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gh-action_cache

Adaptive cache action that automatically chooses the appropriate caching backend based on repository visibility and ownership.

  • Automatically uses GitHub Actions cache for public repositories
  • Uses SonarSource S3 cache for private/internal SonarSource repositories
  • Seamless API compatibility with standard GitHub Actions cache
  • Supports all standard cache inputs and outputs
  • Automatic repository visibility detection

Requirements

  • jq (used by the cache key preparation script)
  • id-token: write permission (required for OIDC authentication with S3 backend)

Development

Prerequisites

  • Node.js 20+
  • npm

Install dependencies

npm install

Run tests

npm test              # single run
npm run test:watch    # watch mode

Build

The JS sub-actions (credential-setup, credential-guard) are bundled with @vercel/ncc into self-contained dist files. Rebuild after changing TypeScript source:

npm run build         # build all sub-actions
npm run build:setup   # build credential-setup only
npm run build:guard-main  # build credential-guard main only
npm run build:guard-post  # build credential-guard post only

Bundled output goes to credential-setup/dist/ and credential-guard/dist/. These must be committed since GitHub Actions runs them directly.

Usage

- uses: SonarSource/gh-action_cache@v1
  with:
    path: |
      ~/.cache/pip
      ~/.cache/maven
    key: cache-${{ runner.os }}-${{ hashFiles('**/requirements.txt', '**/pom.xml') }}
    restore-keys: cache-${{ runner.os }}-

Inputs

Input Description Required Default
path Files, directories, and wildcard patterns to cache Yes
key Explicit key for restoring and saving cache Yes
restore-keys Ordered list of prefix-matched keys for fallback No
fallback-to-default-branch Automatically add a fallback restore key pointing to the default branch cache (S3 backend only). Disable if you want strict branch isolation. No true
fallback-branch Optional maintenance branch for fallback restore keys (pattern: branch-*, S3 backend only). If not set, the repository default branch is used. No
environment Environment to use (dev or prod, S3 backend only) No prod
upload-chunk-size Chunk size for large file uploads (bytes) No
enableCrossOsArchive Enable cross-OS cache compatibility No false
fail-on-cache-miss Fail workflow if cache entry not found No false
lookup-only Only check cache existence without downloading No false
backend Force specific backend: github or s3. Takes priority over CACHE_BACKEND env var and auto-detection. No

Backend Selection

The cache backend is determined in the following priority order:

  1. inputs.backend — explicit input in the action step (github or s3)
  2. CACHE_BACKEND environment variable — set at the job or workflow level (github or s3)
  3. Repository visibility — github for public repos, s3 for private/internal repos

The CACHE_BACKEND env var is useful when the cache action is called indirectly through a composite action and you cannot set the backend input directly:

jobs:
  build:
    env:
      CACHE_BACKEND: s3   # forces S3 for all cache steps, including those in reusable actions
    steps:
      - uses: SonarSource/some-other-action@v1  # internally calls gh-action_cache

Outputs

Output Description
cache-hit Boolean indicating exact match for primary key

S3 Cache Action

A GitHub Action that provides branch-specific caching on AWS S3 with intelligent fallback to default branch cache entries.

Features

  • Branch-specific caching: Cache entries are prefixed with GITHUB_HEAD_REF for granular permissions
  • Intelligent fallback: Feature branches can fall back to default branch cache when no branch-specific cache exists
  • S3 storage: Leverages AWS S3 for reliable, scalable cache storage
  • AWS Cognito authentication: Secure authentication using GitHub Actions OIDC tokens
  • Compatible with actions/cache: Drop-in replacement with same interface

How Restore Keys Work

Cache Key Resolution Order

The action searches for cache entries in this order:

  1. Primary key: ${BRANCH_NAME}/${key}
  2. Branch-specific restore keys: ${BRANCH_NAME}/${restore-key} (for each restore key provided)
  3. Default branch fallbacks (when fallback-to-default-branch: true, the default):
    • If restore-keys are provided: refs/heads/${DEFAULT_BRANCH}/${restore-key} for each restore key
    • If no restore-keys are provided: refs/heads/${DEFAULT_BRANCH}/${key} (exact-match fallback)

Example — with restore-keys

- uses: SonarSource/gh-action_cache@v1
  with:
    path: ~/.npm
    key: node-${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
    restore-keys: node-${{ runner.os }}-

For a feature branch feature/new-ui, this will search for:

  1. feature/new-ui/node-linux-abc123... (exact match)
  2. feature/new-ui/node-linux- (branch-specific partial match)
  3. refs/heads/main/node-linux- (default branch fallback, assuming main is the repository's default branch)

Example — without restore-keys

- uses: SonarSource/gh-action_cache@v1
  with:
    path: ~/.npm
    key: node-${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}

