cache

This action allows caching dependencies and build outputs to improve workflow execution time.

Documentation

See "Caching dependencies to speed up workflows".

What's New

v3

• Added support for caching from GHES 3.5.
• Fixed download issue for files > 2GB during restore.
• Updated the minimum runner version support from node 12 -> node 16.
• Fixed avoiding empty cache save when no files are available for caching.
• Fixed tar creation error while trying to create tar with path as ~/ home folder on ubuntu-latest.
• Fixed zstd failing on amazon linux 2.0 runners.
• Fixed cache not working with github workspace directory or current directory.
• Fixed the download stuck problem by introducing a timeout of 1 hour for cache downloads.
• Fix zstd not working for windows on gnu tar in issues.
• Allowing users to provide a custom timeout as input for aborting download of a cache segment using an environment variable SEGMENT_DOWNLOAD_TIMEOUT_MIN. Default is 60 minutes.

Refer here for previous versions

Usage

Pre-requisites

Create a workflow .yml file in your repositories .github/workflows directory. An example workflow is available below. For more information, reference the GitHub Help Documentation for Creating a workflow file.

If you are using this inside a container, a POSIX-compliant tar needs to be included and accessible in the execution path.

Inputs

• path - A list of files, directories, and wildcard patterns to cache and restore. See @actions/glob for supported patterns.
• key - An explicit key for restoring and saving the cache
• restore-keys - An ordered list of keys to use for restoring stale cache if no cache hit occurred for key. Note cache-hit returns false in this case.

Environment Variables

• SEGMENT_DOWNLOAD_TIMEOUT_MIN - Segment download timeout (in minutes, default 60) to abort download of the segment if not completed in the defined number of minutes. Read more

Outputs

• cache-hit - A boolean value to indicate an exact match was found for the key

See Skipping steps based on cache-hit for info on using this output

Cache scopes

The cache is scoped to the key and branch. The default branch cache is available to other branches.

See Matching a cache key for more info.

Example workflow

name: Caching Primes

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v3

    - name: Cache Primes
      id: cache-primes
      uses: actions/cache@v3
      with:
        path: prime-numbers
        key: ${{ runner.os }}-primes

    - name: Generate Prime Numbers
      if: steps.cache-primes.outputs.cache-hit != 'true'
      run: /generate-primes.sh -d prime-numbers

    - name: Use Prime Numbers
      run: /primes.sh -d prime-numbers

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.

Implementation Examples

Every programming language and framework has its own way of caching.

See Examples for a list of actions/cache implementations for use with:

• C# - NuGet
• Clojure - Lein Deps
• D - DUB
• Deno
• Elixir - Mix
• Go - Modules
• Haskell - Cabal
• Haskell - Stack
• Java - Gradle
• Java - Maven
• Node - npm
• Node - Lerna
• Node - Yarn
• OCaml/Reason - esy
• PHP - Composer
• Python - pip
• Python - pipenv
• R - renv
• Ruby - Bundler
• Rust - Cargo
• Scala - SBT
• Swift, Objective-C - Carthage
• Swift, Objective-C - CocoaPods
• Swift - Swift Package Manager

Creating a cache key

A cache key can include any of the contexts, functions, literals, and operators supported by GitHub Actions.

For example, using the hashFiles function allows you to create a new cache when dependencies change.

  - uses: actions/cache@v3
    with:
      path: |
        path/to/dependencies
        some/other/dependencies        
      key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}

Additionally, you can use arbitrary command output in a cache key, such as a date or software version:

  # http://man7.org/linux/man-pages/man1/date.1.html
  - name: Get Date
    id: get-date
    run: |
      echo "::set-output name=date::$(/bin/date -u "+%Y%m%d")"      
    shell: bash

  - uses: actions/cache@v3
    with:
      path: path/to/dependencies
      key: ${{ runner.os }}-${{ steps.get-date.outputs.date }}-${{ hashFiles('**/lockfiles') }}

See Using contexts to create cache keys

Cache Limits

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.

