CI: compose disk-cache-disable (Tom #2864) + NL remote cache

.github/actions/setup-nativelink-cloud/action.yaml

@@ -77,7 +77,7 @@ inputs:
 
 outputs:
   enabled:
-    description: "'true' when a user.bazelrc was written, else 'false'."
+    description: "'true' when remote cache or execution is enabled, else 'false'."
     value: ${{ steps.configure.outputs.enabled }}
 
 runs:

.github/workflows/lre.yaml

@@ -20,7 +20,41 @@ concurrency:
   cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
 
 jobs:
+  # Compute whether this diff can affect the LRE example builds. These lanes
+  # build @local-remote-execution//examples, so they are keyed off the LRE
+  # toolchain inputs. Pushes to main always run the full matrix (backstop).
+  changes:
+    name: Compute affected lanes
+    runs-on: ubuntu-24.04
+    outputs:
+      lre: ${{ steps.filter.outputs.lre }}
+    steps:
+      - name: Checkout
+        uses: >- # v6.0.2
+          actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - name: Filter LRE-affecting paths
+        uses: >- # v3.0.2
+          dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36
+        id: filter
+        with:
+          filters: |
+            lre:
+              - 'local-remote-execution/**'
+              - 'MODULE.bazel'
+              - 'MODULE.bazel.lock'
+              - '*.bazelrc'
+              - 'flake.nix'
+              - 'flake.lock'
+              - 'tools/**'
+              - '.github/workflows/lre.yaml'
+              - '.github/actions/**'
+
   local:
+    needs: [changes]
+    if: >-
+      github.ref == 'refs/heads/main'
+      || needs.changes.outputs.lre == 'true'
     strategy:
       fail-fast: false
       matrix:

.github/workflows/native-bazel.yaml

@@ -49,15 +49,8 @@ jobs:
       - name: Free disk space
         uses: ./.github/actions/free-disk
 
-      - name: Setup Bazel
-        uses: >- # v0.19.0
-          bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86
-        with:
-          bazelisk-cache: true
-          repository-cache: true
-          disk-cache: ${{ github.workflow }}-${{ matrix.os }}-bazel-${{ matrix.bazel_version }}
-
       - name: Setup NativeLink Cloud
+        id: setup-nativelink-cloud
         uses: ./.github/actions/setup-nativelink-cloud
         with:
           ci-mode: ${{ vars.NATIVELINK_CI_MODE }}
@@ -72,6 +65,16 @@ jobs:
           # non-Linux runners, so macOS lanes fall back to cache.
           exec: ${{ runner.os == 'Linux' && 'on' || 'off' }}
 
+      - name: Setup Bazel
+        uses: >- # v0.19.0
+          bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86
+        with:
+          bazelisk-cache: true
+          repository-cache: true
+          # Only enable when we don't have remote cache, otherwise it just gets very slow
+          # and enormous
+          disk-cache: ${{ steps.setup-nativelink-cloud.outputs.enabled == 'false'}}
+
       - name: Show Bazel version
         run: bazel --version
 
@@ -119,15 +122,8 @@ jobs:
         with:
           compose-file: src/bin/docker-compose.store-tester.yaml
 
-      - name: Setup Bazel
-        uses: >- # v0.19.0
-          bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86
-        with:
-          bazelisk-cache: true
-          repository-cache: true
-          disk-cache: ${{ github.workflow }}-ubuntu-24.04
-
       - name: Setup NativeLink Cloud
+        id: setup-nativelink-cloud
         uses: ./.github/actions/setup-nativelink-cloud
         with:
           ci-mode: ${{ vars.NATIVELINK_CI_MODE }}
@@ -142,6 +138,16 @@ jobs:
           # non-Linux runners, so macOS lanes fall back to cache.
           exec: ${{ runner.os == 'Linux' && 'on' || 'off' }}
 
+      - name: Setup Bazel
+        uses: >- # v0.19.0
+          bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86
+        with:
+          bazelisk-cache: true
+          repository-cache: true
+          # Only enable when we don't have remote cache, otherwise it just gets very slow
+          # and enormous
+          disk-cache: ${{ steps.setup-nativelink-cloud.outputs.enabled == 'false'}}
+
       - name: Run Store tester with sentinel
         run: |
           bazel run //:redis_store_tester \

.github/workflows/nix.yaml

@@ -157,8 +157,45 @@ jobs:
           nativelink_attic_token: ${{ secrets.NATIVELINK_ATTIC_TOKEN }}
           nix_name: .#${{ matrix.test-name }}-with-nativelink-test
 
+  # Compute which lanes this diff can affect. The rbe-* lanes validate
+  # "does this toolchain still build through NativeLink", so they are keyed
+  # off the toolchain/LRE configuration inputs they consume. Pushes to main
+  # always run the full matrix (backstop), so no change can merge without
+  # the complete matrix running against it.
+  changes:
+    name: Compute affected lanes
+    runs-on: ubuntu-24.04
+    outputs:
+      toolchain: ${{ steps.filter.outputs.toolchain }}
+    steps:
+      - name: Checkout
+        uses: >- # v6.0.2
+          actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - name: Filter toolchain-affecting paths
+        uses: >- # v3.0.2
+          dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36
+        id: filter
+        with:
+          filters: |
+            toolchain:
+              - 'toolchain-examples/**'
+              - 'local-remote-execution/**'
+              - 'MODULE.bazel'
+              - 'MODULE.bazel.lock'
+              - '*.bazelrc'
+              - 'flake.nix'
+              - 'flake.lock'
+              - 'tools/**'
+              - '.github/workflows/nix.yaml'
+              - '.github/actions/**'
+
   # rbe-toolchain is slow because it has many subcommands, so split it out
   generate-rbe-commands:
+    needs: [changes]
+    if: >-
+      github.ref == 'refs/heads/main'
+      || needs.changes.outputs.toolchain == 'true'
     runs-on: ubuntu-24.04
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}