For a feature branch feature/new-ui, this will search for:

  1. feature/new-ui/node-linux-abc123... (exact match)
  2. refs/heads/main/node-linux-abc123... (exact-match fallback on default branch)

To disable the automatic default branch fallback:

- uses: SonarSource/gh-action_cache@v1
  with:
    path: ~/.npm
    key: node-${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
    fallback-to-default-branch: false

Key Differences from Standard Cache Action

  • Automatic default branch fallback: By default, feature branches fall back to the default branch cache when no branch-specific entry exists
  • Dynamic default branch detection: The action detects your default branch using the GitHub API and uses it for fallback
  • Branch isolation: Each branch maintains its own cache namespace, preventing cross-branch cache pollution

Environment Configuration

The action supports two environments:

  • dev: Development environment with development S3 bucket
  • prod: Production environment with production S3 bucket (default)

Each environment has its own preconfigured S3 bucket and AWS Cognito pool for isolation and security.

Security

  • Uses GitHub Actions OIDC tokens for secure authentication
  • No long-lived AWS credentials required
  • Branch-specific paths provide isolation between branches

AWS Credential Isolation

This action uses a JS-based credential guard to ensure cache operations work correctly even when other steps in your workflow configure different AWS credentials.

How it works:

  1. credential-setup obtains temporary AWS credentials via GitHub OIDC + Cognito
  2. Credentials are saved to a protected temp file and passed to the cache step via outputs
  3. The cache restore step uses step-level env: from outputs — isolated from GITHUB_ENV
  4. credential-guard post-step re-exports credentials to GITHUB_ENV for cache save (LIFO ordering)

This protects against:

  • aws-actions/configure-aws-credentials overwriting credentials mid-job
  • aws-actions/configure-aws-credentials cleanup clearing credentials
  • Any step writing to GITHUB_ENV with different AWS credential values
  • Pre-existing AWS_PROFILE or AWS_DEFAULT_PROFILE in the environment
  • Users configuring AWS credentials before or after the cache action

Works regardless of credential ordering — you can configure your AWS credentials before or after the cache action:

jobs:
  build:
    steps:
      # Your own AWS authentication — order does not matter
      - uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::123456789:role/my-role
          aws-region: us-east-1

      # Cache action authenticates independently via OIDC + Cognito
      - uses: SonarSource/gh-action-cache@v2
        with:
          path: ~/.cache
          key: my-cache-${{ hashFiles('**/lockfile') }}

      - run: aws s3 ls  # Uses YOUR credentials (cache never touches GITHUB_ENV)

      # Post-step: credential-guard restores cache creds, then cache saves!

Cleanup Policy

The AWS S3 bucket lifecycle rules apply to delete the old files. The content from default branches expires in 60 days and for feature branches in 30 days.

Cache Cleanup

List or delete S3 cache entries for your repository without waiting for the 30-day lifecycle expiry.

Setup

Add a cleanup workflow to your repository (must be on the default branch):

# .github/workflows/cleanup-cache.yml
name: Cleanup S3 Cache

on:
  workflow_dispatch:
    inputs:
      branch:
        description: "Branch name (e.g., 'feature/my-branch'). Leave empty to list all entries."
        required: false
        type: string
        default: ""
      key:
        description: "Cache key prefix (e.g., 'sccache-Linux-')"
        required: false
        type: string
        default: ""
      dry-run:
        description: "Preview deletions without executing them"
        required: false
        type: boolean
        default: true

jobs:
  cleanup:
    runs-on: sonar-xs
    permissions:
      id-token: write
      contents: read
    steps:
      - uses: SonarSource/gh-action_cache/cleanup@v1
        with:
          branch: ${{ inputs.branch }}
          key: ${{ inputs.key }}
          dry-run: ${{ inputs.dry-run }}

Important: The cleanup workflow must be dispatched from a default/protected branch (e.g., main or master). This is required by the IAM policy for cross-branch cache deletion permissions.

Modes of Operation

Scenario Branch Key Dry-run
List all cache entries (empty) (empty) n/a
Preview what would be deleted feature/my-branch (optional) true
Delete cache for a branch feature/my-branch (optional) false
Delete key for given branch feature/my-branch sccache-Linux- false
Delete key across all branches (empty) sccache-Linux- false

Running via GitHub CLI

# List all cache entries for your repo
gh workflow run cleanup-cache.yml

# Preview deletions for a branch
gh workflow run cleanup-cache.yml -f branch="feature/my-branch" -f dry-run=true

# Delete all cache for a branch
gh workflow run cleanup-cache.yml -f branch="feature/my-branch" -f dry-run=false

# Delete specific cache key on a branch
gh workflow run cleanup-cache.yml -f branch="feature/my-branch" -f key="sccache-Linux-" -f dry-run=false