Back-to-code Actions

Reusable composite actions for self-hosted ARC runners. Tool install + dep setup that leans on host-mounted download caches — zero network round-trips to GitHub cloud cache.

Why custom actions?

CI on self-hosted runners (ARC on k3s, dind mode):

Persistent host-path volumes for tool-cache, npm, composer, general .cache
tmpfs working dir (RAM-backed, fast I/O)
Limited network bandwidth

Standard actions/cache uploads/downloads to GitHub cloud. We skip entirely — package-manager download caches live on the runner node and persist across ephemeral pods. Install times: minutes → seconds.

Caching philosophy — download cache, not artifacts

These actions cache downloads, not build artifacts. Every job runs a fresh npm ci / composer install / pub get, populated from the warm download cache on the host volume. We do not tar node_modules / vendor / .dart_tool and skip install on cache hit.

Rationale (learned the hard way):

Postinstall scripts run every job → broken postinstalls surface on the PR that introduces them, not N PRs later when the cache finally misses.
npm workspaces nesting, transitive version conflicts, and similar lockfile quirks can't produce a partial cached tree — there's nothing to go stale.
A fresh npm ci against a warm ~/.npm is fast (seconds). The tar-restore savings weren't worth the fragility.

All workflows must use these actions for dep setup. Never use actions/cache, actions/setup-node with cache: 'npm', or manual npm ci/composer install/pub get — go through the composite actions so env + cache paths stay consistent.

Available actions

setup-node

Installs Node.js, runs npm ci against the host-mounted ~/.npm download cache.

- uses: Back-to-code/actions/setup-node@v1

Input	Default	Description
`node-version`	`22`	Node.js version
`working-directory`	`.`	Directory with `package-lock.json`

npm ci runs every invocation. Fast on warm ~/.npm.

setup-php

Switches PHP version, runs composer install against the host-mounted ~/.composer/cache download cache.

- uses: Back-to-code/actions/setup-php@v1
  with:
    working-directory: apps/api

Input	Default	Description
`php-version`	`8.4`	PHP version (must be in runner image)
`working-directory`	`.`	Directory with `composer.json`
`composer-flags`	`''`	Extra flags for `composer install`

PHP versions pre-installed via ondrej/php PPA. Action uses update-alternatives to switch — no download. Composer runs w/ XDEBUG_MODE=off for speed. composer install runs every invocation.

setup-go

Installs Go, caches module downloads locally.

- uses: Back-to-code/actions/setup-go@v1
  with:
    go-version: '1.26'

Input	Default	Description
`go-version`	`1.26`	Go version
`working-directory`	`.`	Directory with `go.sum`

Disables built-in actions/setup-go cloud cache. Caches ~/go/pkg/mod via local-cache (download cache of immutable module tarballs — safe to tar). Go build cache (~/.cache/go-build) persists via runner host-path volume mount. go mod download runs on miss.

setup-dart

Installs Dart SDK, runs dart pub get against the host-mounted ~/.pub-cache download cache.

- uses: Back-to-code/actions/setup-dart@v1

Input	Default	Description
`sdk`	`stable`	Dart SDK version
`working-directory`	`.`	Directory with `pubspec.lock`

dart pub get runs every invocation.

setup-flutter

Installs Flutter SDK, runs flutter pub get against the host-mounted ~/.pub-cache download cache.

- uses: Back-to-code/actions/setup-flutter@v1
  with:
    flutter-version: stable

Input	Default	Description
`flutter-version`	`stable`	Flutter version
`channel`	`stable`	Channel (stable, beta, master)
`working-directory`	`.`	Directory with `pubspec.lock`

flutter pub get runs every invocation.

Writing optimized workflows

Rule 1: Always use `runs-on: self-hosted`

All CI jobs on self-hosted runners. Never ubuntu-latest or GitHub-hosted for CI checks — no cached deps/tools.

Exception: deploy workflows may use ubuntu-latest for security (ephemeral, no persistent credentials).

