supergreen

Faster Rust builds!

• cargo-green: Cargo plugin and $RUSTC_WRAPPER to sandbox, cache & remote exec cargo builds

Goals

• seamlessly build on another machine (with more cores, more cache)
  • support remote builds by setting env DOCKER_HOST= with e.g. ssh://me@beaffy-machine.internal.net
    • Build cache is saved remotely, artifacts are saved locally
    • Tests building happens on remote machine, execution happens on local machine
• seamlessly integrate with normal cargo usage
  • only pull sources from local filesystem
  • produce the same intermediary artefacts as local cargo does
  • fallback to normal, local rustc anytime
    • switching from this wrapper back to local rustc does necessitate a fresh build
• wrap rustc calls in buildkit-like calls (docker, podman)
  • docker
  • podman
  • deps compatibility
    • handle Rust-only deps
    • handle all the other deps (expand this list) (use crater)
      • C deps
      • ...
  • runner compatibility
    • set .dockerignores (to be authoritative on srcs)
  • trace these outputs (STDOUT/STDERR) for debugging
• available as a rustc wrapper through $RUSTC_WRAPPER
• available as a cargo subcommand
  • configuration profiles (user, team, per-workspace, per-crate, CI, ...)
  • seamlessly use current/local rustc version
    • support overriding rustc base image
  • seamlessly use current/local tools (mold, ...)
    • config expressions on top of base image config?
    • just suggest an inline Dockerfile stage?
  • support CRUD-ish operations on local/remotes cache
  • [SEC] support building a crate without it having network access
• integrate with shipping OCI images
• share cache with the World cf. user-wide-cache
  • never rebuild a dep (for a given version of rustc, ...)
  • share cache with other projects on local machine
    • fix WORKDIRs + rewrite paths with remap-path-prefix
  • share cache with CI and team
    • share cache with CI (at least for a single user)
  • [SEC] ensure private deps don't leak through/to cache
  • CLI gives the Dockerfile that cargo install's any crate
• suggest a global cache -faciliting configuration profile
• integrate with cross
  • build for a non-local target

Upstream issues & patches

• rust: Compile a crate from its source archive directly
• cargo: Tell rustc wrappers which envs to pass through to allow env sandboxing
• TODO
  1. buildkit flags to prefix stdout and stderr progress
  2. buildkit flag to disable dockerignore and save disk read
  • --ignore-file (closed) moby/moby#12886
  • --no-ignore-file
  1. docker build support multiple input files
  • --file-part

  • =1 stage per Dockerfile part file

    • order doesn't matter: order is fixed when consolidation happens (internally)
  1. cargo + docker
  • rust-lang/cargo#2644 (comment)

Origins

• PoC originally written in Bash: https://github.com/fenollp/buildxargs/blob/buildx/tryin.sh
• Initial blog post https://fenollp.github.io/faster-rust-builds-docker_host

Hacking

See ./hack/