# go-cache-plugin

Build repo for [`tailscale/go-cache-plugin`](https://github.com/tailscale/go-cache-plugin),
a `GOCACHEPROG` implementation that backs the Go build cache with S3. Upstream
publishes no releases, so this repo pins a commit via the `tool` directive in
`go.mod` and ships the static binary as a Gitea release.

No source of its own. To move to a newer upstream commit:

```sh
go get -tool github.com/tailscale/go-cache-plugin/cmd/go-cache-plugin@<commit>
make test
```

## Build

```sh
make build   # dist/go-cache-plugin, CGO_ENABLED=0, stripped
make test    # builds the binary, then drives a real `go build` through it
```

## Use

Point it at the estate's Ceph RGW, which needs both a custom endpoint and
path-style addressing:

```sh
export GOCACHEPROG="go-cache-plugin \
  --cache-dir=$HOME/.cache/go-cache-plugin \
  --bucket=go-build-cache \
  --region=default \
  --s3-endpoint-url=https://s3.ceph.unkin.net \
  --s3-path-style"
go build ./...
```

Credentials come from the usual `AWS_ACCESS_KEY_ID`/`AWS_SECRET_ACCESS_KEY`
environment. Every flag also has a `GOCACHE_*` environment equivalent — see
`go-cache-plugin help environment`. Add `--metrics` to print cache hit rates at
exit, and `--expiry` to age entries out.

For a shared cache daemon, run `go-cache-plugin serve --plugin <port>` once and
have each build use `go-cache-plugin connect <port>` as its `GOCACHEPROG`.

## Container image

`artifactapi.k8s.syd1.au.unkin.net/docker-internal/go-cache-plugin`, built and
pushed on tag. Distroless static, nonroot, no shell. `make docker` builds it
locally.

The image carries only the public CA bundle, so a `serve`-mode Deployment must
mount the internal CA and point Go at it:

```yaml
env:
  - name: SSL_CERT_DIR
    value: /etc/ssl/internal
```

`s3.ceph.unkin.net` is issued by `unkin.net Intermediate Authority`; without
that mount the S3 client fails with `x509: certificate signed by unknown
authority`.

## CI

Woodpecker steps fetch the released binary:

```yaml
commands:
  - curl -fsSLo /usr/local/bin/go-cache-plugin https://git.unkin.net/unkin/go-cache-plugin/releases/download/v0.1.0/go-cache-plugin-linux-amd64
  - chmod +x /usr/local/bin/go-cache-plugin
```

## Release

`make patch|minor|major` tags and pushes; the tag pipeline builds
`linux/amd64` and `linux/arm64`, attaches them with `sha256sums.txt`, and
pushes the container image tagged with the git tag and `latest`.