Rule 2: Set concurrency groups

Every PR workflow must cancel in-progress runs on new push:

concurrency:
  group: ${{ github.workflow }}-${{ github.head_ref }}
  cancel-in-progress: true

Deploy workflows — never cancel in-progress, queue instead:

concurrency:
  group: deploy-production
  cancel-in-progress: false

Rule 3: Set timeout-minutes on every job

Default timeout 6 hours. Hung job silently burns runner capacity. Set ~2x expected duration:

jobs:
  lint:
    timeout-minutes: 10    # Expected: ~5 min
  test:
    timeout-minutes: 15    # Expected: ~8 min

Rule 4: Use path filtering to skip irrelevant jobs

Use dorny/paths-filter@v3 at job level to skip when files unchanged:

jobs:
  changes:
    runs-on: self-hosted
    timeout-minutes: 5
    outputs:
      backend: ${{ steps.filter.outputs.backend }}
      frontend: ${{ steps.filter.outputs.frontend }}
    steps:
      - uses: dorny/paths-filter@v3
        id: filter
        with:
          filters: |
            backend:
              - 'src/api/**'
              - 'go.sum'
            frontend:
              - 'src/web/**'
              - 'package-lock.json'

  lint:
    needs: changes
    if: needs.changes.outputs.frontend == 'true'
    # ...

Never workflow-level paths: triggers — skips entire workflow → required status checks stay "Pending" forever.

Rule 5: Gate job for required checks

Skipped jobs don't satisfy required checks. Use gate job:

jobs:
  # ... all your conditional jobs ...

  ci-passed:
    name: CI Passed
    if: always()
    needs: [lint, test, build]  # List ALL conditional jobs
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
        run: exit 1

Branch protection: mark only CI Passed as required:

Skipped jobs (path filtering) → gate passes
Failed jobs → gate fails
Cancelled jobs → gate fails

Keep all CI jobs in one workflow file. Gate jobs only work within single workflow — needs: can't cross workflow boundaries. Split into separate files:

No single gate watching all jobs
Workflow-level paths: filters → skipped workflows → required checks "Pending" forever
Multiple gate jobs = more required checks to maintain

Use job-level path filtering (dorny/paths-filter) inside one workflow + one gate job. Only split for genuinely different triggers (PR checks vs deploy vs scheduled).

Rule 6: Service containers work in dind mode

Runners support services: containers. Docker images layer-cached on runner — repeated pulls near-instant.

jobs:
  test:
    runs-on: self-hosted
    services:
      mysql:
        image: mysql:8.0
        env:
          MYSQL_ROOT_PASSWORD: password
          MYSQL_DATABASE: testing
        ports:
          - 3306:3306
        options: >-
          --health-cmd="mysqladmin ping"
          --health-interval=10s
          --health-timeout=5s
          --health-retries=5
          --health-start-period=30s

Use --health-start-period for MySQL (10-25s init). Redis/PostgreSQL start faster.

Rule 7: Sparse checkout for monorepos

Job only needs part of repo → sparse checkout:

- uses: actions/checkout@v4
  with:
    sparse-checkout: |
      apps/api
      .github

Rule 8: Minimize permissions

Always declare minimum required:

permissions:
  contents: read

Add more only when needed (e.g., pull-requests: write for posting comments).

Rule 9: SHA-pin third-party actions

Pin every uses: to a full commit SHA with the version as a trailing comment. Applies to all suppliers, including ally-controlled (Back-to-code/actions/*) — moving tags can be re-pointed silently, SHA cannot.

- uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
- uses: Back-to-code/actions/setup-node@<sha> # v1
- uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3.0.2
- uses: github/codeql-action/upload-sarif@<sha> # v4

Why:

ISO 27001 A.5.21 requires commit-pinning for supply-chain integrity regardless of supplier trust.
Tag-pin (@v4) re-resolves on each run → upstream tag move (compromise or rewrite) flows in undetected.
SHA + version comment keeps Dependabot / human review readable.

Dependabot can manage SHA bumps:

# .github/dependabot.yml
version: 2
updates:
  - package-ecosystem: github-actions
    directory: /
    schedule:
      interval: weekly

The workflow examples below use moving tags (@v4, @v1) for readability. Real workflows must SHA-pin per Rule 9.

