Add conditional JDK caching - #1201
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Cache resolved JDK tool-cache entries by exact platform and release identity, with a default-on cache-jdk input and explicit opt-out. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR introduces default-on caching of downloaded JDK installations (cache-jdk, opt-out via cache-jdk: false) and wires that caching into both the setup (restore-before-download) and post-action cleanup (save) flows, independently of dependency/wrapper caching.
Changes:
- Add cache-jdk input (default true) and propagate it through setup orchestration into distribution installers.
- Implement JDK restore/save behavior via a new src/jdk-cache.ts module and invoke it from installers + cleanup post step.
- Update docs/tests and regenerate bundled dist/ artifacts to reflect the new behavior and input.
| File | Description |
|---|---|
| src/setup-java.ts | Reads cache-jdk input and passes it through installer options. |
| src/jdk-cache.ts | New module to restore/save tool-cache-backed JDK installs via Actions cache. |
| src/distributions/local/installer.ts | Adds JDK cache restore path for local jdk-file installs (keyed by content hash). |
| src/distributions/base-models.ts | Extends installer options with cacheJdk. |
| src/distributions/base-installer.ts | Restores JDK cache before download; adds tool-cache path helpers and release identity. |
| src/constants.ts | Adds INPUT_CACHE_JDK constant. |
| src/cleanup-java.ts | Saves dependency cache and/or JDK cache in post step, honoring cache-read-only. |
| README.md | Documents cache-jdk and expands cache-read-only semantics to include JDK caches. |
| package.json | Updates release script to include additional cleanup bundle outputs. |
| action.yml | Adds cache-jdk input with default true; broadens cache-read-only description. |
| tests/setup-java.test.ts | Ensures cacheJdk is propagated and modules aren’t initialized when disabled. |
| tests/jdk-cache.test.ts | New unit tests for JDK cache keying, restore, and save behavior. |
| tests/distributors/base-installer.test.ts | Verifies restore-before-download behavior when cacheJdk is enabled. |
| tests/cleanup-java.test.ts | Adds coverage for saving JDK caches independently and honoring cache-jdk: false. |
| dist/setup/index.js | Regenerated bundle reflecting new input and wiring. |
| dist/setup/971.index.js | Regenerated bundled dependency chunk changes (cache/core exports, etc.). |
| dist/setup/779.index.js | New bundled chunk for jdk-cache + cache-feature. |
| dist/setup/242.index.js | Regenerated bundled JavaBase with JDK caching logic and helpers. |
| dist/setup/19.index.js | Regenerated bundled local installer with JDK cache restore + file hashing. |
| dist/cleanup/314.index.js | New bundled cleanup chunk including saveJdkCaches. |
Review details
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- Files reviewed: 14/21 changed files
- Comments generated: 2
- Review effort level: Lite
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JDK cache benchmark resultsResult: real warm-path benefit, with a storage tradeoff. Across 5 isolated, sequential samples, the candidate reduced median warm setup-java time from 7s to 3s (4s / 57% faster) and median total warm job time from 24s to 18s (6s / 25% faster). The paired warm setup delta was -5s median (range -10s to -2s); all 5 samples favored the candidate. The paired total-job delta was -6s median (range -11s to -1s). Method
Cache behavior and costsEvery candidate cold log reported JDK cache is not found, downloaded Microsoft JDK 17.0.19, and saved the same release-derived key. Every candidate warm log (5/5) explicitly reported JDK cache restored from key; every baseline warm log downloaded the JDK again. Maven dependency and wrapper caches also restored on both variants. The JDK adds 175.3 MiB compressed per JDK identity. Maven dependencies were 154.2 MiB and the wrapper 8.7 MiB per isolated variant, so candidate cache storage was about 338.2 MiB vs 162.9 MiB for baseline (+175.3 MiB / +108% in this case). Candidate cold post-cache time was 3-6s (median 5s) versus 2-6s (median 4s); parallel cache saves and network variance make that 1s median difference inconclusive. Median cold total job time was 50s vs 43s (+7s), but paired deltas ranged from -5s to +11s. For the action steps alone, the paired median cold setup+post overhead was about 2s, versus a 5s paired median warm setup saving, so the feature generally breaks even on the first warm reuse. Using noisier total-job medians gives a break-even around 1-2 warm jobs. All measured jobs still round to one billed Linux minute, so this does not reduce per-job billed minutes in this short workload; it improves latency/runner occupancy. Cache quota pressure and eviction are the main tradeoffs, especially across many OS/architecture/distribution/version identities. With n=5, the approximate 95% paired-mean confidence interval is a 1.5-8.9s warm setup saving and 1.6-10.4s total-job saving. Limitations: one Linux runner image, one JDK distribution/version, small sample, and normal hosted-runner/network variance. The consistent 5/5 restore wins and non-overlapping setup ranges (candidate 2-5s, baseline 7-13s) support a real benefit for downloaded JDKs. Reusable harness: actions/setup-java-benchmarks#10, final benchmark branch commit fe91a0d. Raw JSON/CSV artifacts are attached to each workflow run. |
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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Use one normalized runner OS dimension, reset the internal cache key schema for the unreleased feature, and align documentation, tests, and bundles. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Use the established RUNNER_OS value directly and retain process.platform only as a non-Actions fallback. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Bind each JDK cache key to the installation identity it was computed for, keep post-job saves best-effort per entry, and state the real reuse and verification guarantee in the documentation. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Bring in brace-expansion 5.0.9 (#1202) plus the accompanying dependency metadata cleanup and the java-package contract test update for the README table format. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Rename '## Caching dependencies' to '## Caching' and add a what-gets-cached overview table covering the dependency, wrapper, and JDK caches. Lead with the common 'cache: maven' example and the dependency-cache material, and demote JDK caching into its own subsection. Also corrects the IMPORTANT callout, which implied JDK caching required an explicit opt-in; it is enabled implicitly whenever 'cache' is set. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
- Remove pull-request framing that compared behavior to `main`; state the tool-cache and `jdkfile` behavior directly and unconditionally. - Clarify that the JDK cache is a separate cache *entry* from the dependency and wrapper caches, while its *enablement* is coupled to `cache`, so the opening paragraph agrees with the enablement matrix. - Cite the actions/setup-java-benchmarks repository instead of an open PR and a self-referential PR comment, keeping the measured figures and caveats. - Keep the `cache`/`cache-jdk` matrix only in docs/advanced-usage.md and summarize the rules in prose in README.md to avoid divergence. - Describe the guarantee that a cache key is only saved with the installation it was computed for, instead of documenting inode/size/timestamp internals. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: e2755464-4e83-47b6-ba71-731bb481b418
Summary
Effective cache matrix
Validation
The existing Maven benchmark results still apply because cache: maven implicitly enables JDK caching when cache-jdk is omitted.