fix: block single-arch images from reaching production#103
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A hand-pushed evcc/optimizer:latest carrying only a linux/arm64 manifest took production down: Container Apps nodes are amd64, found no matching manifest, and every replica looped in ImagePullBackOff. Deploy now inspects the tag before touching Azure and fails with an explicit error when linux/amd64 is missing. The index template covers multi-platform tags; single-platform tags publish a bare manifest, for which that template fails and the fallback reads the config blob. docker-build builds linux/amd64,linux/arm64. Buildx cannot load a manifest list into the local image store, so it pushes directly and the separate docker-push target is gone. Local iteration moves to docker-build-local, which is host-arch and never pushes; the default target uses it, so a bare make no longer publishes anything. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Why
evcc/optimizer:latestpushed by hand on 2026-07-24T13:26Z carried only alinux/arm64manifest. Azure Container Apps nodes are amd64, found no matching manifest, and every replica looped inImagePullBackOff—optimizer.evcc.iowas down untillatestwas rebuilt multi-arch. Every earlier tag wasamd64+arm64; there was noPublish Dockerrun that day, so the buildx path was bypassed.Nothing in the pipeline noticed.
deploy.ymldeployed the broken tag to 100% traffic a minute after the push.What
deploy.yml— inspects the tag before touching Azure, fails with an explicit error iflinux/amd64is absent. Multi-platform tags publish an index (.Manifest.Manifests); single-platform tags publish a bare manifest, for which that template exits 1 and the fallback reads the config blob.Makefile—docker-buildnow buildslinux/amd64,linux/arm64(override viaDOCKER_PLATFORMS).Behaviour changes worth reviewing
Buildx cannot load a manifest list into the local image store, so a multi-platform tag only exists once pushed. Consequences:
docker-buildpushes directly; the separatedocker-pushtarget is gone.docker-build-local— host arch,--load, never pushes.defaultusesdocker-build-local, so a baremakeno longer publishes anything (previously it built a local image that a latermake docker-pushcould ship single-arch — the exact outage path).Verification
Check logic run against the real registry, all three manifest shapes:
latest(multi-arch)linux/amd64 linux/arm64eacd365…(single-arch amd64)linux/amd64sha256:29a91f79…(the outage image)linux/arm64deploy.ymlparses as YAML with the step in the right position; Actions leaves the bare Go-template braces alone.make -nfordefault,docker-build,docker-runall expand as intended.Not covered: the check reads the tag at deploy time, so a tag overwritten between check and pull still slips through. Digest-pinned deploys would close that; out of scope here.
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