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](./restore/README.md)
>* [Save action](./save/README.md)

[![Tests](https://github.com/actions/cache/actions/workflows/workflow.yml/badge.svg)](https://github.com/actions/cache/actions/workflows/workflow.yml)

## Documentation

See ["Caching dependencies to speed up workflows"](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows).

## What's New

### 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](restore/action.yml) and [save](save/action.yml).
* Support cross-os caching as an opt-in feature. See [Cross OS caching](./tips-and-workarounds.md#cross-os-cache) for more info.
* Added option to fail job on cache miss. See [Exit workflow on cache miss](./restore/README.md#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](https://github.com/actions/cache/blob/v2/README.md) for older updates.

## Usage

### Pre-requisites

Create a workflow `.yml` file in your repository's `.github/workflows` directory. An [example workflow](#example-cache-workflow) is available below. For more information, see the GitHub Help Documentation for [Creating a workflow file](https://help.github.com/en/articles/configuring-a-workflow#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](https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cross-os-cache) 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](#creating-a-cache-key).
* `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.
* `restore-keys` - An ordered list of prefix-matched keys to use 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](https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout)

### Outputs

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

    > **Note** `cache-hit` will only be set to `true` when a cache hit occurs for the exact `key` match. For a partial key match via `restore-keys` or a cache miss, it will be set to `false`.

See [Skipping steps based on cache-hit](#skipping-steps-based-on-cache-hit) for info on using this output

### Cache scopes

The cache is scoped to the key, [version](#cache-version), and branch. The default branch cache is available to other branches.

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.

### Example cache workflow

#### Restoring and saving cache using a single action

```yaml
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
```

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

```yaml
name: Caching Primes

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v3

    - name: Restore cached Primes
      id: cache-primes-restore
      uses: actions/cache/restore@v3
      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@v3
      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](./caching-strategies.md) 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](examples.md) for a list of `actions/cache` implementations for use with:

* [C# - NuGet](./examples.md#c---nuget)
* [Clojure - Lein Deps](./examples.md#clojure---lein-deps)
* [D - DUB](./examples.md#d---dub)
* [Deno](./examples.md#deno)
* [Elixir - Mix](./examples.md#elixir---mix)
* [Go - Modules](./examples.md#go---modules)
* [Haskell - Cabal](./examples.md#haskell---cabal)
* [Haskell - Stack](./examples.md#haskell---stack)
* [Java - Gradle](./examples.md#java---gradle)
* [Java - Maven](./examples.md#java---maven)
* [Node - npm](./examples.md#node---npm)
* [Node - Lerna](./examples.md#node---lerna)
* [Node - Yarn](./examples.md#node---yarn)
* [OCaml/Reason - esy](./examples.md#ocamlreason---esy)
* [PHP - Composer](./examples.md#php---composer)
* [Python - pip](./examples.md#python---pip)
* [Python - pipenv](./examples.md#python---pipenv)
* [R - renv](./examples.md#r---renv)
* [Ruby - Bundler](./examples.md#ruby---bundler)
* [Rust - Cargo](./examples.md#rust---cargo)
* [Scala - SBT](./examples.md#scala---sbt)
* [Swift, Objective-C - Carthage](./examples.md#swift-objective-c---carthage)
* [Swift, Objective-C - CocoaPods](./examples.md#swift-objective-c---cocoapods)
* [Swift - Swift Package Manager](./examples.md#swift---swift-package-manager)
* [Swift - Mint](./examples.md#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`](https://docs.github.com/en/actions/learn-github-actions/expressions#hashfiles) function allows you to create a new cache when dependencies change.

```yaml
  - 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:

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

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)

## 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:

```yaml
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 a hash [generated](https://github.com/actions/toolkit/blob/500d0b42fee2552ae9eeb5933091fe2fbf14e72d/packages/cache/src/internal/cacheHttpClient.ts#L73-L90) 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 `Version`s are different.

> Pro tip: The [list caches](https://docs.github.com/en/rest/actions/cache#list-github-actions-caches-for-a-repository) API can be used to get the version of a cache. This can be helpful to troubleshoot cache miss due to version.

<details>
  <summary>Example</summary>
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@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
```

</details>

## 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](./tips-and-workarounds.md#cache-segment-restore-timeout)
* [Update a cache](./tips-and-workarounds.md#update-a-cache)
* [Use cache across feature branches](./tips-and-workarounds.md#use-cache-across-feature-branches)
* [Cross OS cache](./tips-and-workarounds.md#cross-os-cache)
* [Force deletion of caches overriding default cache eviction policy](./tips-and-workarounds.md#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](https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables) page.

## Main functionalities

The `cache` action in this repository provides several main functionalities:

* **Caching dependencies and build outputs**: The primary function of the `cache` action is to cache dependencies and build outputs to improve workflow execution time. This is specified in the `description` field of the `action.yml` file (`action.yml`). 🗃️
* **Restoring cache**: The `cache` action can restore cached files, directories, and wildcard patterns specified in the `path` input. This is done using the `restoreCache` function from the `@actions/cache` package (`src/restoreImpl.ts`). 🔄
* **Saving cache**: The `cache` action can save files, directories, and wildcard patterns specified in the `path` input to the cache. This is done using the `saveCache` function from the `@actions/cache` package (`src/saveImpl.ts`). 💾
* **Cross-OS caching**: The `cache` action supports cross-OS caching, allowing Windows runners to save or restore caches that can be restored or saved respectively on other platforms. This is controlled by the `enableCrossOsArchive` input (`action.yml`). 🌐
* **Failing on cache miss**: The `cache` action can be configured to fail the workflow if a cache entry is not found. This is controlled by the `fail-on-cache-miss` input (`action.yml`). ❌
* **Lookup-only mode**: The `cache` action can check if a cache entry exists for the given inputs without downloading the cache. This is controlled by the `lookup-only` input (`action.yml`). 🔍

## Contributing

We would love for you to contribute to `actions/cache`. Pull requests are welcome! Please see the [CONTRIBUTING.md](CONTRIBUTING.md) for more information.

## License

The scripts and documentation in this project are released under the [MIT License](LICENSE)