Chunked blob uploads kept the in-progress session in process memory keyed by
upload UUID, so the POST/PATCH/PUT of a single `docker push` had to land on the
same replica. In production the API runs at minReplicas 2 with no session
affinity, so a real push (which streams the layer via PATCH then finalises with
PUT) intermittently 404s with BLOB_UPLOAD_UNKNOWN when chunks hit a replica that
never saw the POST.
- Stage chunked uploads in object storage under uploads/<uuid> instead of an
in-memory temp file. The UUID travels in the Location URL handed to the
client, so any replica reconstructs the staging key with no shared in-process
state. Finalise streams the staged bytes plus any trailing PUT body through
the CAS in one pass; monolithic uploads are unchanged.
- Support DELETE of an in-progress upload (cancel) by dropping its staging
object.
- Reap abandoned staging objects in the GC (uploads/ older than 24h) via a new
S3 ListStaleObjects, so cancelled/interrupted pushes don't leak.
Verified by splitting a single push across two instances sharing one
Postgres+MinIO: POST->A, PATCH->B, PUT->A finalises and the blob pulls back
byte-identical from both. The dockerised e2e suite still passes.
## Why
Local `docker` repos had no write path — the `/v2` Docker Registry API only proxied to upstreams. This makes a local docker repo a genuine container registry so `docker push`/`docker pull` (and podman/skopeo/buildah) work against it directly, matching the project principle that a local repo is *the real thing* rather than a mirror.
## Changes
- Implement the Docker Registry HTTP API V2 read/write half for local docker repos: blob uploads (monolithic and chunked POST/PATCH/PUT), manifest push, `tags/list`, and blob/manifest GET/HEAD.
- Store blobs and manifests through the existing content-addressable store; keep a `local_files` reference per (repo, image) so the GC does not reap them. Tags are mutable (`UpsertLocalFile`); digests and blobs are immutable.
- Dispatch `/v2` reads to the local handler for local docker repos and fall through to the upstream proxy otherwise; writes are local-docker only.
- Add `UpsertLocalFile` for mutable tag references.
- Cover the push/pull round-trip with a dockerised e2e test and unit-test the registry path parser. Document the registry in the README.
## Verification
- `scripts/docker-e2e.sh` passes, including the new `TestLocalDockerPushPull`.
- Verified a real end-to-end round-trip with skopeo against a live instance: pushed `hello-world`, pulled it back, loaded it into the docker daemon, and ran it successfully.
Reviewed-on: #103
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>
unkinben