Summary

Currently our Docker builds use QEMU emulation for ARM64 builds (via docker/setup-qemu-action). This is slow—ARM builds under QEMU can be 5-10x slower than native execution.

Proposed Solution

Split each multi-arch build into two parallel jobs running on native architecture runners, then combine with a manifest:

Build Phase (parallel per image)

• AMD64: Run on ubuntu-latest (x86_64), push image with -amd64 suffix
• ARM64: Run on ubuntu-24.04-arm (native ARM runner), push image with -arm64 suffix

Manifest Phase (after builds complete)

Use docker buildx imagetools create to combine the arch-specific images into a single multi-arch manifest:

- name: Create multi-arch manifest
  run: |
    docker buildx imagetools create -t $QUAY_REPO:tag \
      $QUAY_REPO:tag-amd64 \
      $QUAY_REPO:tag-arm64

Benefits

• Faster builds: Native ARM execution vs QEMU emulation
• Better parallelism: Both arches build simultaneously
• More reliable: QEMU can have compatibility issues with some packages

Affected Jobs

All multi-arch build jobs in .github/workflows/docker.yml:

• build-baseimage
• build-core
• build-derivatives (assemble, classify, phylo)
• build-mega

Considerations

• GitHub ARM runners may have different pricing/availability
• Need to handle the manifest creation step carefully for PRs (where we don't push)
• Cache strategy may need adjustment for per-arch caches

References

• GitHub ARM runners announcement
• Docker multi-platform build strategies