Introduction
In the fast-paced world of DevOps, efficiency is king. Terraform, HashiCorp’s popular infrastructure as code (IaC) tool, is widely used for automating the deployment of infrastructure. However, as your infrastructure grows in complexity, Terraform operations can slow down, affecting your deployment speed. Fortunately, Terraform supports caching plan files to speed up deployments. This tutorial will explore optimizing Terraform’s performance by caching plan files, offering both an introduction to newcomers and deep dives for experienced users.
Understanding Terraform Plan Files
Before delving into caching, let’s align on the basics. A Terraform plan file is the output of terraform plan, containing an execution plan that shows what Terraform intends to do without making any changes. Plan files are invaluable for understanding changes before applying them, and can be saved using the -out option.
terraform plan -out=plan.tfplan
This generates a file named plan.tfplan, which you can selectively apply with:
terraform apply "plan.tfplan"
The Role of Caching in Terraform
Caching in Terraform involves saving the plan file to skip regeneration for subsequent runs, speeding up operations by avoiding redundant computations. While Terraform does not inherently feature a cache command, you can implement caching through creative usage of its existing commands and external tooling.
Basic Terraform Caching Mechanism
To start simple, use a local filesystem path to save and reapply plan files. However, ensure changes to your configuration files or the targeted infrastructure are minimal, as plan files can rapidly become outdated.
terraform plan -out=cache/plan.tfplan
Later, you can reapply the same plan if no significant changes have occurred:
terraform apply "cache/plan.tfplan"
Advanced Terraform Caching: State Locking and Backend Support
Moving to more advanced caching mechanisms involves the use of remote backends and state locking. By leveraging a cloud storage service (e.g., S3 for AWS or Blob Storage for Azure) as a backend, you can store plan files remotely, enabling team members to access and apply them.
terraform {
backend "s3" {
bucket = "your-bucket-name"
key = "path/to/your/tfstate"
region = "your-region"
}
}
However, remote storage introduces the risk of simultaneous access, making state locking crucial to prevent conflicts. State locking ensures that only one operation can be performed at a time.
Using Terraform Cloud for Efficient Caching
Terraform Cloud provides built-in functionality for caching plan files, offering an even more streamlined experience. With Terraform Cloud, you can automate the caching process, leverage shared workspaces for team collaboration, and ensure security with state locking and encryption.
To use Terraform Cloud’s caching, simply configure your workspace settings and let the platform manage caching for you.
Automation and CI/CD Integration
Integrating Terraform caching into your Continuous Integration/Continuous Deployment (CI/CD) pipeline can significantly reduce deployment times. Most CI/CD tools allow you to cache files between runs. By caching the .terraform directory, you can reuse plan files, modules, and provider plugins.
# Example configuration snippet for GitLab CI
stages:
- plan
- apply
plan:
stage: plan
script:
- terraform plan -out=plan.tfplan
cache:
paths:
- .terraform
apply:
stage: apply
script:
- terraform apply "plan.tfplan"
cache:
paths:
- .terraform
Conclusion
Caching plan files in Terraform can dramatically speed up your deployment times. Starting with basic file system caching and moving towards advanced methods like remote state backends, state locking, and Terraform Cloud, you have a variety of options to optimize your Terraform operations. Always remember to handle cached plan files with caution, ensuring they’re updated as your infrastructure evolves. With thoughtful caching strategies, Terraform can become an even more powerful tool in your DevOps arsenal.
