What are GitLab’s cached dependencies?

Can anyone please tell me what are GitLab’s cached dependencies.

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Every CI/CD job requires some kind of building phase where the est target is built using 3rd party dependencies. Depending on the stack, these dependencies are fetches using plugin managers, module importers, etc. The common pain point in building with 3rd party modules across all the languages is that it takes a lot of time to fetch dependencies from 3rd party sources and compile them. Imagine doing this process over a hundred times a day for multiple projects and calculate the time and resource wastage it incurs. Not a pleasant picture, right?

If there was a way to cache these built dependencies and use these cached dependencies for multiple pipelines, it would make CI build much faster and reduce bandwidth wastage and will unclog the CI pipelines so that same Infra can be used for much more builds.GitLab’s Cached Dependencies allow you to exactly do this straight out of .gitlab-ci.yaml file.

It’s as simple as setting a cache dictionary in yaml file and key attribute. Just ensure you use the same key in all the jobs where cached directory is required. Common practice to ensure cache between branches is to use git bases environment variables as cache key. For example, CI_COMMIT_BRANCH can help you utilize cache whenever a job is run for a branch.

Gitlab CI/CD provides powerful primitives to invalidate cache. This can be done either via UI or by clearing the cache key.

An extension: You can optionally fetch dependencies and build them only package manifest file changes. This is superior to using cache always. For example, only fetching node js dependencies whenever package.json changes.

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