# Deploy arcade-eval reference MCP server to backstage k8s

**Date:** 2026-06-22
**Status:** Approved — implementing

## Goal

Replace the ephemeral cloudflared **quick tunnel** (used to register the
`arcade-eval-ref` server with the self-hosted Arcade engine) with a permanent
in-cluster deployment on `backstage-wus2-v4`. The engine then reaches the server
over stable cluster DNS instead of a `trycloudflare.com` URL that dies on restart.

Relevant eval categories: cat-4 (custom server dev), cat-8 (deployment), cat-9 (DX).

## Architecture / data flow

```
Arcade engine (ns: arcade)  ──HTTP /worker/*──▶  Service arcade-eval-ref (ns: arcade-eval-ref)
   registered as type "Arcade"                       └─▶ Deployment: python:3.12 running
   URI = http://arcade-eval-ref.arcade-eval-ref            mcp_server.server over HTTP :8000
        .svc.cluster.local:8000                           (echo / add / whoami)
   Secret = ARCADE_WORKER_SECRET  ◀── same value ──▶  env ARCADE_WORKER_SECRET (SealedSecret)
```

### Runtime facts (verified by introspecting `arcade-mcp-server` 1.17)

- `app.run()` honors env overrides via `_get_configuration_overrides()`:
  `ARCADE_SERVER_TRANSPORT=http`, `ARCADE_SERVER_HOST=0.0.0.0`, `ARCADE_SERVER_PORT=8000`.
  So the hardcoded `127.0.0.1` in `server.py`'s `__main__` is overridden at runtime —
  **no `server.py` change needed.**
- `ARCADE_WORKER_SECRET` (settings alias `arcade.server_secret`) → worker routes mount at
  `/worker/*` (what the engine calls); MCP also served at `/mcp`. FastAPI app, port 8000.

## Components

### 1. `arcade-eval` repo (branch off `main`)

- **`lib/mcp_server/Dockerfile`** — `python:3.12-slim`, `pip install .` (pulls
  `arcade-mcp-server` + `httpx`), `ENV` transport/host/port, non-root user, `EXPOSE 8000`,
  `CMD ["python","-m","mcp_server.server"]`.
- **`.github/workflows/build-push-acr.yml`** — adapted from `servicetitan/mem0`. Pushes
  `servicetitandev.azurecr.io/arcade-eval-ref:1.0.<run_number>`. Login via repo secrets
  `ACR_DEV_USERNAME` / `ACR_DEV_PASSWORD`. Triggers: `workflow_dispatch` + push to `main`
  filtered to `lib/mcp_server/**`.

### 2. `k8s-backstage-v2` repo (branch off `master`)

New dir **`apps/mcp/arcade-eval-ref/`** (Flux's `apps` Kustomization recursively applies
everything under `apps/`; no per-dir `kustomization.yaml`):

- **`namespace.yaml`** — ns `arcade-eval-ref` (labels per repo convention, `team: infra`).
- **`server.yaml`** — plain `Deployment` (image
  `servicetitandev.azurecr.io/arcade-eval-ref:1.0.1`; no imagePullSecret — the cluster has
  native ACR pull, confirmed by other `apps/mcp/*` servers; `ARCADE_WORKER_SECRET` from
  secretRef; TCP probes; modest resources) + `Service` (ClusterIP, 8000→8000).
- **`sealedsecret.yaml`** — `arcade-eval-ref-worker-secret`, key `ARCADE_WORKER_SECRET`,
  **strict** scope, sealed offline with `kubeseal --cert <backstage-wus2-v4 public cert>`.

## Manual steps after merge

1. Add `ACR_DEV_USERNAME` / `ACR_DEV_PASSWORD` repo secrets to `arcade-eval`.
2. `workflow_dispatch` (or merge to `main`) to build/push the image — first run = tag `1.0.1`.
3. Merge the k8s branch; Flux applies the namespace/secret/deployment.
4. Dashboard → **Add Server → Arcade**, URI
   `http://arcade-eval-ref.arcade-eval-ref.svc.cluster.local:8000`, Secret = the worker secret
   plaintext (stored git-ignored at `results/arcade-eval-ref-worker-secret.txt`); re-point the
   `zeb-gateway-test` gateway's ref tools at it and drop the tunnel. Delete the plaintext file
   afterward.

## Out of scope (YAGNI)

No ingress (internal-only ClusterIP), no HPA, no PodMonitor/metrics (separate cat-5 work),
single replica.