Multi-platform buildx (linux/amd64 + linux/arm64) races both platforms in
parallel by default. On the 4GB build agent, QEMU-emulated 'dotnet restore'
for arm64 alone spikes to 2-3GB and racing amd64 apt-installs push us into
the OOM Killer ("cannot allocate memory" at build 4/5).
Fix: write a small buildkitd.toml with max-parallelism = 1 and pass it to
'docker buildx create --config'. buildkit now runs stages sequentially so
the two platforms don't step on each other's RSS.
Recreate the builder every run so the config always takes effect.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The build agent cannot reach auth.docker.io from behind the local network,
causing 'docker run tonistiigi/binfmt --install arm64' to fail with a token
fetch timeout.
Fix: three-tier fallback for ARM64 binfmt registration:
1. Skip if /proc/sys/fs/binfmt_misc/qemu-aarch64 already exists.
2. Pull tonistiigi/binfmt via docker.m.daocloud.io mirror.
3. Fall back to qemu-user-static via apt.
Add a post-registration sanity check (arm64 alpine + uname -m) so
misconfigured builders fail fast rather than at buildx invocation time.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
nanxunandClaude Opus 4.8