DevOps Classroomnotes 26/Dec/2021

Activity 3: Create a ntier architecture in Azure contd

• So we need to create a database
• Manually creating a database
  
  
  
  
• While creating a database we need to provide
• database details
• server details
• credentials
• size
• Network endpoints
  
• Lets create a sql server Refer Here
• Lets create an azure sql database Refer Here
• Now apply the configuration. Refer Here for the changes done and check the resources in the resource group
  
• Now lets add a vnet network rule Refer Here and firewall rule Refer Here
• Lets try to use the following conditional expression to create a service endpoint for db-1 subnet

var.subnet_names[count.index] == "db-1"? ["Microsoft.sql"]: []

• Refer Here for the changes done.

Terraform plan

• All these days we were executing terraform apply to create infrastructure
• Terraform apply command internally creates a plan and then executes the plan
• We can explicity create a plan terraform plan -out <filename> and then terraform apply <filename>

Terraform Provisioners

• Terraform provisioners can execute specific actions on the local machine or on the remote machine in order to prepare server or other infrastructure objects.
• If you are using local machine provisioners we need not establish any connections, but if we are using remote machine provisioners we need connections
• To specify connections for remote machines terraform has a connection block Refer Here for the official docs
• Lets try to use remote-exec connection to execute a inline script on the linux server
• Terraform provisioner written with in resource will be executed only when that resource is created.
• Solution 1: is to taint the resource i.e. mark the resource for recreation.
  
• Resource can be marked to taint by execution terraform taint <resourcetype>.<resourcename>
  
• Now if we execute terraform apply the resource will be destroyed and recreated.
• Execute Terraform apply
  
  
• Taint is designed to recreate the resource when you observe mismatches
• Note: before apply command is executed if you want to undo taint terraform untaint <resourcetype>.<resourcename>
• This approach will execute the script only once while creation.
• Now lets assume you have written a shell script for deploying application & whenever you execute terraform apply you want to do provisioning as we might be deploying the new version of the application generated from recent build.
• Refer Here for the changes
• Solution 2: Use Terraform null resource in null provider.
• The null resource will be executed every time you execute apply command. Refer Here for null resource documentation
• Refer Here for the changes done to include the null provisioner
• Note we have used build_id as trigger, so whenever build_id changes the terraform will executed the provisioner

terraform apply -var "build_id=2" -auto-approve