GitHub Actions Gradle build cache

WIP

A gradle remote build cache backed by GitHub action's cache.

Built based on @actions/cache version 1.0.7, if the version has changed significantly since then this may not work.

Built using gradle 7.0.2, using it with earlier versions may not work.

You may run into rate limiting (actions/toolkit#738), but I have not seen that in practice.

Use

Comes in two parts: the cache implementation itself, and a GitHub Action to set it up. The cache implementation is com.github.rnett.github-actions-gradle-cach:cache. You could install it manually, but it requires a baseUrl and token, and the only way to get those is from the environment of a GitHub Action (note that they are not propagated to run's environment).

To get around this, use the github action in this repo. You can include it as rnett/github-actions-gradle-cache@$version. It has three parameters, all optional:

• version - the version of the cache implementation to use. By default is the same as the action.
• is-push - whether to push to the remote build cache. True by default.
• use-build-cache - whether to add org.gradle.caching=true to ~/.gradle/gradle.properties. True by default.

It works by creating an init script (~/.gradle/init.d/gh_actions_cache.init.gradle.kts) that adds a dependency on cache and configures it. If enable is also true, it adds org.gradle.caching=true to ~/.gradle/gradle.properties to ensure the build cache is used.

Full cache

The action also has the ability to wrap actions/cache (well, not exactly, but it is very close) with reasonable defaults for gradle, controlled by 4 more parameters (also all optional):

• full-cache - whether to do this directory caching in addition to using the build cache. True by default.
• cache-key - the key to use for the cache. By default, will be calculated as described below.
• cache-key-prefix - a prefix for the key, if specified. Will be added to the default key as well.
• cache-key-postfix - a prefix for the key, if specified. Will be added to the default key as well. Will be dropped from restore keys.
• restore-keys - restore keys to use if cache-key is specified.
• cache-paths - More paths to cache (normal globs, not relative to ~/.gradle or anywhere else).

It comes with defaults set for Gradle, so by default it cashes these directories in ~/.gradle:

• nodejs
• wrapper
• yarn
• jdks
• children of caches expect for build-cache*, to avoid duplicating.

It also caches ~/konan, for Kotlin/Native support.

Like actions/cache, it also has an output cache-hit.

Files (including parts of the defaults) can be ignored by passing them to cache-paths starting with a !, the same actions/cache.

If cache-key is not specified, it uses $prefix-gradle-auto-cache-$currentOS-$workflow-$jobId-$postfix-$hash, where $hash is a hash of **/*.gradle*, **/buildSrc/src/**, **/*gradle.lockfile, **/gradle-wrapper.properties, and **/gradle.properties using hashFiles. Restore keys omitting the hash, jobId, workflow, and postfix will be used. Neither $prefix or $postfix will be included if not specified.

Note that the cache upload task will also stop any gradle daemons and delete .lock and gc.properties, as recommend here.