Lets Make the templates which we have developed reusable

• Reusability is essential as we follow principle DRY (Dont Repeat Yourself)
• In Terraform, if we need reusability we need to create modules.

Activity: Lets use module which is developed by some one else

• Terraform has lot of modules developed by communities and terraform stores them in terraform registry Refer Here
• Lets create a vpc from terraform module Refer Here
• Refer Here for the sample module used for terraform registry

What are the things required to make our template reusable

• Outputs: Refer Here
• Lets add some outputs to Azure network
• Added outputs section. Refer Here for outputs.tf
  
• We have made a small change to display subnet count. Refer Here for the changes
  
• Now destory whatever is created
• Now to make this as a module,
  • Module is not supposed to have provider
  • Modules generally will not have tfvars as this is something that belongs to template
• Refer Here for the module usage syntax
• We have created a demo to use the module from local path Refer Here for the changes
  
• Now lets try creating the same from differnt source
  • git git::https://github.com/asquarezone/ntier-azure-vnet.git
  • github github.com/asquarezone/ntier-azure-vnet
    
• Refer Here for the changes to pick the module from git repository
• We can also use other sources Refer Here

Datasource

• Datasource help in fetching the information about some resources in the provider.
• Lets try to query the aws to get the vpc id of the default vpc
• Refer Here for the usage syntax of datasources
• Refer Here for the datasource of aws vpc
• The following changeset is used to pull the defult vpc id of mumbai region and subnetids of any vpc from az ap-south-1a Refer Here
  
• Now lets add datasource to get all the resources of a specfic type (vnet) in azure. Refer Here for the datasource
• Refer Here for the changes.