Slow Docker image pulls can cripple CI/CD pipeline performance, especially in parallel runner setups. This case study dives into the root causes of such slowdowns, including network congestion, cache misses, and registry throttling. The author shares practical debugging techniques using tools like `docker pull` timing analysis and runner logs. Key optimizations include using a local registry mirror, optimizing image layers, and adjusting runner concurrency settings. For teams using GitLab Runner at scale, these insights can significantly reduce pipeline wait times and improve developer productivity. The article also discusses trade-offs between image size and build speed, offering a balanced approach to CI/CD performance tuning.
A real-world case study on identifying and resolving slow Docker image pulls in parallel GitLab Runner pipelines.