GitHub Actions - Shared Workflows

Docker - Build image

Workflow: .github/workflows/docker-image-build.yml

This workflow builds Docker images with optimized caching for faster builds. It supports multi-architecture builds for both linux/amd64 and linux/arm64 platforms using the "image" exporter type which properly handles manifest lists required for multi-architecture images.

Inputs

• image: name of the docker image, e.g. ghcr.io/requirecloud/some-image
• registry: Docker Registry where to push the image. Default value: ghcr.io
• push: Should the image actually be pushed to Registry. Default value: true

Caching

The workflow uses two types of caching to speed up builds:

1. GitHub Actions Cache: Always enabled, persists between workflow runs

   • Repository-wide cache: Shared across all branches
   • Branch-specific cache: Optimized for the current branch

2. Registry Cache: Enabled when push is set to true, stores cache in the registry with a buildcache tag

These caching mechanisms significantly reduce build times by reusing layers from previous builds.

Optimizing for Cache Effectiveness

For best caching results:

1. Structure your Dockerfile efficiently:

   • Place infrequently changing layers (e.g., base image, dependencies) at the beginning
   • Place frequently changing layers (e.g., application code) at the end

2. Use .dockerignore file to exclude unnecessary files from the build context

3. Ensure consistent build environments across different workflows that use the same image

4. Be patient with initial builds - caching benefits become apparent after the first few builds

Usage

name: Build my Docker image

on:
  push:
  workflow_dispatch:

jobs:

  docker-image-build:

    uses: requirecloud/gha-workflows/.github/workflows/docker-image-build.yml@main
    with:
      image: ghcr.io/requirecloud/some-image
    secrets: inherit