DevOps Classroom Series – 12/Sept/2020

Chef Infra Server Components

Creating Lab Environment

  • In this scenario
    • PROD: will be Ubuntu 18 machines from aws
    • UAT: Will be Ubuntu 18 machines from aws
    • QA: Will be Ubuntu 18 machine from azure
  • Upload qthms-app and qthms-db to the chef server
  • Now lets bootstrap manually all the nodes from workstation to nodes
  • Lets bootstrap chef server in the qa, uat and prod environments Preview
  • Lets try to come up with run_list for every node
QA : qthms-app::default,qthms-db::default

uat
	app: qthms-app::default
  
	db: qthms-db::default
  
prod:
	app: qthms-app::default
	
	db: qthms-db::default
  • In a large kind of deployment, managing run_lists is not effecient by add recipes to every node.
  • To manage this lets create two roles
    1. appserver
    2. dbserver
  • Roles can be created from chef-manage. Preview
  • But it is a good practice to have version control of your roles. so lets create roles files in chef-repo
  • For Roles Official docs Refer Here
  • Lets create two roles in the roles folder with the following content for
    1. appserver.rb
    name  'appserver'
    description 'This is qthms appserver'
    run_list 'qthms-app::default'
    
    1. dbserver.rb
    name  'dbserver'
    description 'This is qthms  dbserver'
    run_list 'qthms-db::default'
    
  • Now lets upload the roles to the chef server
knife role from file <path-to-rb>

Preview

  • Now lets edit run lists to have the roles in the run_list rather than recipes
  • Now the convergence time is 30 minutes for all the servers. Now lets learn how to change that
  • Client Configurations can be changed from client.rb file in the chef repo refer Here or easier way is to add the following cookbook to the run_list refer Here
# first approach
Chef::Config[:interval] = <seconds>

  • To do common configuration lets create a cookbook qt-general
  • In this cookbook lets add dependency of chef-client and set the attribute
default['chef_client']['interval']= '1800'
  • Now we need to add this recipe to all the nodes, we have roles, go and change the roles
  • For app servers the interval should be ‘3600’ seconds for db servers the convergence should be ‘7200’
  • The appserver.rb (role)
name  'appserver'
description 'This is qthms appserver'
run_list 'qt-general::default', 'qthms-app::default'
default_attributes(
    'chef_client' => {
        'interval' => '3600'
    }
)
  • Role db server
name  'dbserver'
description 'This is qthms dbserver'
run_list 'qt-general::default','qthms-db::default'
default_attributes(
    'chef_client' => {
        'interval' => '7200'
    }
)
  • Now we need to add a new version of the cookbook to include java ’11’ and also install apache server
  • Now make changes and after successful testing of this cookbook if you upload changes it will be applied to all servers in appserver role which is not what we want.
  • We want this changes to be applied only to QA, SO this is where environments come into play. \
  • Like Roles environments can be created from manage, inside chef-repo Refer Here
  • By default chef has a environment already called as _default Preview
  • Now lets create 3 environment files in environments folder in chef repo
    • qa.rb
    • uat.rb
    • prod.rb
  • Refer to git for these files
  • Lets upload the environments
knife environment from file <path-to-env>

Preview Preview

  • Lets apply environments to the nodes Preview

  • Now upload the cookbook Preview

  • Verify the QA Environment Preview

  • Verify in other Environment Preview

  • Now we have multiple places where we define attributes

    • recipe
    • attribute file
    • roles
    • environments
  • Lets understand what gets applied.

  • Chef has an extra layer which is attribute types

    • default
    • force_default
    • normal
    • override
    • force_override
    • automatic
  • We have 4 different places and six different types where attributes can be defined

  • Chef follows the following table for precedence Preview

  • Refer Here for offical docs

  • Note: GitHub Link Refer Here

Next Steps

  • How to deal sensitive Content in chef (data bags)
  • How to avoid manual bootstrapping
  • What is Chef Automate
  • How to use chef for managing infra in AWS (OpsWorks) & Azure (VM Extensions)
  • Exercises

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