Complete workflow template

name: PR Checks

on:
  pull_request:

permissions:
  contents: read

concurrency:
  group: pr-checks-${{ github.head_ref }}
  cancel-in-progress: true

jobs:
  # ── Detect what changed ────────────────────────────────────────
  changes:
    name: Detect changes
    runs-on: self-hosted
    timeout-minutes: 5
    outputs:
      backend: ${{ steps.filter.outputs.backend }}
      frontend: ${{ steps.filter.outputs.frontend }}
    steps:
      - uses: dorny/paths-filter@v3
        id: filter
        with:
          filters: |
            backend:
              - 'src/api/**'
              - 'composer.lock'
            frontend:
              - 'src/web/**'
              - 'package-lock.json'

  # ── Frontend ───────────────────────────────────────────────────
  lint:
    name: ESLint
    needs: changes
    if: needs.changes.outputs.frontend == 'true'
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-node@v1
      - run: npm run lint

  typecheck:
    name: Type check
    needs: changes
    if: needs.changes.outputs.frontend == 'true'
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-node@v1
      - run: npx vue-tsc --noEmit

  test-frontend:
    name: Frontend tests
    needs: changes
    if: needs.changes.outputs.frontend == 'true'
    runs-on: self-hosted
    timeout-minutes: 15
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-node@v1
      - run: npm run test -- --coverage

  build:
    name: Build
    needs: changes
    if: needs.changes.outputs.frontend == 'true'
    runs-on: self-hosted
    timeout-minutes: 15
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-node@v1
      - run: npm run build
        env:
          NODE_OPTIONS: '--max-old-space-size=4096'

  # ── Backend ────────────────────────────────────────────────────
  test-backend:
    name: Backend tests
    needs: changes
    if: needs.changes.outputs.backend == 'true'
    runs-on: self-hosted
    timeout-minutes: 15
    services:
      mysql:
        image: mysql:8.0
        env:
          MYSQL_ROOT_PASSWORD: password
          MYSQL_DATABASE: testing
        ports:
          - 3306:3306
        options: >-
          --health-cmd="mysqladmin ping"
          --health-interval=10s
          --health-timeout=5s
          --health-retries=5
          --health-start-period=30s
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-php@v1
      - run: |
          cp .env.example .env
          php artisan key:generate
          php artisan migrate:fresh --force
        env:
          DB_HOST: 127.0.0.1
          DB_DATABASE: testing
          DB_USERNAME: root
          DB_PASSWORD: password
      - run: php vendor/bin/pest
        env:
          DB_HOST: 127.0.0.1
          DB_DATABASE: testing
          DB_USERNAME: root
          DB_PASSWORD: password

  php-style:
    name: PHP style
    needs: changes
    if: needs.changes.outputs.backend == 'true'
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-php@v1
      - run: composer run pint:ci

  # ── Gate ───────────────────────────────────────────────────────
  ci-passed:
    name: CI Passed
    if: always()
    needs: [lint, typecheck, test-frontend, build, test-backend, php-style]
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
        run: exit 1

Go project template

name: PR Checks

on:
  pull_request:

permissions:
  contents: read

concurrency:
  group: pr-checks-${{ github.head_ref }}
  cancel-in-progress: true

jobs:
  lint:
    name: Lint
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-go@v1
      - uses: golangci/golangci-lint-action@v6
        with:
          version: latest

  test:
    name: Test
    runs-on: self-hosted
    timeout-minutes: 15
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-go@v1
      - run: go test ./...

  build:
    name: Build
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-go@v1
      - run: go build ./...

  ci-passed:
    name: CI Passed
    if: always()
    needs: [lint, test, build]
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
        run: exit 1

Dart project template

name: PR Checks

on:
  pull_request:

permissions:
  contents: read

concurrency:
  group: pr-checks-${{ github.head_ref }}
  cancel-in-progress: true

jobs:
  analyze:
    name: Analyze
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-dart@v1
      - run: dart analyze

  test:
    name: Test
    runs-on: self-hosted
    timeout-minutes: 15
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-dart@v1
      - run: dart test

  ci-passed:
    name: CI Passed
    if: always()
    needs: [analyze, test]
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
        run: exit 1

Flutter project template

name: PR Checks

on:
  pull_request:

permissions:
  contents: read

concurrency:
  group: pr-checks-${{ github.head_ref }}
  cancel-in-progress: true

jobs:
  analyze:
    name: Analyze
    runs-on: self-hosted
    timeout-minutes: 10
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-flutter@v1
      - run: flutter analyze

  test:
    name: Test
    runs-on: self-hosted
    timeout-minutes: 15
    steps:
      - uses: actions/checkout@v4
      - uses: Back-to-code/actions/setup-flutter@v1
      - run: flutter test

  ci-passed:
    name: CI Passed
    if: always()
    needs: [analyze, test]
    runs-on: self-hosted
    timeout-minutes: 5
    steps:
      - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
        run: exit 1

