java_opts'] = '-Xms32m -Xmx64m -XX:MaxPermSize=64M  \
-Djava.security.egd=file:/dev/./urandom'
  • Add the below content to tomcat.conf.erb template.
  • Path: /workspace/myapp/cookbooks/tomcat/templates
TOMCAT_CFG_LOADED="1"

JAVA_HOME="<%= node['tomcat']['java_home'] %>"
JAVA_OPTS="<%= node['tomcat']['java_opts'] %>"

CATALINA_BASE="/usr/share/tomcat"
CATALINA_HOME="<%= node['tomcat']['catalina_home'] %>"
JASPER_HOME="/usr/share/tomcat"
CATALINA_TMPDIR="/var/cache/tomcat/temp"

TOMCAT_USER="<%= node['tomcat']['user'] %>"

SECURITY_MANAGER="false"

SHUTDOWN_WAIT="30"

SHUTDOWN_VERBOSE="false"

CATALINA_PID="/var/run/tomcat.pid"
  • Now update tomcat::config recipe as mentioned below
  • Path: /workspace/myapp/cookbooks/tomcat/recipes/config.rb
template node['tomcat']['config'] do
  source 'tomcat.conf.erb'
  owner node['tomcat']['user']
  group node['tomcat']['group']
  mode '0644'
  action :create
  notifies :restart, "service[#{node['tomcat']['service']}]", :delayed
end

  • Apply using kitchen converge

  • Now change the values of JAVA_OPTS in attribute file and then apply again for verifying the changes using template and attribute.

  • Also verify using kitchen login and run ps auwwx command.