Terraform Provisioning

• Provisioners can be used to model specific actions on the local machine or on a remote machine in order to prepare server or other infrastructure objects at scale.
• Concept of provisioning
  
• Provisioner types:
  • file
  • local-exec
  • remote-exec
  • chef
  • salt
  • puppet
• Refer Here

Activity: Lets install the following on the web vm

• Lets install apache server

sudo apt update
sudo apt install apache2 -y

• Lets do this in Azure (/AWS)
• Lets create connection
• Refer Here for the changes done to install apache2 on web vm and conditionally create app and db servers
• Situation1: To get the public ip from vm, we had to go to azure portal. Refer Here for the output documentation. Refer Here for the changes done
  
• Situation 2: We need to change the script and execute the installation of some other software
  • The VM is already created
  • Lets change the script and rexecute
    
  • The change in script of provisioning is not considered as change
    
• Solution 1 to above problem:
  • Whenever you change any thing in script, recreate the virtual machine
  • We need to mark virtual machine for deletion during next apply this is referred as taint in terraform.
  • Lets taint the vm and execute apply
    
    
    
    
• Solution 2: Execute provisioning all the times when you execute apply
  • But terraform executes provisioner only when resource is created.
  • Terraform has a resource called as null resource which it tries to create during apply and we run the provisioner over there
    
  • One option is to mark the null resource for taint before apply (or when the provisioining needs to happen)
  • other option is to use triggers
    
    
  • Refer Here for the changes done.
• Exercise:
  • For the people aware of ansible try to install apache server from ansible playbook in terraform provisioning
  • Create the provisioner to install tomcat on appserver
• Made some subtle changes and we have the following output, Refer Here for the changes
  

Activity: Create a reusable terraform configuration to create ntier

• Terraform modules can help in creating reusable configuration Refer Here

Situation 1: Lets try to use existing modules

• A lot of opensource contributers create reusable terraform configuration as modules and host them on various sources.
• Terraform registry is the popular one
• Lets try to use a module created by someone to create a network in Azure Refer Herefor the network module
• Refer Here for the changeset
  
• The source code of the module which we have used is Refer Here
• It is exactly similar what we have been developing
• A Module is a collection of terraform files
  • input variables become arguments
  • output variables become attributes of the module

Situation 2: Lets try to create module from our configuration

• Refer Here for the module which we added
• Structure recommendations of module from terraform Refer Here
• We have used the source which is present in the same machine and we can use this source to access any drive (local/network) to gain access to reusable modules

Situation 3: How to make modules to be used by all of our team members

• One way is make them available on network file shares and access them
• We can use any of the module sources Refer Here
  
• Create a git repository for every module which devops team creates Refer Here
• for using module from git we have created the following changeset Refer Here
• Now execute init and apply