# 📦 Self-Hosted Registry & Build Pipeline

> [!NOTE]
> Docker images are built and hosted in-fleet rather than pulled from Docker Hub/ghcr directly — for every stack opted into this pattern, at runtime.

| | |
|---|---|
| **Registry** | The Git server's own built-in container registry — no separate registry service to run |
| **Trigger** | Weekly schedule, not push-triggered |
| **Rollout** | All 5 Docker hosts converted; the largest has 36 of 41 stacks on this pattern |

## The cheap-check-first build decision

```mermaid
flowchart TD
    Start["Weekly trigger"] --> Check["Cheap digest check<br/>metadata only, no pull"]
    Check --> Match{"Upstream digest ==<br/>fleet registry digest?"}
    Match -->|yes| Nothing["Nothing runs<br/>no pull, no build, no push"]
    Match -->|no| Pull["Pull base images"]
    Pull --> Build["docker compose build --no-cache"]
    Build --> Compare["Compare pre/post image IDs"]
    Compare --> Push["Push what actually changed"]
    Push --> Redeploy["Redeploy via shared<br/>health-check/rollback path"]
```

> [!TIP]
> Most stacks use a minimal wrapper Dockerfile around the upstream image rather than a full clone-and-build-from-source setup — simpler, builds near-instantly, can't break from upstream build tooling, while still achieving the real goal: an in-fleet registry with no direct Docker Hub/ghcr dependency at runtime. A handful of multi-build-image stacks skip the cheap check entirely, since a single "upstream digest" comparison doesn't make sense when there's more than one real upstream involved.

## Deliberate holdouts

Not every stack is on this pattern, and that's a decision, not an oversight:

| Stack type | Why it's held out |
|---|---|
| Complex multi-service upstream builds | Not worth replicating a build process someone else already maintains well |
| A docker-socket-proxy style stack | Simple enough that a custom build adds no value |
| One database service still on `latest` | Deliberately not pinned to this pattern |
| One stack with pre-existing custom Dockerfiles | Left as-is beyond adding image references — its own DB/cache still float on upstream tags directly |

## Trigger discipline

> [!WARNING]
> This is schedule-triggered, not push-triggered. Editing a stack's own Dockerfile doesn't by itself trigger a rebuild — it waits for the next weekly sweep to find the upstream base image has actually changed, or for someone to force a manual run. A deliberate tradeoff: simpler mental model, avoids a rebuild storm on every unrelated commit, at the cost of same-day propagation for an urgent base-image CVE fix.

## Housekeeping

Unused local images get pruned automatically at the end of every build pass — for build-and-push-only stacks, the registry is the source of truth, not whatever happens to be sitting on local disk.

---
Related stacks: [`stacks/platform/gitea/`](../stacks/platform/gitea/), [`stacks/platform/kestra/`](../stacks/platform/kestra/)