DevOps Classroom Series – 20/Nov/2021

Chef Cookbooks With Chef Server

• Lets bootstrap two nodes to the hosted chef server
• Experiment:
  • Develop a simple cookbook with version 1.0.0 which prints this is version 1.0.0
  • use log resource Refer Here
  • Refer Here for the new cookbook added.
  • Now upload the recipe and this to the run_list of the ubuntunode1
  • Now lets login into ubuntu node 1 and manually force convergance
  • Now lets assume we are giving uploading a new version of the cookbook (experiment 1.0.0) and this should not apply to ubuntunode1. ubuntunode1 should work with experiment with version 1.0.0
  • Refer Here for the new version of cookbook
  • Upload the new version and now login into ubuntunode1 and manually force convergence
  • We need to have some kind of mechanism where we need to restrict the cookbook versions to be uploaded.
  • In Chef we can solve the problem with cookbook versions using Environments
  • Lets create three cookbooks
    • qtwebapp
      • default
      • configure
    • qtdbapp
      • default
      • configure
    • qtcommonapps
      • recipes:
        • default
        • special
  • Now lets assume we have three categories of nodes
    • We have db servers
    • We have web servers
    • For testing we have some nodes where we install both web and db on same node
  • To do this we need to have the following run_lists
    • webserver => qtcommonapps::default, qtcommonapps::special, qtwebapp::default, qtwebapp::configure
    • db server => qtcommonapps::default, qtdbapp::default, qtdbapp::configure
    • web+dbserver => qtcommonapps::default, qtcommonapps::special, qtwebapp::default, qtwebapp::configure,qtdbapp::default, qtdbapp::configure
  • When we have lot of servers to deal with creating run_lists like shown above does it make sense?
  • We need to have some kind of a solution to manage run_lists effectively
  • In Chef we can solve the problem with managing run_lists using Roles

Chef Environments

• An environment is a way to map organization real-life workflow.
• With Environments we can define the below and attach environment to the node
  • cookbook versions applicable
  • attributes
• Chef has a default environment already defined _default where there are no restrictions,
• We can create environments like shown below and attach it to the node
  • DEV
  • QA
  • STAGING
  • PROD
• There are two ways of creating environments,
  • Using Chef Managment console: Easy but not recommended
  • Create a file in the chef-repo and upload: In this we are having a file which represents environment and we can easily track all the changes done to a file which represents environment as we version control it.
• Refer Here for the official documentation
• Refer Here for the changeset.
• Now lets try to upload environments knife environment from file Refer Here for documentation
• Now lets apply the same runlist of experiment to ubuntunode1 and ubuntunode2.
• Now lets make the ubuntunode1 environment => dev and ubuntunode2 environment => prod
• converge results of ubuntunode1
• converge results of ubuntunode2

Roles

• Role consists of run_list and attributes
• To the nodes run_list we can add roles directly instead of individual recipes
• To do this we need to have the following run_lists
  • webserver => qtcommonapps::default, qtcommonapps::special, qtwebapp::default, qtwebapp::configure
  • db server => qtcommonapps::default, qtdbapp::default, qtdbapp::configure
  • web+dbserver => qtcommonapps::default, qtcommonapps::special, qtwebapp::default, qtwebapp::configure,qtdbapp::default, qtdbapp::configure
• Now first lets upload qtcommonapps, qtwebapps and qtdbapss. Refer Here for the changeset with all the three cookbooks
• Now lets create the roles, As environments we can create using console and from file. Refer Here for the official docs
• Refer Here for the changeset
• Refer Here for the command to upload the roles to chef server
• Now lets add the roles
  • webserver+dbserver to the run_list of ubuntunode1
  • webserver to the run_list of ubuntunode2
• Now lets manually force the convergence
  • ubuntu node1: => webserver+dbserver
  • ubuntu node2: => webserver