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Dewan Ahmed for Harness

Posted on • Originally published at harness.io

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Speed Up Your CI Pipelines with Docker Layer Caching

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.

Harness CI Intelligence Overview

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.
Speed Up Your CI Pipelines with Docker Layer Caching

The following chart summarizes the performance comparison of this benchmark (Harness CI with DLC vs. GitHub Actions):

Benchmark: Harness CI 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.

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