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Zero-Config Terraform Provider Caching

· 2 min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

Atmos now automatically caches Terraform providers across all components, dramatically reducing terraform init times and network bandwidth. This feature is enabled by default with zero configuration required.

Why Provider Caching Matters​

In large Atmos projects with many components, each terraform init downloads the same providers repeatedly. For the AWS provider alone, this can mean downloading 300+ MB per component. With provider caching, Atmos downloads each provider version once and reuses it across all components.

How It Works​

When you run any Terraform command, Atmos automatically:

  1. Sets TF_PLUGIN_CACHE_DIR to ~/.cache/atmos/terraform/plugins
  2. Sets TF_PLUGIN_CACHE_MAY_BREAK_DEPENDENCY_LOCK_FILE=true (required by Terraform)

Terraform then downloads providers to this shared cache and creates symlinks in each component's .terraform directory.

Zero Configuration​

Provider caching works out of the box. Just upgrade Atmos and run your commands as usual:

atmos terraform init mycomponent -s dev

The first init downloads providers to the cache. Subsequent inits for other components reuse the cached providers instantly.

Configuration Options​

While caching works with no configuration, you can customize its behavior in atmos.yaml:

components:
  terraform:
    # Disable automatic caching (default: true)
    plugin_cache: false

    # Use a custom cache directory (default: ~/.cache/atmos/terraform/plugins)
    plugin_cache_dir: /shared/terraform/plugin-cache

Or via environment variables:

export ATMOS_COMPONENTS_TERRAFORM_PLUGIN_CACHE=false
export ATMOS_COMPONENTS_TERRAFORM_PLUGIN_CACHE_DIR=/custom/path

Respecting User Overrides​

If you already have TF_PLUGIN_CACHE_DIR set in your environment or in the env: section of atmos.yaml, Atmos respects your configuration and does not override it.

Cleaning the Cache​

To free disk space or force providers to be re-downloaded, use the new --cache flag:

# Clean the shared plugin cache
atmos terraform clean --cache

# Clean with force (no confirmation prompt)
atmos terraform clean --cache --force

Performance Impact​

In our testing with projects containing 50+ components:

  • First init: Same as before (downloads all providers)
  • Subsequent inits: 10-50x faster (symlinks from cache)
  • Disk savings: Significant reduction in duplicate provider binaries