cache/README.md

Cache action

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

Two other actions are available in addition to the primary cache action:

• Restore action
• Save action

Documentation

See "Caching dependencies to speed up workflows".

What's New

⚠️ Important changes

The cache backend service has been rewritten from the ground up for improved performance and reliability. actions/cache now integrates with the new cache service (v2) APIs.

The new service will gradually roll out as of February 1st, 2025. The legacy service will also be sunset on the same date. Changes in these release are fully backward compatible.

We are deprecating some versions of this action. We recommend upgrading to version v4 or v3 as soon as possible before February 1st, 2025. (Upgrade instructions below).

If you are using pinned SHAs, please use the SHAs of versions v4.2.0 or v3.4.0

If you do not upgrade, all workflow runs using any of the deprecated actions/cache will fail.

Upgrading to the recommended versions will not break your workflows.

Read more about the change & access the migration guide: reference to the announcement.

v4

• Updated to node 20

v3

• Added support for caching in 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_MINS. Default is 10 minutes.
• New actions are available for granular control over caches - restore and save.
• Support cross-os caching as an opt-in feature. See Cross OS caching for more info.
• Added option to fail job on cache miss. See Exit workflow on cache miss for more info.
• Fix zstd not being used after zstd version upgrade to 1.5.4 on hosted runners
• Added option to lookup cache without downloading it.
• Reduced segment size to 128MB and segment timeout to 10 minutes to fail fast in case the cache download is stuck.

See the v2 README.md for older updates.

Usage

Pre-requisites

Create a workflow .yml file in your repository's .github/workflows directory. An example workflow is available below. For more information, see 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 from the execution path.

If you are using a self-hosted Windows runner, GNU tar and zstd are required for Cross-OS caching to work. They are also recommended to be installed in general so the performance is on par with hosted Windows runners.

Inputs

• key - An explicit key for a cache entry. See creating a cache key.
• path - A list of files, directories, and wildcard patterns to cache and restore. See @actions/glob for supported patterns.
• restore-keys - An ordered multiline string listing the prefix-matched keys, that are used for restoring stale cache if no cache hit occurred for key.
• enableCrossOsArchive - An optional boolean when enabled, allows Windows runners to save or restore caches that can be restored or saved respectively on other platforms. Default: false
• fail-on-cache-miss - Fail the workflow if cache entry is not found. Default: false
• lookup-only - If true, only checks if cache entry exists and skips download. Does not change save cache behavior. Default: false

Environment Variables

• SEGMENT_DOWNLOAD_TIMEOUT_MINS - Segment download timeout (in minutes, default 10) to abort download of the segment if not completed in the defined number of minutes. Read more

Outputs

• cache-hit - A string value to indicate an exact match was found for the key.
  • If there's a cache hit, this will be 'true' or 'false' to indicate if there's an exact match for key.
  • If there's a cache miss, this will be an empty string.

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

Cache scopes

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

See Matching a cache key for more info.

Example cache workflow

Restoring and saving cache using a single action

name: Caching Primes

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4

    - name: Cache Primes
      id: cache-primes
      uses: actions/cache@v4
      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

The cache action provides a cache-hit output which is set to true when the cache is restored using the primary key and false when the cache is restored using restore-keys or no cache is restored.

Using a combination of restore and save actions

name: Caching Primes

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4

    - name: Restore cached Primes
      id: cache-primes-restore
      uses: actions/cache/restore@v4
      with:
        path: |
          path/to/dependencies
          some/other/dependencies          
        key: ${{ runner.os }}-primes
    .
    . //intermediate workflow steps
    .
    - name: Save Primes
      id: cache-primes-save
      uses: actions/cache/save@v4
      with:
        path: |
          path/to/dependencies
          some/other/dependencies          
        key: ${{ steps.cache-primes-restore.outputs.cache-primary-key }}

Note

You must use the cache or restore action in your workflow before you need to use the files that might be restored from the cache. If the provided key matches an existing cache, a new cache is not created and if the provided key doesn't match an existing cache, a new cache is automatically created provided the job completes successfully.

Caching Strategies

With the introduction of the restore and save actions, a lot of caching use cases can now be achieved. Please see the caching strategies document for understanding how you can use the actions strategically to achieve the desired goal.

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:

• Bun
• 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
• Swift - Mint

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@v4
    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 "date=$(/bin/date -u "+%Y%m%d")" >> $GITHUB_OUTPUT      
    shell: bash

  - uses: actions/cache@v4
    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. It is recommended to install missing/updated dependencies in case of a partial key match when the key is dependent on the hash of the package file.

Example:

steps:
  - uses: actions/checkout@v4

  - uses: actions/cache@v4
    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 a hash generated for a combination of compression tool used (Gzip, Zstd, etc. based on the runner OS) and the path of directories being cached. If two caches have different versions, they are identified as unique caches while matching. This, for example, means that a cache created on a windows-latest runner can't be restored on ubuntu-latest as cache Versions are different.

Pro tip: The list caches API can be used to get the version of a cache. This can be helpful to troubleshoot cache miss due to version.

Example

The workflow 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@v4

      - name: Cache Primes
        id: cache-primes
        uses: actions/cache@v4
        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@v4
        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@v4

      - name: Cache Primes
        id: cache-primes
        uses: actions/cache@v4
        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

There are a number of community practices/workarounds to fulfill specific requirements. You may choose to use them if they suit your use case. Note these are not necessarily the only solution or even a recommended solution.

• Cache segment restore timeout
• Update a cache
• Use cache across feature branches
• Cross OS cache
• Force deletion of caches overriding default cache eviction policy

Windows environment variables

Please note that Windows environment variables (like %LocalAppData%) will NOT be expanded by this action. Instead, prefer using ~ in your paths which will expand to the HOME directory. For example, instead of %LocalAppData%, use ~\AppData\Local. For a list of supported default environment variables, see the Learn GitHub Actions: Variables page.

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