atmos-vendoring

Atmos Component Vendoring

Vendoring copies external components, stacks, and other artifacts into your repository. This gives you full control over when and how dependencies change, with visibility through git diff, an immutable audit trail, and the ability to apply emergency patches without waiting for upstream releases.

Why Vendor

Terraform root modules must exist locally -- they cannot be pulled from remote sources at runtime the way child modules can. Vendoring makes this explicit: you copy the code once, commit it, and control when updates happen. This provides:

• Visibility: See actual code changes via git diff, not just version bumps.
• Audit trail: Every update is a commit with full history for compliance.
• Emergency agility: Patch vulnerabilities immediately without waiting for upstream.
• Developer experience: Full IDE navigation, grep across all code, better onboarding.
• Deployment reliability: No network dependencies during terraform apply.

Types of Vendoring

Atmos supports two approaches:

1. Vendor Configuration (vendor.yaml): A centralized manifest listing all dependencies. This is the recommended approach.
2. Component Manifest (component.yaml): A per-component manifest placed inside the component directory. This is the legacy approach.

vendor.yaml Manifest Format

The vendor.yaml file is a Kubernetes-style YAML configuration placed in the repository root (or the directory from which atmos vendor pull is executed):

apiVersion: atmos/v1
kind: AtmosVendorConfig
metadata:
  name: my-vendor-config
  description: Atmos vendoring manifest for ACME infrastructure
spec:
  imports:
    - "vendor/networking"
    - "vendor/security"

  sources:
    - component: "vpc"
      source: "github.com/cloudposse-terraform-components/aws-vpc.git?ref={{.Version}}"
      version: "1.398.0"
      targets:
        - "components/terraform/vpc"
      included_paths:
        - "**/*.tf"
        - "**/*.tfvars"
        - "**/*.md"
      excluded_paths:
        - "**/test/**"
      tags:
        - networking

    - component: "eks-cluster"
      source: "github.com/cloudposse-terraform-components/aws-eks-cluster.git?ref={{.Version}}"
      version: "2.15.0"
      targets:
        - "components/terraform/eks/cluster"
      tags:
        - compute

Top-Level Fields

• apiVersion: Always atmos/v1.
• kind: Always AtmosVendorConfig.
• metadata.name: Optional name for the vendor configuration.
• metadata.description: Optional description.
• spec.imports: List of additional vendor manifests to import (supports hierarchical imports and glob patterns).
• spec.sources: List of source definitions for components and artifacts to vendor.

Source Configuration

Each entry in spec.sources defines one component or artifact to vendor.

Source Fields

sources:
  - component: "vpc"
    source: "github.com/org/repo.git//path?ref={{.Version}}"
    version: "1.0.0"
    targets:
      - "components/terraform/vpc"
    included_paths:
      - "**/*.tf"
    excluded_paths:
      - "**/test/**"
    tags:
      - networking
    retry:
      max_attempts: 3
      initial_delay: 1s
      backoff_strategy: exponential

• component (string, optional): Component name used for atmos vendor pull -c <component> to vendor a single component. Also available as {{ .Component }} template variable.
• source (string, required): URL or path to the source. Supports Git, S3, HTTP/HTTPS, OCI, and local paths. Use {{ .Version }} template to inject the version.
• version (string, optional): Version identifier substituted into {{ .Version }} in source and targets.
• targets (list of strings, required): Local paths where files will be placed. Supports Go templates ({{ .Component }}, {{ .Version }}). Relative paths are resolved from the vendor.yaml location or base_path.
• included_paths (list of strings, optional): POSIX-style glob patterns for files to include. If not specified, all files are included.
• excluded_paths (list of strings, optional): POSIX-style glob patterns for files to exclude.
• tags (list of strings, optional): Tags for selective vendoring with atmos vendor pull --tags <tag>.
• retry (object, optional): Retry configuration for transient network errors.

Template Parameters

The source and targets fields support Go templates with these variables:

• {{ .Component }}: Value of the component field.
• {{ .Version }}: Value of the version field.

