Key phases of migration

Assessment and planning

Inventory current infrastructure: Document all resources managed by CloudFormation.
Identify dependencies: Map out resource dependencies and relationships.
Evaluate complexity: Categorize resources based on complexity (simple, medium, complex).
Set objectives: Define goals for the migration, such as improved maintainability, reduced deployment time, or better provider support.

Skill building: Ensure the team knows Terraform, syntax, and best practices.
Tooling: Set up necessary tools, including Terraform CLI, AWS CLI, and version control systems like Git.
Environment setup: Prepare staging or a sandbox environment to test the migration process.
Set up an HCP Terraform account to take advantage of Terraform's advanced state management capabilities. Contact your account team for a trial account if needed.

Resource mapping: Ensure each property in CloudFormation is mapped to a corresponding Terraform resource.
Referencing resources: Use Terraform resource references (e.g. aws_vpc.my_vpc.id) instead of CloudFormation intrinsic functions (e.g., !Ref).
Modularization: Break down infrastructure into reusable Terraform modules. Please reference the HashiCorp Validated Design Operating Guide for Adoption under the sections Consumption Model and Terraform Workflow for more details and examples.
Incremental conversion: Start with less critical resources to build confidence and refine processes.
Configuration management: It is important to manage state files securely, consider using HCP Terraform to securely manage state files.

Static analysis: Use tools like terraform validate and terraform fmt to ensure code quality.
Plan and apply: Use terraform plan to preview changes and terraform apply to implement them.
Functional testing: Validate that resources are created and configured correctly.
- Reference:
  - Testing HashiCorp Terraform
  - Terraform Tests
Rollback strategy: Plan for rollbacks in case of issues, keeping CloudFormation stacks as a fallback.

Phased rollout: Deploy changes incrementally to reduce risk.
Monitoring and logging: Set up monitoring and logging to detect and troubleshoot issues.
Documentation: Document the new infrastructure setup and train relevant teams.

Introduction

Best practices