lifecycle

expected time	requirements
60 minutes	A computer with Terraform installed, terraform knowledge.

Goal: Be able to decide when to use the lifecycle meta argument and implement it.

Explanation

In some situations, Terraform needs to destroy and create a resource on changes. This means services may be interrupted. the lifecycle meta argument can prevent this.

Be aware that you need to prevent conflicts in names of resources, ports, and likely other parameters.

This type of deployment is ofter referred to as blue-green deployment.

Howto

See this Docker demo or this local-file demo

Assignment

• Go back to the Azure container groups repository, clone the code to your computer.
• Add a variables.tf to define a variable like deployment or so.
• Introduce the lifecycle meta argument to main.tf
• Change the azurerm_container_group.example.name to use the variable defined in variables.tf.
• Change the azurerm_container_group.example.dns_name_label to use the variable defined in variables.tf.
• Run the deployment and add -var="deployment=1".
• Run the deployment and add -var="deployment=2".
• Run the deployment and add -var="deployment=1".

Questions

1. Was the service interrupted during the deployments?
2. The deployment resulted in exposing a new IP address, how could you use this mechanism to make an uninterrupted deloyment?
3. How much time was saved in the below example?

azurerm_container_group.example: Creating...
azurerm_container_group.example: Still creating... [10s elapsed]
...
azurerm_container_group.example: Still creating... [1m10s elapsed]
azurerm_container_group.example: Creation complete after 1m16s [id=/subscriptions/27c6a60b-0aed-4e75-a7ea-f5cf2e49f89e/resourceGroups/example-resources/providers/Microsoft.ContainerInstance/containerGroups/example-continst-2]
azurerm_container_group.example: Destroying... [id=/subscriptions/27c6a60b-0aed-4e75-a7ea-f5cf2e49f89e/resourceGroups/example-resources/providers/Microsoft.ContainerInstance/containerGroups/example-continst]
azurerm_container_group.example: Still destroying... [id=/subscriptions/27c6a60b-0aed-4e75-a7ea-...tance/containerGroups/example-continst, 10s elapsed]
...
azurerm_container_group.example: Still destroying... [id=/subscriptions/27c6a60b-0aed-4e75-a7ea-...tance/containerGroups/example-continst, 1m10s elapsed]
azurerm_container_group.example: Destruction complete after 1m13s

Solution

• See this lifecycle branch.

Sources

• lifecycle