name: Shadow — Shared CPU Spike

# OS-49 Phase 2 / PR 1 — non-blocking spike. Runs `cargo check` on the
# nv-gha-runners shared CPU pool (`linux-{amd64,arm64}-cpu8`) with a
# GHA-backed sccache.
#
# Plan, decision thresholds, and results live in the Linear doc attached
# to OS-126 ("OS-126 — Shared CPU spike plan & results"). Dispatch this
# workflow 4–5 times after merge and record numbers there.

on:
  workflow_dispatch:

permissions:
  contents: read
  packages: read

env:
  CARGO_TERM_COLOR: always
  CARGO_INCREMENTAL: "0"
  MISE_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  # Wire sccache (already RUSTC_WRAPPER in mise.toml) to the GHA cache
  # backend instead of the EKS memcached used by ARC.
  SCCACHE_GHA_ENABLED: "true"

jobs:
  rust-check:
    name: cargo check (${{ matrix.runner }})
    strategy:
      fail-fast: false
      matrix:
        runner: [linux-amd64-cpu8, linux-arm64-cpu8]
    runs-on: ${{ matrix.runner }}
    env:
      # Partition the GHA sccache cache per-arch. Without this, matrix jobs
      # collide on the same cache key, and the later-starting job's writes
      # fail with 409 Conflict while the earlier one's writes land — leaving
      # subsequent runs with asymmetric and mostly-empty caches.
      # (Run 1 on 2026-04-24 showed amd64 with 0/1062 writes succeeding
      # while arm64 got 575/1064.)
      SCCACHE_GHA_VERSION: ${{ matrix.runner }}
    container:
      image: ghcr.io/nvidia/openshell/ci:latest
      credentials:
        username: ${{ github.actor }}
        password: ${{ secrets.GITHUB_TOKEN }}
    timeout-minutes: 60
    steps:
      - uses: actions/checkout@v4

      - name: Install tools
        run: mise install

      - name: Configure GHA sccache backend
        # Exposes ACTIONS_CACHE_URL / ACTIONS_RUNTIME_TOKEN to subsequent steps
        # so sccache (wrapped around rustc via RUSTC_WRAPPER in mise.toml) can
        # initialize the GHA cache. Without this, sccache fails at startup with
        # "cache url for ghac not found". The action also installs its own
        # sccache binary; harmless since mise's sccache remains on PATH.
        uses: mozilla-actions/sccache-action@7d986dd989559c6ecdb630a3fd2557667be217ad # v0.0.9

      - name: Cache Rust target and registry
        uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2
        with:
          shared-key: shadow-shared-cpu-spike-${{ matrix.runner }}
          cache-directories: .cache/sccache

      - name: cargo check
        run: mise x -- cargo check --workspace --all-targets

      - name: sccache stats
        if: always()
        run: mise x -- sccache --show-stats