Introduction to CI/CD Pipeline Docker Builds

In the world of continuous integration and continuous deployment (CI/CD), building Docker images efficiently is pivotal. The key challenge often encountered is the absence of cache in CI/CD pipelines, unlike the local environment where resources and dependencies are readily available. This article aims to address this challenge by outlining strategies to optimize Docker builds in any CI/CD platform, enhancing build times and efficiency.

The Universal Approach: Cache Creation and Utilization

Cache Mechanisms Explained

Two primary methods exist for integrating cache into the CI/CD pipeline:

1. Directing the Builder to a Cached Repository: Docker or other building tools can fetch image layers from a repository, using them as a cache.

2. Storing Layers in a Filesystem Accessible to the Pipeline: Here, the cache is created by pushing the image to a repository or filesystem, which is then utilized in subsequent builds.

Docker with BuildKit: A Simple Yet Effective Solution

Utilizing BuildKit for Enhanced Performance

Docker’s integration with BuildKit, a set of enhancements for docker build, offers improved performance and caching functionality. The process involves enabling BuildKit by setting DOCKER_BUILDKIT=1 and utilizing the BUILDKIT_INLINE_CACHE=1 build argument. This approach ensures that metadata needed for caching is written into the image, which is later used to determine cacheable layers.

Steps for Utilizing Docker with BuildKit

1. Warm-Up Cache:

    DOCKER_BUILDKIT=1 docker build -t example/docker-cached --build-arg BUILDKIT_INLINE_CACHE=1 .
   

2. Push the Image:

    docker push example/docker-cached
   

3. Build Using Cache Repository:

    DOCKER_BUILDKIT=1 docker build --cache-from example/docker-cached .
   

Advanced Control with Upstream BuildKit

For those seeking greater customization, directly using the upstream BuildKit project is recommended. This involves downloading binaries, placing them in the system path, and starting the BuildKit daemon. A more intricate command line is required for this approach, providing flexibility and control over the build and caching process.

Integrating with Kubernetes

To leverage these caching strategies in Kubernetes, additional configurations are required. This involves setting up credentials for pushing the image and configuring volumes for the workspace. A Kubernetes Job can be crafted to create a Dockerfile in the workspace, followed by executing the build process using either Docker with BuildKit.

Conclusion: Optimizing Docker Builds in CI/CD

Efficient Docker builds in CI/CD pipelines are achievable through strategic caching. Whether using Docker with BuildKit, upstream BuildKit, or Docker-less tools like Kaniko, each method offers unique advantages. By understanding and implementing these techniques, teams can significantly reduce build times and improve pipeline efficiency.