- 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':
- 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.
The Gradle User Home cache key is composed of:
- The current operating system (`RUNNER_OS`)
- The workflow name and Job ID
- A hash of the Job matrix parameters
- The git SHA for the latest commit
Specifically, the cache key is: `${cache-protocol}-gradle|${runner-os}|${workflow-name}-${job-id}[${hash-of-job-matrix}]-${git-sha}`
As such, the cache key is likely to change on each subsequent run of GitHub actions.
This allows the most recent state to always be available in the GitHub actions cache.
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:
- An exact match on OS, workflow, job, matrix and Git SHA
- The most recent entry saved for the same OS, workflow, job and matrix values
- The most recent entry saved for the same OS, workflow and job
- The most recent entry saved for the same OS
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.
GitHub cache entries are not shared between builds on different branches.
This means that each PR branch will have it's own Gradle User Home cache, and will not benefit from cache entries written by other PR branches.
An exception to this is that cache entries written in parent and upstream branches are visible to child branches, and cache entries for the default (`master`/`main`) branch can be read by actions invoked for any other branch.
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.
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/build-result-capture.init.gradle`.
If you are using init scripts for the [Gradle Enterprise Gradle Plugin](https://plugins.gradle.org/plugin/com.gradle.enterprise) like
[`scans-init.gradle` or `gradle-enterprise-init.gradle`](https://docs.gradle.com/enterprise/gradle-plugin/#scans_gradle_com),
you'll need to ensure these files are applied prior to `build-result-capture.init.gradle`.
Since Gradle applies init scripts in alphabetical order, one way to ensure this is via file naming.
If the `gradle-build-action` is configured with an `arguments` input, then Gradle will execute a Gradle build with the arguments provided. NOTE: We recommend using the `gradle-build-action` as a "Setup Gradle" step as described above, with Gradle being invoked via a regular `run` command.
If no `arguments` are provided, the action will not execute Gradle, but will still cache Gradle state and configure build-scan capture for all subsequent Gradle executions.
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 `gradle-build-action` has support for submitting a [GitHub Dependency Graph](https://docs.github.com/en/code-security/supply-chain-security/understanding-your-software-supply-chain/about-the-dependency-graph) snapshot via the [GitHub Dependency Submission API](https://docs.github.com/en/rest/dependency-graph/dependency-submission?apiVersion=2022-11-28).
The dependency graph snapshot is generated via integration with the [GitHub Dependency Graph Gradle Plugin](https://plugins.gradle.org/plugin/org.gradle.github-dependency-graph-gradle-plugin), and saved as a workflow artifact. The generated snapshot files can be submitted either in the same job, or in a subsequent job (in the same or a dependent workflow).
The generated dependency graph snapshot reports all of the dependencies that were resolved during a build execution, and is used by GitHub to generate [Dependabot Alerts](https://docs.github.com/en/code-security/dependabot/dependabot-alerts/about-dependabot-alerts) for vulnerable dependencies, as well as to populate the [Dependency Graph insights view](https://docs.github.com/en/code-security/supply-chain-security/understanding-your-software-supply-chain/exploring-the-dependencies-of-a-repository#viewing-the-dependency-graph).
| `generate-and-submit` | As per `generate`, but any generated dependency graph snapshots will be submitted at the end of the job. |
| `download-and-submit` | Download any previously saved dependency graph snapshots, submitting them via the Dependency Submission API. This can be useful to collect all snapshots in a matrix of builds and submit them in one step. |
Example of a simple workflow that generates and submits a dependency graph:
The `contents: write` permission is not required to generate the dependency graph, but is required in order to submit the graph via the GitHub API. This permission will need to be explicitly enabled in the workflow file for dependency graph submission to succeed.
> [!IMPORTANT]
> The above configuration will work for workflows that run as a result of commits to a repository branch,
> but not when a workflow is triggered by a PR from a repository fork.
> This is because the `contents: write` permission is not available when executing a workflow
> for a PR submitted from a forked repository.
> For a configuration that supports this setup, see [Dependency Graphs for pull request workflows](#dependency-graphs-for-pull-request-workflows).
### Integrating the `dependency-review-action`
The GitHub [dependency-review-action](https://github.com/actions/dependency-review-action) helps you
understand dependency changes (and the security impact of these changes) for a pull request.
For the `dependency-review-action` to succeed, it must run _after_ the dependency graph has been submitted for a PR.
When using `generate-and-submit`, dependency graph files are submitted at the end of the job, after all steps have been
executed. For this reason, the `dependency-review-action` must be executed in a dependent job,
and not as a subsequent step in the job that generates the dependency graph.
Example of a pull request workflow that executes a build for a pull request and runs the `dependency-review-action`:
```yaml
name: PR check
on:
pull_request:
permissions:
contents: write
# Note that this permission will not be available if the PR is from a forked repository
At times it is helpful to limit the dependencies reported to GitHub, in order to security alerts for dependencies that don't form a critical part of your product.
For example, a vulnerability in the tool you use to generate documentation is unlikely to be as important as a vulnerability in one of your runtime dependencies.
There are a number of techniques you can employ to limit the scope of the generated dependency graph:
- [Don't generate a dependency graph for all Gradle executions](#choosing-which-gradle-invocations-will-generate-a-dependency-graph)
- [For a Gradle execution, filter which Gradle projects and configurations will contribute dependencies](#filtering-which-gradle-configurations-contribute-to-the-dependency-graph)
> Ideally, all dependencies involved in building and testing a project will be extracted and reported in a dependency graph.
