> See the [setup-gradle documentation](https://github.com/gradle/actions/tree/main/setup-gradle) for up-to-date documentation for `gradle/actions/setup-gradle`.
- Easily [configure your workflow to use a specific version of Gradle](#choose-a-specific-gradle-version) using the `gradle-version` parameter. Gradle distributions are automatically downloaded and cached.
- More sophisticated and more efficient caching of Gradle User Home between invocations, compared to `setup-java` and most custom configurations using `actions/cache`. [More details below](#caching-build-state-between-jobs).
- Detailed reporting of cache usage and cache configuration options allow you to [optimize the use of the GitHub actions cache](#optimizing-cache-effectiveness).
The recommended way to use the `gradle-build-action` is in an initial "Setup Gradle" step, with subsequent steps invoking Gradle directly with a `run` step. This makes the action minimally invasive, and allows a workflow to configure and execute a Gradle execution in any way.
The `gradle-build-action` works by configuring environment variables and by adding a set of Gradle init-scripts to the Gradle User Home. These will apply to all Gradle executions on the runner, no matter how Gradle is invoked.
This means that if you have an existing workflow that executes Gradle with a `run` step, you can add an initial "Setup Gradle" Step to benefit from caching, build-scan capture and other features of the gradle-build-action.
The `gradle-build-action` will use the GitHub Actions cache to save and restore reusable state that may be speed up a subsequent build invocation. This includes most content that is downloaded from the internet as part of a build, as well as expensive to create content like compiled build scripts, transformed Jar files, etc.
State will be restored from the cache during the first `gradle-build-action` step for any workflow job, and cache entries will be written back to the cache at the end of the job, after all Gradle executions have completed.
In some circumstances it makes sense to change this default, and to configure a workflow Job to read existing cache entries but not to write changes back.
You can configure read-only caching for the `gradle-build-action` as follows:
When the action detects that the Gradle User Home caches directory already exists (`~/.gradle/caches`), then by default it will not overwrite the existing content of this directory.
This can occur when a prior action initializes this directory, or when using a self-hosted runner that retains this directory between uses.
In this case the Job Summary will display a message like:
> Caching for gradle-build-action was disabled due to pre-existing Gradle User Home
If you want override the default and have the `gradle-build-action` caches overwrite existing content in the Gradle User Home, you can set the `cache-overwrite-existing` parameter to 'true':
When Gradle is executed with the [configuration-cache](https://docs.gradle.org/current/userguide/configuration_cache.html) enabled, the configuration-cache data is stored
in the project directory, at `<project-dir>/.gradle/configuration-cache`. Due to the way the configuration-cache works, [this file may contain stored credentials and other
secrets](https://docs.gradle.org/release-nightly/userguide/configuration_cache.html#config_cache:secrets), and this data needs to be encrypted in order to be safely stored in the GitHub Actions cache.
In order to benefit from configuration caching in your GitHub Actions workflow, you must:
- Execute your build with Gradle 8.6 or newer. This can be achieved directly, or via the Gradle Wrapper.
- Generate a [valid Gradle encryption key](https://docs.gradle.org/8.6-rc-1/userguide/configuration_cache.html#config_cache:secrets:configuring_encryption_key) and save it as a [GitHub Actions secret](https://docs.github.com/en/actions/security-guides/using-secrets-in-github-actions).
- Avoid using `actions/cache` configured to cache the Gradle User Home, [as described in this example](https://github.com/actions/cache/blob/main/examples.md#java---gradle).
- Avoid using `actions/setup-java` with the `cache: gradle` option, [as described here](https://github.com/actions/setup-java#caching-gradle-dependencies).
Using either of these mechanisms may interfere with the caching provided by this action. If you choose to use a different mechanism to save and restore the Gradle User Home, you should disable the caching provided by this action, as described above.
The GitHub Actions cache has some properties that present problems for efficient caching of the Gradle User Home.
- Immutable entries: once a cache entry is written for a key, it cannot be overwritten or changed.
- Branch scope: cache entries written for a Git branch are not visible from actions running against different branches. Entries written for the default branch are visible to all. https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache
- Restore keys: if no exact match is found, a set of partial keys can be provided that will match by cache key prefix. https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#matching-a-cache-key
Each of these properties has influenced the design and implementation of the caching in `gradle-build-action`, as described below.
