kache-action

GitHub Action for kache — a content-addressed Rust build cache.

Installs kache, sets it as RUSTC_WRAPPER, and persists the cache between runs. Works out of the box with GitHub's built-in cache, or with any S3-compatible backend.

Usage

- uses: zondax/kache-action@v1

That's it. This installs kache, sets RUSTC_WRAPPER, and uses GitHub Actions cache to persist artifacts between runs. No configuration needed.

With S3

If you have an S3 bucket (or any S3-compatible storage like MinIO, R2, etc.), the action will use that instead of GitHub's cache:

- uses: zondax/kache-action@v1
  with:
    s3-bucket: my-build-cache
    s3-access-key-id: ${{ secrets.S3_ACCESS_KEY_ID }}
    s3-secret-access-key: ${{ secrets.S3_SECRET_ACCESS_KEY }}

For non-AWS providers, set s3-endpoint:

- uses: zondax/kache-action@v1
  with:
    s3-bucket: my-build-cache
    s3-endpoint: https://minio.internal:9000
    s3-access-key-id: ${{ secrets.S3_ACCESS_KEY_ID }}
    s3-secret-access-key: ${{ secrets.S3_SECRET_ACCESS_KEY }}

Full example

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable

      - uses: zondax/kache-action@v1
        with:
          s3-bucket: my-build-cache
          s3-region: eu-west-1
          s3-access-key-id: ${{ secrets.S3_ACCESS_KEY_ID }}
          s3-secret-access-key: ${{ secrets.S3_SECRET_ACCESS_KEY }}

      - run: cargo build --release
      - run: cargo test
      # Post step runs automatically: saves cache + prints summary

Supported platforms

Runner OS	Architecture
Linux	x64, arm64
macOS	x64, arm64

Cache backends

Backend	When	How
GitHub Actions cache	No S3 configured (default)	Saves/restores the local kache store via @actions/cache. Key is based on OS, arch, and Cargo.lock hash.
S3	s3-bucket is set	Uses kache sync --pull / --push. Supports AWS S3, MinIO, R2, etc.

GitHub Actions cache has a 10 GB limit per repo. For larger projects or shared caches across repos, use S3.

Inputs

Input	Default	Description
version	latest release	Kache version to install
s3-bucket	—	S3 bucket name (enables S3 backend)
s3-region	us-east-1	S3 region
s3-prefix	artifacts	S3 key prefix
s3-endpoint	—	Custom S3 endpoint (MinIO, R2, etc.)
s3-access-key-id	—	S3 access key ID
s3-secret-access-key	—	S3 secret access key
cache-executables	false	Also cache bin/dylib/proc-macro outputs
github-cache	true	Use GitHub Actions cache when S3 is not configured
cache-key-prefix	kache	Prefix for the GitHub Actions cache key
sync	true	Pull remote cache on setup
token	${{ github.token }}	GitHub token for fetching releases and posting PR comments

How it works

Setup step (runs before your build):

1. Downloads the kache binary from GitHub Releases and verifies its SHA256 checksum
2. Sets RUSTC_WRAPPER=kache and exports S3 env vars if configured
3. Restores the cache — either kache sync --pull (S3) or @actions/cache restore (GitHub)

Post step (runs after your build, even on failure):

1. Saves the cache — either kache sync --push (S3) or @actions/cache save (GitHub)
2. Posts a sticky PR comment with hit rate and cache miss breakdown (updated in-place on re-runs)
3. Writes a job summary with cache stats, duration, and a collapsible kache list of all cache entries

On self-hosted runners, the kache binary is cached via @actions/tool-cache so it's only downloaded once per version.

PR comments

On pull requests, the post step posts (or updates) a comment showing:

• Hit rate, local/remote hit counts, and miss count at a glance
• A collapsible table of cache misses sorted by compile time, so you can see which crates are the most expensive to rebuild

The comment is updated in-place on re-runs — no spam. Requires pull-requests: write permission on the token (the default GITHUB_TOKEN has this in most setups).

License

Apache-2.0