Common mistakes

Mistake	Fix
`ubuntu-latest` for CI	`self-hosted` — cached deps, faster
Missing `concurrency` block	Add w/ `cancel-in-progress: true`
No `timeout-minutes`	Set on every job (~2x expected)
`actions/cache`	Use our setup actions (local cache)
`npm install`	`npm ci` (faster, deterministic)
Workflow-level `paths:` filter	`dorny/paths-filter` at job level
All jobs as required checks	Gate job pattern (only `CI Passed` required)
Missing health check on MySQL	Add `--health-start-period=30s`
`composer update` in CI	`composer install` (reads lockfile)
Default 90-day artifact retention	Set `retention-days: 3` or lower
Moving-tag pin (`@v4`)	SHA-pin + `# v4` comment (Rule 9)

Cache architecture

Host node (/opt/runner-cache/)
├── tool-cache/        → /opt/hostedtoolcache   (Node, Go, Dart, Flutter binaries)
├── npm/               → ~/.npm                  (npm download cache)
├── composer/          → ~/.composer/cache       (Composer download cache)
├── pub-cache/         → ~/.pub-cache            (Dart/Flutter pub download cache)
├── local-cache/       → ~/.cache                (general download caches — go-build, puppeteer, etc.)
└── docker/            → /var/lib/docker         (Docker layer cache for service containers)

Single-layer strategy: package-manager download caches live on host volumes. Every job installs fresh against a warm download cache.

Tool	Cache path	Mounted via
npm	`~/.npm`	dedicated `npm` volume
composer	`~/.composer/cache`	dedicated `composer` volume
dart / flutter	`~/.pub-cache`	dedicated `pub-cache` volume
go	`~/go/pkg/mod`	via `local-cache` action (download cache — immutable hashed tarballs)
puppeteer	`~/.cache/puppeteer`	`.cache` volume (usually unused — set `PUPPETEER_EXECUTABLE_PATH` to system chrome)

All persist across ephemeral runner pods via host-path volumes. Artifact directories (node_modules, vendor, .dart_tool) are never cached — they're reconstructed every job.

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Repository files navigation

Back-to-code Actions

Why custom actions?

Caching philosophy — download cache, not artifacts

Available actions

setup-node

setup-php

setup-go

setup-dart

setup-flutter

Writing optimized workflows

Rule 1: Always use `runs-on: self-hosted`

Rule 2: Set concurrency groups

Rule 3: Set timeout-minutes on every job

Rule 4: Use path filtering to skip irrelevant jobs

Rule 5: Gate job for required checks

Rule 6: Service containers work in dind mode

Rule 7: Sparse checkout for monorepos

Rule 8: Minimize permissions

Rule 9: SHA-pin third-party actions

Complete workflow template

Go project template

Dart project template

Flutter project template

Common mistakes

Cache architecture

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Name		Name	Last commit message	Last commit date
Latest commit History 22 Commits
.github		.github
setup-dart		setup-dart
setup-flutter		setup-flutter
setup-go		setup-go
setup-node		setup-node
setup-php		setup-php
CONTRIBUTING.md		CONTRIBUTING.md
README.md		README.md

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Back-to-code Actions

Why custom actions?

Caching philosophy — download cache, not artifacts

Available actions

setup-node

setup-php

setup-go

setup-dart

setup-flutter

Writing optimized workflows

Rule 1: Always use runs-on: self-hosted

Rule 2: Set concurrency groups

Rule 3: Set timeout-minutes on every job

Rule 4: Use path filtering to skip irrelevant jobs

Rule 5: Gate job for required checks

Rule 6: Service containers work in dind mode

Rule 7: Sparse checkout for monorepos

Rule 8: Minimize permissions

Rule 9: SHA-pin third-party actions

Complete workflow template

Go project template

Dart project template

Flutter project template

Common mistakes

Cache architecture

About

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Contributing

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Forks

Releases

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Contributors

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Rule 1: Always use `runs-on: self-hosted`

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