Demystifying Terraform Workflow Lifecycle: Navigating Infrastructure as Code Management

In Infrastructure as Code (IaC), Terraform is a leading tool for automating infrastructure provisioning and management. Its declarative language and robust ecosystem enable users to define, plan, and manage infrastructure across various cloud providers. Terraform's workflow involves key commands: init, plan, validate, apply, and destroy, essential for an efficient setup.

Stages of the Terraform Resource Lifecycle

When you define a resource in Terraform, it goes through several stages:

1. Creation: When you run terraform apply, Terraform creates the resource as specified in your configuration. This process involves communicating with the cloud provider's API to provision the resource.

2. Modification: If changes are made to the resource configuration, Terraform can update the existing resource in place, if possible. If not, it may destroy the existing resource and create a new one based on the updated configuration.

3. Destruction: When a resource is removed from the configuration or explicitly destroyed using terraform destroy, Terraform will handle its removal from the infrastructure.

Lifecycle of Terraform Commands

1. Terraform Init

terraform init

The first step in working with Terraform is to initialize your working directory. The terraform init command is responsible for initializing the configuration files and setting up the working environment.

• What happens?

  • It downloads the necessary provider plugins for the specified cloud services. Initializes the backend (where Terraform will store the state of your infrastructure).

  • Configures the local directory for use with Terraform.

    
    

2. Terraform Plan

terraform plan

The terraform plan command is a critical step in Terraform’s lifecycle. It allows you to preview the changes Terraform will make to your infrastructure without actually applying them. Essentially, it provides a dry-run to validate if your configuration will behave as expected.

• What happens?

  • Terraform inspects the current state of your infrastructure (usually stored in a backend) and compares it with the desired state defined in your configuration files.

  • It then generates a list of actions it will take to reconcile any differences.

• When to use?

  • After modifying the configuration files and before applying the changes.

  • It’s a safeguard to ensure you’re making the intended changes.

3. Terraform Validate

terraform validate

The terraform validate command is designed to check the syntax and validity of the Terraform configuration files. It ensures that your configuration files are correctly written and free from syntax errors.

• What happens?

  • It checks for any structural issues in your .tf files.

  • It does not access any infrastructure or state but only validates the configuration's correctness.

• When to use?

  • Before running terraform plan or terraform apply.

  • It's a good practice to use it after editing your configuration files to catch errors early.

4. Terraform Apply

terraform apply

The terraform apply command is where the rubber meets the road. After reviewing the plan and validating the configuration, running terraform apply will actually apply the changes to your infrastructure.

• What happens?

  • Terraform will execute the planned actions, such as creating, modifying, or deleting resources, to match the desired state.

  • It updates the infrastructure and persists the new state in the backend.

• When to use?

  • After reviewing the plan and confirming that the proposed changes are correct.

5. Terraform Destroy

terraform destroy

When you no longer need the infrastructure, the terraform destroy command helps you clean up by removing all the resources defined in the Terraform configuration.

• What happens?

  • Terraform will go through the process of destroying all the infrastructure it has provisioned.

  • This step is useful for decommissioning environments, such as test or staging environments, to avoid unnecessary costs.

• When to use?

  • When you want to tear down the infrastructure after it’s no longer needed or after testing.

Summary of Terraform Workflow Lifecycle

1. Init: Initialize the working environment and download necessary provider plugins.

2. Validate: Ensure the configuration files are correctly structured and syntactically valid.

3. Plan: Preview the changes Terraform will make to the infrastructure based on the current state and the configuration.

4. Apply: Implement the changes to match the desired state of the infrastructure.

5. Destroy: Tear down the infrastructure when it's no longer needed.