Using experiments and observations, we have attempted to identify which Gradle User Home content is worth saving and restoring between build invocations. We considered both the respective size of the content and the impact this content has on build times. As well as the obvious candidates like downloaded dependencies, we saw that compiled build scripts, transformed Jar files and other content can also have a significant impact.
In the end, we opted to save and restore as much content as is practical, including:
-`caches/<version>/generated-gradle-jars`: These files are generated on first use of a particular Gradle version, and are expensive to recreate
-`caches/<version>/kotlin-dsl` and `caches/<version>/scripts`: These are the compiled build scripts. The Kotlin ones in particular can benefit from caching.
-`caches/modules-2`: The downloaded dependencies
-`caches/transforms-3`: The results of artifact transforms
-`caches/jars-9`: Jar files that have been processed/instrumented by Gradle
-`caches/build-cache-1`: The local build cache
In certain cases a particular section of Gradle User Home will be too large to make caching effective. In these cases, particular subdirectories can be excluded from caching. See [Exclude content from Gradle User Home cache](#exclude-content-from-gradle-user-home-cache).
- The entire content of `buildSrc` or any included builds that provide plugins.
- The entire content of the repository, in the case of the local build cache.
- The actual build command that was invoked, including system properties and environment variables.
For this reason, it's very difficult to create a cache key that will deterministically map to a saved Gradle User Home state. So instead of trying to reliably hash all of these inputs to generate a cache key, the Gradle User Home cache key is based on the currently executing Job and the current commit hash for the repository.
In most cases, no exact match will exist for the cache key. Instead, the Gradle User Home will be restored for the closest matching cache entry, using a set of "restore keys". The entries will be matched with the following precedence:
Due to branch scoping of cache entries, the above match will be first performed for entries from the same branch, and then for the default ('main') branch.
After the Job is complete, the current Gradle User Home state will be collected and written as a new cache entry with the complete cache key. Old entries will be expunged from the GitHub Actions cache on a least-recently-used basis.
Note that while effective, this mechanism is not inherently efficient. It requires the entire Gradle User Home directory to be stored separately for each branch, for every OS+Job+Matrix combination. In addition, a new cache entry to be written on every GitHub Actions run.
This inefficiency is effectively mitigated by [Deduplication of Gradle User Home cache entries](#deduplication-of-gradle-user-home-cache-entries), and can be further optimized for a workflow using the techniques described in [Optimizing cache effectiveness](#optimizing-cache-effectiveness).
To reduce duplication between cache entries, certain artifacts in Gradle User Home are extracted and cached independently based on their identity. This allows each Gradle User Home cache entry to be relatively small, sharing common elements between them without duplication.
Artifacts that are cached independently include:
- Downloaded dependencies
- Downloaded wrapper distributions
- Generated Gradle API jars
- Downloaded Java Toolchains
For example, this means that all jobs executing a particular version of the Gradle wrapper will share a single common entry for this wrapper distribution and one for each of the generated Gradle API jars.
At the end of a Job, the `gradle-build-action` will write a summary of the Gradle builds executed, together with a detailed report of the cache entries that were read and written during the Job. This report can provide valuable insights that may help to determine the right way to optimize the cache usage for your workflow.
Consider a workflow that first runs a Job "compile-and-unit-test" to compile the code and run some basic unit tests, which is followed by a matrix of parallel "integration-test" jobs that each run a set of integration tests for the repository. Each "integration test" Job requires all of the dependencies required by "compile-and-unit-test", and possibly one or 2 additional dependencies.
By default, a new cache entry will be written on completion of each integration test job. If no additional dependencies were downloaded then this cache entry will share the "dependencies" entry with the "compile-and-unit-test" job, but if a single dependency was downloaded then an entire new "dependencies" entry would be written. (The `gradle-build-action` does not _yet_ support a layered cache that could do this more efficiently). If each of these "integration-test" entries with their different "dependencies" entries is too large, then it could result in other important entries being evicted from the GitHub Actions cache.
There are some techniques that can be used to avoid/mitigate this issue:
- Configure the "integration-test" jobs with `cache-read-only: true`, meaning that the Job will use the entry written by the "compile-and-unit-test" job. This will avoid the overhead of cache entries for each of these jobs, at the expense of re-downloading any additional dependencies required by "integration-test".
- Add an additional step to the "compile-and-unit-test" job which downloads all dependencies required by the integration-test jobs but does not execute the tests. This will allow the "dependencies" entry for "compile-and-unit-test" to be shared among all cache entries for "integration-test". The resulting "integration-test" entries should be much smaller, reducing the potential for eviction.