> These dependencies would be assigned to different scopes (eg development, runtime, testing) and the GitHub UI would make it easy to opt-in to security alerts for different dependency scopes.
> However, this functionality does not yet exist.
### Choosing which Gradle invocations will generate a dependency graph
Once you enable the dependency graph support for a workflow job (via the `dependency-graph` parameter), dependencies will be collected and reported for all subsequent Gradle invocations.
If you have a Gradle build step that you want to exclude from dependency graph generation, you can set the `GITHUB_DEPENDENCY_GRAPH_ENABLED` environment variable to `false`.
Instead of generating a dependency graph from your existing CI workflow, it's possible to create a separate dedicated workflow (or Job) that is solely intended for generating a dependency graph.
Such a workflow will still need to execute Gradle, but can do so in a way that is targeted at resolving exactly the dependencies required.
This `contents: write` permission is not available for any workflow that is triggered by a pull request submitted from a forked repository, since it would permit a malicious pull request to make repository changes.
Because of this restriction, it is not possible to `generate-and-submit` a dependency graph generated for a pull-request that comes from a repository fork. In order to do so, 2 workflows will be required:
1. The first workflow runs directly against the pull request sources and will generate the dependency graph snapshot.
2. The second workflow is triggered on `workflow_run` of the first workflow, and will submit the previously saved dependency snapshots.
Note: when `download-and-submit` is used in a workflow triggered via [workflow_run](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_run), the action will download snapshots saved in the triggering workflow.
### Integrating `dependency-review-action` for pull request workflows
The GitHub [dependency-review-action](https://github.com/actions/dependency-review-action) helps you
understand dependency changes (and the security impact of these changes) for a pull request.
To integrate the `dependency-review-action` into the pull request workflows above, a separate workflow should be added.
This workflow will be triggered directly on `pull_request`, but will need to wait until the dependency graph results are
submitted before the dependency review can complete. How long to wait is controlled by the `retry-on-snapshot-warnings` input parameters.
Here's an example of a separate "Dependency Review" workflow that will wait for 10 minutes for the PR check workflow to complete.
```yaml
name: dependency-review
on:
pull_request:
permissions:
contents: read
pull-requests: write
jobs:
dependency-review:
runs-on: ubuntu-latest
steps:
- name: 'Dependency Review'
uses: actions/dependency-review-action@v3
with:
retry-on-snapshot-warnings: true
retry-on-snapshot-warnings-timeout: 600
```
The `retry-on-snapshot-warnings-timeout` (in seconds) needs to be long enough to allow the entire `run-build-and-generate-dependency-snapshot` and `submit-dependency-snapshot` workflows (above) to complete.
The `gradle-build-action` provides support for injecting and configuring the Gradle Enterprise 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.
## Enabling Gradle Enterprise injection
In order to enable Gradle Enterprise for your build, you must provide the required configuration via environment variables.
This configuration will automatically apply `v3.15.1` of the [Gradle Enterprise Gradle plugin](https://docs.gradle.com/enterprise/gradle-plugin/), and publish build scans to https://ge.gradle.org.
Note that the `ge.gradle.org` server requires authentication in order to publish scans. The provided `GRADLE_ENTERPRISE_ACCESS_KEY` isn't required by the Gradle Enterprise injection script,
but will be used by the GE plugin in order to authenticate with the server.
## Configuring Gradle Enterprise injection
The `init-script` supports a number of additional configuration parameters that you may fine useful. All configuration options (required and optional) are detailed below:
| GRADLE_ENTERPRISE_URL | :white_check_mark: | the URL of the Gradle Enterprise server |
| GRADLE_ENTERPRISE_ALLOW_UNTRUSTED_SERVER | | allow communication with an untrusted server; set to _true_ if your Gradle Enterprise instance is using a self-signed certificate |
| GRADLE_ENTERPRISE_ENFORCE_URL | | enforce the configured Gradle Enterprise URL over a URL configured in the project's build; set to _true_ to enforce publication of build scans to the configured Gradle Enterprise URL |
| GRADLE_ENTERPRISE_PLUGIN_VERSION | :white_check_mark: | the version of the [Gradle Enterprise Gradle plugin](https://docs.gradle.com/enterprise/gradle-plugin/) to apply |
| GRADLE_ENTERPRISE_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_ENTERPRISE_PLUGIN_REPOSITORY_URL | | the URL of the repository to use when resolving the GE and CCUD plugins; the Gradle Plugin Portal is used by default |
Gradle Enterprise injection is designed to enable publishing of build scans to a Gradle Enterprise instance,
and is not suitable for publishing to the public Build Scans instance (https://scans.gradle.com).
In order to publish Build Scans to scans.gradle.com, you need to:
- Apply the Gradle Enterprise plugin to your build configuration ([see docs](https://docs.gradle.com/enterprise/get-started/#applying_the_plugin))
- Programmatically accept the Terms of Service for scans.gradle.com ([see docs](https://docs.gradle.com/enterprise/gradle-plugin/#connecting_to_scans_gradle_com))
- Execute the build with `--scan` or configure your build with `publishAlways()` ([see docs](https://docs.gradle.com/enterprise/get-started/#always_publishing_a_build_scan))
