See ["Caching dependencies to speed up workflows"](https://help.github.com/github/automating-your-workflow-with-github-actions/caching-dependencies-to-speed-up-workflows).
Create a workflow `.yml` file in your repositories `.github/workflows` directory. An [example workflow](#example-workflow) is available below. For more information, reference the GitHub Help Documentation for [Creating a workflow file](https://help.github.com/en/articles/configuring-a-workflow#creating-a-workflow-file).
*`path` - A list of files, directories, and wildcard patterns to cache and restore. See [`@actions/glob`](https://github.com/actions/toolkit/tree/main/packages/glob) for supported patterns.
See [Matching a cache key](https://help.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows#matching-a-cache-key) for more info.
> Note: You must use the `cache` action in your workflow before you need to use the files that might be restored from the cache. If the provided `key` doesn't match an existing cache, a new cache is automatically created if the job completes successfully.
A cache key can include any of the contexts, functions, literals, and operators supported by GitHub Actions.
For example, using the [`hashFiles`](https://help.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#hashfiles) function allows you to create a new cache when dependencies change.
See [Using contexts to create cache keys](https://help.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows#using-contexts-to-create-cache-keys)
A repository can have up to 10GB of caches. Once the 10GB limit is reached, older caches will be evicted based on when the cache was last accessed. Caches that are not accessed within the last week will also be evicted.
Cache version is unique for a combination of compression tool used for compression of cache (Gzip, Zstd, etc based on runner OS) and the path of directories being cached. If two caches have different versions, they are identified as unique cache entries. This also means that a cache created on `windows-latest` runner can't be restored on `ubuntu-latest` as cache `Version`s are different.
Example: Below example will create 3 unique caches with same keys. Ubuntu and windows runners will use different compression technique and hence create two different caches. And `build-linux` will create two different caches as the `paths` are different.
Following are some of the known practices/workarounds which community has used to fulfill specific requirements. You may choose to use them if suits your use case. Note these are not necessarily the only or the recommended solution.
A cache today is immutable and cannot be updated. But some use cases require the cache to be saved even though there was a "hit" during restore. To do so, use a `key` which is unique for every run and use `restore-keys` to restore the nearest cache. For example:
Reusing cache across feature branches is not allowed today to provide cache [isolation](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache). However if both feature branches are from same base branch, a good way to achieve this is to ensure that the base branch has a cache. This cache will then be consumable by both feature branches.
We would love for you to contribute to `actions/cache`, pull requests are welcome! Please see the [CONTRIBUTING.md](CONTRIBUTING.md) for more information.