Example with versioned targets:

sources:
  - component: "vpc"
    source: "github.com/cloudposse-terraform-components/aws-vpc.git?ref={{.Version}}"
    version: "1.398.0"
    targets:
      - "components/terraform/{{ .Component }}/{{ .Version }}"

All Sprig template functions are available. For example, extracting major.minor version:

targets:
  - "components/terraform/{{ .Component }}/{{ (first 2 (splitList \".\" .Version)) | join \".\" }}"

Source Types

Git Repositories

The most common source type. Supports GitHub, GitLab, Bitbucket, and any Git host:

# GitHub (implicit HTTPS, recommended)
source: "github.com/cloudposse-terraform-components/aws-vpc.git?ref={{.Version}}"

# GitHub with subdirectory
source: "github.com/cloudposse/terraform-aws-components.git//modules/vpc?ref={{.Version}}"

# Explicit Git protocol
source: "git::https://github.com/org/repo.git?ref={{.Version}}"

# SSH authentication
source: "git::ssh://git@github.com/org/private-repo.git?ref={{.Version}}"

# GitLab
source: "gitlab.com/group/project.git?ref={{.Version}}"

# Bitbucket
source: "bitbucket.org/owner/repo.git?ref={{.Version}}"

The // delimiter separates the repository URL from the subdirectory within the repository. For example, repo.git//modules/vpc extracts only the modules/vpc directory. Without //, Atmos downloads the entire repository root.

OCI Registries

Pull artifacts from OCI-compatible container registries:

# AWS ECR Public
source: "oci://public.ecr.aws/cloudposse/components/terraform/stable/aws/vpc:{{.Version}}"

# GitHub Container Registry
source: "oci://ghcr.io/cloudposse/components/vpc:{{.Version}}"

# Docker Hub
source: "oci://docker.io/library/nginx:alpine"

OCI authentication precedence:

1. Docker credentials from ~/.docker/config.json (highest)
2. Environment variables (GITHUB_TOKEN + GITHUB_ACTOR for ghcr.io)
3. Anonymous (for public images)

Amazon S3

source: "s3::https://s3.amazonaws.com/acme-configs/components/vpc.tar.gz"
source: "s3::https://s3-us-west-2.amazonaws.com/bucket/path/component.tar.gz"

Uses AWS credentials from the environment or AWS config files.

HTTP/HTTPS

# Download and extract archive
source: "https://example.com/components/vpc.tar.gz"

# Download single file
source: "https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf"

Local Paths

# Relative to vendor.yaml location
source: "../shared-components/vpc"

# Absolute path
source: "/path/to/components/vpc"

# file:// URI
source: "file:///path/to/components/vpc"

Authentication

Automatic Token Injection

Atmos automatically injects tokens for private Git repositories:

Platform	Environment Variables	Default Enabled
GitHub	ATMOS_GITHUB_TOKEN or GITHUB_TOKEN	Yes
GitLab	ATMOS_GITLAB_TOKEN or GITLAB_TOKEN	No
Bitbucket	ATMOS_BITBUCKET_TOKEN or BITBUCKET_TOKEN	No

Enable GitLab/Bitbucket in atmos.yaml:

settings:
  inject_gitlab_token: true
  inject_bitbucket_token: true

SSH Authentication

source: "git@github.com:owner/private-repo.git?ref=v1.0.0"
source: "git@github.com:owner/private-repo.git?ref=v1.0.0&sshkey=~/.ssh/custom_key"

Include/Exclude Patterns

Use POSIX-style glob patterns to control which files are vendored:

included_paths:
  - "**/*.tf"          # All Terraform files recursively
  - "**/*.tfvars"      # All tfvars files
  - "**/*.md"          # All markdown files

excluded_paths:
  - "**/test/**"       # Exclude test directories
  - "**/*.yaml"        # Exclude YAML files
  - "**/examples/**"   # Exclude examples

Glob pattern syntax:

• * matches any characters within a single path segment.
• ** matches across multiple path segments recursively.
• ? matches exactly one character.
• [abc] matches any single character in the set.
• {a,b,c} matches any of the comma-separated patterns.

If included_paths is not specified, all files are included (minus any excluded_paths).

