chore: remove overlaybd from rchab#43
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Overlaybd was an accelerated-container-image format that rchab converted images into on demand via POST /flyio/v1/buildOverlaybdImage. The platform side of the feature — flyd's ImageRef.Layers handling and the overlaybd snapshotter on hosts — was removed in nomad-firecracker#3341 (merged 2025-05-22). Since then, any flyctl client with [experimental] lazy_load_images = true in fly.toml was producing a silently-broken deploy: rchab would happily convert and return an overlaybd hash, but flaps/flyd ignored the resulting layer manifest. Cut the dead code at the source: - Drop the two overlaybd build stages from the Dockerfile (the accelerated-container-image snapshotter and the libaio/libnl/cmake- based overlaybd build). Drop the runtime apk deps those binaries linked against (libcurl, e2fsprogs-libs, libaio, libnl3, libssl3, zlib, zstd-libs — the base docker:24.0.7-alpine3.19 image supplies what dockerd itself needs). - Delete dockerproxy/overlaybd.go. - Stop registering /flyio/v1/buildOverlaybdImage in main.go. Old flyctl clients with lazy_load_images still set will now get an explicit 404 from rchab. dockerfile_builder.go:312 catches that and warns 'failed to build lazy-loaded image, not using lazy-loading', falling through to a normal image build — strictly better than the silent platform-side breakage they get today. A follow-up PR against flyctl will remove the client-side call path and warn on the lazy_load_images flag so customers know to drop it from fly.toml. Cuts ~90 lines and a couple of minutes off every Dockerfile build.
Added alongside the other overlaybd runtime libs in #32 for overlaybd's ext4 layer construction. Nothing else in the image uses mke2fs/e2fsck/resize2fs/tune2fs.
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Summary
Removes overlaybd support from rchab. The platform side of the feature was removed in
nomad-firecracker#3341(merged 2025-05-22) — flyd no longer understandsImageRef.Layers, and the overlaybd snapshotter is gone from hosts. rchab has been carrying the build machinery and the/flyio/v1/buildOverlaybdImageendpoint as dead weight ever since.Cuts ~90 lines, two multi-stage Docker builds (including a
cmake+ C build with submodules), and a handful of runtimeapkdeps (libaio,libnl3,libssl3,libcurl,e2fsprogs-libs,zlib,zstd-libs) that only existed for the overlaybd binaries.Changes
Dockerfile: dropoverlaybd_snapshotter_buildandoverlaybd_buildstages, the fourCOPY --from=overlaybd_*lines, and the runtime lib deps those binaries linked against. The basedocker:24.0.7-alpine3.19image supplies what dockerd itself needs.dockerproxy/overlaybd.go: delete.dockerproxy/main.go: stop registering/flyio/v1/buildOverlaybdImage.Customer impact
Zero for the common case. The only customers who can hit the removed endpoint are those with
[experimental] lazy_load_images = trueinfly.toml. Today they get a silently broken deploy: rchab converts the image and returns a hash, but flaps/flyd ignores the layer manifest. After this PR:lazy_load_images = true→ POST returns 404 →dockerfile_builder.go:312catches the error, logsfailed to build lazy-loaded image, not using lazy-loading, and falls through to a normal image build. Strictly better than today.Follow-up
Separate PR against
flyctlto removeUseOverlaybd/buildOverlaybdImage/daemon_url_test.gooverlaybd case, and to warn on[experimental] lazy_load_imagesso customers know to drop it fromfly.toml.Test plan
go build ./...passesgo test ./...passes (TestErrorremains green)fly deploy --remote-onlyagainst the new image still works for a Dockerfile deploy (manual bake)