- Combine the above 2 techniques, so that no cache entry is written by "integration-test" jobs, but all required dependencies are already present from the restored "compile-and-unit-test" entry.
Workflow runs can restore caches created in either the current branch or the default branch (usually main).
This means that each branch will have it's own Gradle User Home cache scope, and will not benefit from cache entries written for other (non-default) branches.
- For `pull_request` triggered runs, the cache scope is limited to the merge ref (`refs/pull/.../merge`) and can only be restored by re-runs of the same pull request.
- For `merge_group` triggered runs, the cache scope is limited to a temporary branch with a special prefix created to validate pull request changes, and won't be available on subsequent Merge Queue executions.
and the contents to be cached can be fine tuned by including and excluding certain paths within Gradle User Home.
```yaml
# Cache downloaded JDKs in addition to the default directories.
gradle-home-cache-includes: |
caches
notifications
jdks
# Exclude the local build-cache and keyrings from the directories cached.
gradle-home-cache-excludes: |
caches/build-cache-1
caches/keyrings
```
You can specify any number of fixed paths or patterns to include or exclude.
File pattern support is documented at https://docs.github.com/en/actions/learn-github-actions/workflow-syntax-for-github-actions#patterns-to-match-file-paths.
### Use of custom init-scripts in Gradle User Home
Note that the action collects information about Gradle invocations via an [Initialization Script](https://docs.gradle.org/current/userguide/init_scripts.html#sec:using_an_init_script)
located at `USER_HOME/.gradle/init.d/gradle-build-action.build-result-capture.init.gradle`.
If you are adding any custom init scripts to the `USER_HOME/.gradle/init.d` directory, it may be necessary to ensure these files are applied prior to `gradle-build-action.build-result-capture.init.gradle`.
Since Gradle applies init scripts in alphabetical order, one way to ensure this is via file naming.
You can use the `gradle-build-action` on GitHub Enterprise Server, and benefit from the improved integration with Gradle. Depending on the version of GHES you are running, certain features may be limited:
- Support for GitHub Actions Job Summary (requires GHES 3.6+ : GitHub Actions Job Summary support was introduced in GHES 3.6). In earlier versions of GHES the build-results summary and caching report will be written to the workflow log, as part of the post-action step.
> The simplest (and recommended) way to generate a dependency graph is via a separate workflow
> using `gradle/actions/dependency-submission`. This action will attempt to detect all dependencies used by your build
> without building and testing the project itself.
>
> See the [dependency-submission documentation](https://github.com/gradle/actions/blob/main/dependency-submission/README.md) for up-to-date documentation.
The `gradle-build-action` provides support for injecting and configuring the Develocity Gradle plugin into any Gradle build, without any modification to the project sources.
This is achieved via an init-script installed into Gradle User Home, which is enabled and parameterized via environment variables.
The same auto-injection behavior is available for the Common Custom User Data Gradle plugin, which enriches any build scans published with additional useful information.
This configuration will automatically apply `v3.16.2` of the [Develocity Gradle plugin](https://docs.gradle.com/enterprise/gradle-plugin/), and publish build scans to https://develocity.your-server.com.
The `init-script` supports a number of additional configuration parameters that you may fine useful. All configuration options (required and optional) are detailed below:
| DEVELOCITY_URL | :white_check_mark: | the URL of the Develocity server |
| DEVELOCITY_ALLOW_UNTRUSTED_SERVER | | allow communication with an untrusted server; set to _true_ if your Develocity instance is using a self-signed certificate |
| DEVELOCITY_ENFORCE_URL | | enforce the configured Develocity URL over a URL configured in the project's build; set to _true_ to enforce publication of build scans to the configured Develocity URL |
| DEVELOCITY_PLUGIN_VERSION | :white_check_mark: | the version of the [Develocity Gradle plugin](https://docs.gradle.com/enterprise/gradle-plugin/) to apply |
| DEVELOCITY_CCUD_PLUGIN_VERSION | | the version of the [Common Custom User Data Gradle plugin](https://github.com/gradle/common-custom-user-data-gradle-plugin) to apply, if any |
| GRADLE_PLUGIN_REPOSITORY_URL | | the URL of the repository to use when resolving the Develocity and CCUD plugins; the Gradle Plugin Portal is used by default |
To publish to https://scans.gradle.com, you must specify in your workflow that you accept the [Gradle Terms of Service](https://gradle.com/terms-of-service).