Imports in Vendor Manifests

Split the vendor.yaml into smaller files for maintainability:

# vendor.yaml
apiVersion: atmos/v1
kind: AtmosVendorConfig
spec:
  imports:
    - "vendor/networking"
    - "vendor/compute"
    - "vendor/security"
    - "vendor/**/*"           # Glob pattern: import all manifests recursively

Each imported file is a full AtmosVendorConfig manifest. Hierarchical imports are supported -- one manifest can import another, which imports another, etc. Import paths support glob patterns (*, **, ?, {a,b}).

Component Manifest (Legacy)

The legacy approach uses a component.yaml file inside the component directory:

# components/terraform/vpc/component.yaml
apiVersion: atmos/v1
kind: ComponentVendorConfig
metadata:
  name: vpc-vendor-config
  description: Vendoring config for VPC component
spec:
  source:
    uri: github.com/cloudposse/terraform-aws-components.git//modules/vpc?ref={{.Version}}
    version: 1.398.0
    included_paths:
      - "**/*.tf"
      - "**/*.md"
    excluded_paths:
      - "**/context.tf"
  mixins:
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf
      filename: context.tf

Mixins (Legacy)

Mixins download additional files and overlay them on the vendored component. They are processed after the main source is downloaded, and they can overwrite source files with the same filename:

spec:
  mixins:
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf
      filename: context.tf
    - uri: https://example.com/terraform/custom-providers.tf
      version: 1.0.0
      filename: custom-providers.tf

Mixin fields:

• uri: URL to download (supports all go-getter protocols).
• filename: Local filename in the component directory.
• version: Optional version for {{ .Version }} substitution in the URI.

atmos vendor pull Command

# Vendor all sources from vendor.yaml
atmos vendor pull

# Vendor all sources (explicit flag)
atmos vendor pull --everything

# Vendor a specific component
atmos vendor pull -c vpc
atmos vendor pull --component eks-cluster

# Vendor by tags
atmos vendor pull --tags networking
atmos vendor pull --tags networking,compute

Version Pinning

Pin versions by default in your vendor manifest for reproducible builds:

sources:
  - component: "vpc"
    source: "github.com/cloudposse-terraform-components/aws-vpc.git?ref={{.Version}}"
    version: "1.398.0"       # Pinned to specific tag
    targets:
      - "components/terraform/vpc"

For Git sources, use ?ref= with a specific tag or commit SHA for reproducible builds. Branch names like main point to a moving target and should only be used intentionally for development workflows, not for production vendoring.

Vendoring and Version Management Patterns

Vendoring works with several version management strategies:

Single Version (Simplest)

sources:
  - component: "vpc"
    version: "1.398.0"
    targets:
      - "components/terraform/vpc"

All environments use the same vendored version. Updates are atomic.

Folder-Based Versioning

sources:
  - component: "vpc"
    version: "1.398.0"
    targets:
      - "components/terraform/vpc/{{ .Version }}"

Multiple versions coexist. Stacks reference specific versions via metadata.component.

Major.Minor Versioning

sources:
  - component: "vpc"
    version: "1.398.0"
    targets:
      - "components/terraform/vpc/{{ (first 2 (splitList \".\" .Version)) | join \".\" }}"

Groups by major.minor version (e.g., vpc/1.398/).

Best Practices

1. Use vendor.yaml (not component.yaml): The centralized manifest is easier to maintain and provides a single view of all dependencies.
2. Pin versions by default: Use exact version tags or commit SHAs whenever possible. Use branch names only as an explicit exception when pinning is impractical.
3. Review changes via git diff: After running atmos vendor pull, review the diff before committing.
4. Use tags for selective vendoring: Tag sources by layer (networking, compute, security) for partial updates.
5. Automate with CI/CD: Set up GitHub Actions to periodically run atmos vendor pull and open PRs with changes.
6. Include only what you need: Use included_paths and excluded_paths to avoid vendoring test files, examples, and other unnecessary artifacts.
7. Use retry for flaky networks: Configure retry with exponential backoff for CI/CD environments.

References

• references/vendor-manifest.md -- Complete vendor.yaml schema reference, all source type fields, URL syntax