# ctrl/Dockerfile.example

## Naming

EXAMPLE — a component image. Copy, rename, replace. Named like the manifest it feeds and the resource it becomes:

```
ctrl/Dockerfile.api   ->  image <cluster>-api  ->  image: in k8s/base/api.yaml
```

That image string is the ONLY thing connecting the three. Nothing checks it; a typo shows up as a pod stuck in ImagePullBackOff pulling from the public index, which reads like a network problem and is not one.

## COPY paths are repo-root relative (the one that catches everyone)

The Tiltfile passes two paths with DIFFERENT bases, in adjacent arguments:

```
context='..'                 the REPO ROOT   (the Tiltfile is in ctrl/)
dockerfile='Dockerfile.api'  relative to the TILTFILE, so ctrl/Dockerfile.api
```

So every COPY is resolved against the repo root, NOT against the Dockerfile's directory. A file sitting right beside it is still reached as `ctrl/`:

```
COPY ctrl/nginx.conf /etc/nginx/conf.d/default.conf     # correct
COPY nginx.conf      /etc/nginx/conf.d/default.conf     # fails — no such file
```

Nothing warns you. The build just cannot find a file that is visibly there.

## Dependency layer

Dependencies first, in their own layer: they change far less often than the code, so a source edit does not reinstall them on every rebuild.

## live_update

The sync in the Tiltfile's `docker_build` must land where this image expects it:

```
live_update=[sync('../api', '/app/api')]
```

matches `COPY api/ ./api/` with `WORKDIR /app`. If the two disagree, Tilt syncs into a path nothing reads and the container keeps serving the built copy — edits appear to do nothing, with no error anywhere.