GitHub Actions cache

Experimental

This is an experimental feature. The interface and behavior are unstable and may change in future releases.

The GitHub Actions cache utilizes the GitHub-provided Action's cache or other cache services supporting the GitHub Actions cache protocol. This is the recommended cache to use inside your GitHub Actions workflows, as long as your use case falls within the size and usage limits set by GitHub.

This cache storage backend is not supported with the default docker driver. To use this feature, create a new builder using a different driver. See Build drivers for more information.

Synopsis

$ docker buildx build --push -t <registry>/<image> \
  --cache-to type=gha[,parameters...] \
  --cache-from type=gha[,parameters...] .

The following table describes the available CSV parameters that you can pass to --cache-to and --cache-from.

NameOptionTypeDefaultDescription
urlcache-to,cache-fromString$ACTIONS_CACHE_URLCache server URL, see authentication.
tokencache-to,cache-fromString$ACTIONS_RUNTIME_TOKENAccess token, see authentication.
scopecache-to,cache-fromStringbuildkitWhich scope cache object belongs to, see scope
modecache-tomin,maxminCache layers to export, see cache mode.
ignore-errorcache-toBooleanfalseIgnore errors caused by failed cache exports.
timeoutcache-to,cache-fromString10mMax duration for importing or exporting cache before it's timed out.
repositorycache-toStringGitHub repository used for cache storage.
ghtokencache-toStringGitHub token required for accessing the GitHub API.

Authentication

If the url or token parameters are left unspecified, the gha cache backend will fall back to using environment variables. If you invoke the docker buildx command manually from an inline step, then the variables must be manually exposed. Consider using the crazy-max/ghaction-github-runtime, GitHub Action as a helper for exposing the variables.

Scope

Scope is a key used to identify the cache object. By default, it is set to buildkit. If you build multiple images, each build will overwrite the cache of the previous, leaving only the final cache.

To preserve the cache for multiple builds, you can specify this scope attribute with a specific name. In the following example, the cache is set to the image name, to ensure each image gets its own cache:

$ docker buildx build --push -t <registry>/<image> \
  --cache-to type=gha,url=...,token=...,scope=image \
  --cache-from type=gha,url=...,token=...,scope=image .
$ docker buildx build --push -t <registry>/<image2> \
  --cache-to type=gha,url=...,token=...,scope=image2 \
  --cache-from type=gha,url=...,token=...,scope=image2 .

GitHub's cache access restrictions, still apply. Only the cache for the current branch, the base branch and the default branch is accessible by a workflow.

Using docker/build-push-action

When using the docker/build-push-action, the url and token parameters are automatically populated. No need to manually specify them, or include any additional workarounds.

For example:

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    context: .
    push: true
    tags: "<registry>/<image>:latest"
    cache-from: type=gha
    cache-to: type=gha,mode=max

Avoid GitHub Actions cache API throttling

GitHub's usage limits and eviction policy causes stale cache entries to be removed after a certain period of time. By default, the gha cache backend uses the GitHub Actions cache API to check the status of cache entries.

The GitHub Actions cache API is subject to rate limiting if you make too many requests in a short period of time, which may happen as a result of cache lookups during a build using the gha cache backend.

#31 exporting to GitHub Actions Cache
#31 preparing build cache for export
#31 preparing build cache for export 600.3s done
#31 ERROR: maximum timeout reached
------
 > exporting to GitHub Actions Cache:
------
ERROR: failed to solve: maximum timeout reached
make: *** [Makefile:35: release] Error 1
Error: Process completed with exit code 2.

To mitigate this issue, you can supply a GitHub token to BuildKit. This lets BuildKit utilize the standard GitHub API for checking cache keys, thereby reducing the number of requests made to the cache API.

To provide a GitHub token, you can use the ghtoken parameter, and a repository parameter to specify the repository to use for cache storage. The ghtoken parameter is a GitHub token with the repo scope, which is required to access the GitHub Actions cache API.

The ghtoken parameter is automatically set to the value of secrets.GITHUB_TOKEN when you build with the docker/build-push-action action. You can also set the ghtoken parameter manually using the github-token input, as shown in the following example:

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    context: .
    push: true
    tags: "<registry>/<image>:latest"
    cache-from: type=gha
    cache-to: type=gha,mode=max
    github-token: ${{ secrets.MY_CUSTOM_TOKEN }}

Further reading

For an introduction to caching see Docker build cache.

For more information on the gha cache backend, see the BuildKit README.

For more information about using GitHub Actions with Docker, see Introduction to GitHub Actions