Speed Up Your CI Pipelines by 8X with Docker Layer Caching
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Multi-stage Dockerfiles optimize build processes by breaking builds into stages, allowing selective copying of necessary files, which improves build speed, image security, and overall Dockerfile organization. Docker Layer Caching (DLC) significantly speeds up CI pipelines by reusing unchanged image layers, reducing build times and infrastructure costs. In the benchmarked example, Harness CI achieved an 8X improvement in build performance compared to GitHub Actions.
In modern software development, speed and efficiency are paramount. Long build times can slow down releases and hinder productivity. Docker layer caching is a powerful technique that helps optimize builds by reusing previously created image layers, reducing redundant processing. In this blog, we'll explore how Harness CI features Docker Layer Caching (DLC) to enhance build performance and streamline your CI/CD pipelines.
DLC and Multi-stage Builds
Every instruction in a Dockerfile creates a layer in the final image. Docker caches these layers to avoid rebuilding them unnecessarily, which can save significant time and reduce infrastructure costs. However, when a layer changes (e.g., modifying a file copied with COPY), Docker invalidates the cache for that layer and all subsequent layers, requiring them to be rebuilt. Understanding and optimizing layer usage helps in writing more efficient Dockerfiles, achieving faster build times, and lowering compute costs.
A multi-stage Dockerfile allows you to use multiple FROM statements to break the build process into stages. This helps keep the final image lightweight by copying only the necessary files from one stage to another, discarding anything unnecessary. It speeds up builds by leveraging layer caching, reducing the need to re-run expensive steps. Plus, it enhances security by minimizing the final image's attack surface and keeps the Dockerfile organized by separating concerns.
Harness CI Intelligence: Docker Layer Caching
Harness CI Intelligence optimizes Docker builds by leveraging Docker Layer Caching (DLC) to reuse unchanged image layers, significantly reducing build times and resource costs. When enabled, DLC restores previously built layers, avoiding redundant processing and speeding up the build and push process. Harness CI supports DLC across both Harness Cloud and self-managed infrastructure, providing flexibility in managing cache storage. This intelligent caching mechanism enhances CI/CD efficiency by minimizing infrastructure usage and improving developer productivity.
Benchmarking Build and Push to Docker
Check out the following video for a demo on running a build and push to Docker step for a Go repository using GitHub Actions and Harness CI, with Harness CI achieving an 8X improvement in build times.
The following chart summarizes the performance comparison of this benchmark (Harness CI with DLC vs. GitHub Actions):
Conclusion
Implementing Docker Layer Caching in your CI/CD pipelines can lead to significant improvements in build performance, cost savings, and overall development efficiency. By reusing unchanged layers and minimizing redundant processing, Harness CI helps teams accelerate their workflows while optimizing infrastructure usage. Whether you're running builds in Harness Cloud or a self-managed environment, enabling DLC ensures faster feedback loops and a smoother development experience. Start leveraging Docker Layer Caching today to speed up your CI pipelines and focus on delivering value faster.