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actions / cache

Cache dependencies and build outputs in GitHub Actions
MIT License
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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:

Tests

Documentation

See "Caching dependencies to speed up workflows".

What's New

v4

v3

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

Environment Variables

Outputs

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:

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. ```yaml 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.

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