blumeops/docs/how-to/configuration/build-spork-container.md
Erich Blume f9206bf10b
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Build custom Kingfisher container from sporked deploy branch (#318)
## Summary

- Add Dockerfile for Kingfisher built from source (sporked deploy branch)
- Multi-stage: Rust build with Boost/vectorscan, debian-slim runtime
- Switch CronJob from upstream `ghcr.io/mongodb/kingfisher` to `registry.ops.eblu.me/blumeops/kingfisher`
- Add kingfisher to service-versions.yaml (version tracks upstream main SHA)
- Document spork workflow in CLAUDE.md

## Test plan

- [ ] Build container: `mise run container-build-and-release kingfisher 1d37d29`
- [ ] Verify image on registry: `mise run container-list`
- [ ] Update kustomization newTag
- [ ] Sync ArgoCD kingfisher app from branch
- [ ] Trigger manual CronJob and verify scan completes
- [ ] Verify reports on sifaka

Reviewed-on: #318
2026-03-30 06:34:49 -07:00

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3.4 KiB
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---
title: Build a Spork Container
modified: 2026-03-29
last-reviewed: 2026-03-29
tags:
- how-to
- containers
- git
---
# Build a Spork Container
How to build a container image from a [[spork-strategy|sporked]] project with fully-pinned, reproducible inputs.
## Why not use the `deploy` branch directly?
The `deploy` branch is force-pushed on every mirror-sync. Building from `deploy` is not reproducible — the same build a week later fetches different code (or fails because the old commit was garbage collected).
Instead, spork containers use Nix to fetch upstream `main` at a pinned SHA and generate patches from feature branches at pinned SHAs. Both upstream and feature commits are on stable branches that are never force-pushed.
## How the Nix build works
The `default.nix` uses `builtins.fetchGit` (eval-time, network access) to fetch two source trees:
1. **Upstream source** at the pinned `upstreamRev` on `main`
2. **Feature branch source** at the pinned `rev` for each feature
Then a sandboxed `diff -ruN` generates a patch from upstream→feature for each feature branch. `buildRustPackage` applies the patches to the upstream source and builds.
This means:
- The upstream rev persists forever (main only fast-forwards)
- Feature revs are on your branches (you control them)
- No dependency on the `deploy` branch
- Fully reproducible given the same revs
## Prerequisites
- Sporked project set up (see [[create-a-spork]])
- Nix build runs on ringtail (`nix-container-builder` runner)
## Get the SHAs
```fish
cd ~/code/3rd/kingfisher
git fetch origin
# Upstream SHA (main branch)
git rev-parse origin/main
# e.g., 1d37d2983cd4a58c12663dd8df0e79dfe89a5d75
# Feature branch SHAs
git rev-parse origin/feature/upstream/clone-url-base
# e.g., 677c7a5d5fc42b655d38fbf95dc8b814d89ceabb
```
## Update `default.nix`
Edit `containers/kingfisher/default.nix`:
- `version` — short upstream SHA (for container tag)
- `upstreamRev` — full upstream main SHA
- `features[].rev` — full feature branch SHA
If dependencies changed, update `Cargo.lock` too:
```fish
cd ~/code/3rd/kingfisher
git checkout origin/main
cargo update
cp Cargo.lock ~/code/personal/blumeops/containers/kingfisher/Cargo.lock
```
## Build and push
The build is triggered via the standard container build workflow on ringtail's `nix-container-builder` runner, or manually:
```fish
mise run container-build-and-release kingfisher
```
## Update the deployment
1. Update `argocd/manifests/kingfisher/kustomization.yaml` with the new tag
2. Update `service-versions.yaml` if the upstream SHA changed
3. Sync the ArgoCD app
## Note on `CONTAINER_APP_VERSION`
The `default.nix` includes `version` which maps to `CONTAINER_APP_VERSION` for the `container-version-check` hook. For sporked containers this is a git SHA, not a release version. Don't confuse it with an upstream release number.
## Reproducibility
The upstream rev must be an ancestor of each feature rev. If you bump the upstream rev without rebasing your feature branches, the generated patch will conflict and the build fails — which is the correct behavior.
The invariant: **feature revs are descendants of the upstream rev**. Mirror-sync maintains this automatically. You just need to update the revs in `default.nix` after an upgrade.
## See also
- [[create-a-spork]] — initial spork setup
- [[manage-spork-branches]] — feature branch workflow
- [[kingfisher]] — first sporked project