Skipping steps based on cache-hit

Using the cache-hit output, subsequent steps (such as install or build) can be skipped when a cache hit occurs on the key.

Example:

steps:
  - uses: actions/checkout@v3

  - uses: actions/cache@v3
    id: cache
    with:
      path: path/to/dependencies
      key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}

  - name: Install Dependencies
    if: steps.cache.outputs.cache-hit != 'true'
    run: /install.sh

Note: The id defined in actions/cache must match the id in the if statement (i.e. steps.[ID].outputs.cache-hit)

Cache Version

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 Versions 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.

jobs:
  build-linux:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Cache Primes
        id: cache-primes
        uses: actions/cache@v3
        with:
          path: prime-numbers
          key: primes

      - name: Generate Prime Numbers
        if: steps.cache-primes.outputs.cache-hit != 'true'
        run: ./generate-primes.sh -d prime-numbers

      - name: Cache Numbers
        id: cache-numbers
        uses: actions/cache@v3
        with:
          path: numbers
          key: primes

      - name: Generate Numbers
        if: steps.cache-numbers.outputs.cache-hit != 'true'
        run: ./generate-primes.sh -d numbers

  build-windows:
    runs-on: windows-latest
    steps:
      - uses: actions/checkout@v3

      - name: Cache Primes
        id: cache-primes
        uses: actions/cache@v3
        with:
          path: prime-numbers
          key: primes

      - name: Generate Prime Numbers
        if: steps.cache-primes.outputs.cache-hit != 'true'
        run: ./generate-primes -d prime-numbers

Known practices and workarounds

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.

Cache segment restore timeout

A cache gets downloaded in multiple segments of fixed sizes (1GB for a 32-bit runner and 2GB for a 64-bit runner). Sometimes, a segment download gets stuck which causes the workflow job to be stuck forever and fail. Version v3.0.8 of actions/cache introduces a segment download timeout. The segment download timeout will allow the segment download to get aborted and hence allow the job to proceed with a cache miss.

Default value of this timeout is 60 minutes and can be customized by specifying an environment variable named SEGMENT_DOWNLOAD_TIMEOUT_MINS with timeout value in minutes.

Update a cache

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:

    - name: update cache on every commit
      uses: actions/cache@v3
      with:
        path: prime-numbers
        key: primes-${{ runner.os }}-${{ github.run_id }} # Can use time based key as well
        restore-keys: |
          primes-${{ runner.os }}          

Please note that this will create a new cache on every run and hence will consume the cache quota.

Use cache across feature branches

Reusing cache across feature branches is not allowed today to provide cache isolation. However if both feature branches are from the default branch, a good way to achieve this is to ensure that the default branch has a cache. This cache will then be consumable by both feature branches.

Improving cache restore performance on Windows/Using cross-os caching

Currently, cache restore is slow on Windows due to tar being inherently slow and the compression algorithm gzip in use. zstd is the default algorithm in use on linux and macos. It was disabled on Windows due to issues with bsd tar(libarchive), the tar implementation in use on Windows.

To improve cache restore performance, we can re-enable zstd as the compression algorithm using the following workaround. Add the following step to your workflow before the cache step:

    - if: ${{ runner.os == 'Windows' }}
      name: Use GNU tar
      shell: cmd
      run: |
        echo "Adding GNU tar to PATH"
        echo C:\Program Files\Git\usr\bin>>"%GITHUB_PATH%"        

The cache action will use GNU tar instead of bsd tar on Windows. This should work on all Github Hosted runners as it is. For self-hosted runners, please ensure you have GNU tar and zstd installed.

The above workaround is also needed if you wish to use cross-os caching since difference of compression algorithms will result in different cache versions for the same cache key. So the above workaround will ensure zstd is used for caching on all platforms thus resulting in the same cache version for the same cache key.

Contributing

We would love for you to contribute to actions/cache, pull requests are welcome! Please see the CONTRIBUTING.md for more information.

License

The scripts and documentation in this project are released under the MIT License