Merge pull request #1914 from tangency-labs/ci-hybrid-runners

CI: main and merge-queue runs share the work with the self-hosted runner

.github/workflows/ci.yml

@@ -11,6 +11,13 @@
 # the viewport's GPU glue, the graphics dependencies, their scripts or this file); main and
 # nightly always run them. Only main saves the build caches; pull requests restore them.
 # Cross-compilation is opt-in through Run workflow; release builds remain in release.yml.
+# Pushes to main and merge-queue groups use both pools: Clippy, the doc tests and test shards
+# 1-2 run on the self-hosted runner (`self-hosted-fast`, warm build directories via
+# scripts/ci/warm-target.sh), everything else on GitHub's runners. The test archive is built on
+# GitHub's runners: the self-hosted machine has a newer glibc, so its binaries wouldn't start
+# on ubuntu-24.04, while the archive runs there unchanged (same /home/runner/work checkout
+# path). Pull requests, the nightly run and Run workflow use GitHub's runners only; the
+# self-hosted runner refuses any job that isn't a push to main or a merge-queue group.
 name: CI
 
 on:
@@ -156,14 +163,19 @@ jobs:
     name: Native Linux Clippy
     needs: changes
     if: needs.changes.outputs.native == 'true'
-    runs-on: ubuntu-24.04
+    runs-on: ${{ (github.event_name == 'merge_group' || (github.event_name == 'push' && github.ref == 'refs/heads/main')) && 'self-hosted-fast' || 'ubuntu-24.04' }}
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Warm build directory (self-hosted runner)
+        if: runner.environment == 'self-hosted'
+        run: scripts/ci/warm-target.sh clippy
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
-      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+      # The self-hosted runner keeps its build directory and Cargo home instead.
+      - if: runner.environment == 'github-hosted'
+        uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
           key: native-clippy
           save-if: ${{ github.ref == 'refs/heads/main' }}
@@ -224,7 +236,7 @@ jobs:
   tests:
     name: Native Linux tests (${{ matrix.shard }}/4)
     needs: [changes, build-tests]
-    runs-on: ubuntu-24.04
+    runs-on: ${{ ((github.event_name == 'merge_group' || (github.event_name == 'push' && github.ref == 'refs/heads/main')) && matrix.shard <= 2) && 'self-hosted-fast' || 'ubuntu-24.04' }}
     timeout-minutes: 60
     strategy:
       fail-fast: false
@@ -380,7 +392,7 @@ jobs:
     name: Doc tests
     needs: changes
     if: needs.changes.outputs.native == 'true'
-    runs-on: ubuntu-24.04
+    runs-on: ${{ (github.event_name == 'merge_group' || (github.event_name == 'push' && github.ref == 'refs/heads/main')) && 'self-hosted-fast' || 'ubuntu-24.04' }}
     timeout-minutes: 45
     env:
       CARGO_INCREMENTAL: "0"
@@ -389,8 +401,13 @@ jobs:
       SCCACHE_IGNORE_SERVER_IO_ERROR: "1"
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Warm build directory (self-hosted runner)
+        if: runner.environment == 'self-hosted'
+        run: scripts/ci/warm-target.sh doc-tests
       - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+      # The self-hosted runner keeps its build directory and Cargo home instead.
+      - if: runner.environment == 'github-hosted'
+        uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
           key: doc-tests
           save-if: ${{ github.ref == 'refs/heads/main' }}