feat: adding remote cache config for demo and ci builds

.bazelrc

@@ -2,8 +2,6 @@
 # spawn strategy here.
 common --enable_bzlmod
 
-# Shared disk cache: pass --disk_cache=<path> via CI or user rc.
-# The imported .bazelrc.cache bounds long-lived local cache growth.
 import %workspace%/.bazelrc.cache
 
 # Shared Android flags; each nested module imports this file and opts in locally.

.bazelrc.cache

@@ -1,6 +1,10 @@
-# Shared disk cache configuration for long-lived local caches.
-# The path is deliberately unset; CI or a user rc supplies it.
-# GC bounds limit local growth; the 5m idle collector cannot cap CI uploads.
+build --remote_timeout=30
 
-build --experimental_disk_cache_gc_max_size=4G
-build --experimental_disk_cache_gc_max_age=7d
+# Consume cached actions, publish nothing.
+build:cache-read --remote_upload_local_results=false
+
+# Also publish. For CI only, which builds in a pinned environment.
+build:cache-write --remote_upload_local_results=true
+
+# Machine-local endpoint and token. Never committed.
+try-import %workspace%/.bazelrc.local

.github/actions/flutter-bazel/action.yml

@@ -23,8 +23,23 @@ inputs:
     default: >-
       examples/demo_app examples/no_plugins examples/pub_plugins
       examples/local_plugin/packages/host_app
-  disk-cache:
-    description: Optional disk cache path; passed as --disk_cache to Bazel.
+  cache-mode:
+    description: >-
+      Remote cache mode: `read`, `write`, or empty to disable.
+    required: false
+    default: ''
+  cache-host:
+    description: Remote cache host, without a scheme.
+    required: false
+    default: ''
+  cache-project-id:
+    description: Remote cache project id, used to build the instance name.
+    required: false
+    default: ''
+  cache-token:
+    description: >-
+      Cache token whose scope matches `cache-mode`. Any empty cache input
+      disables the cache, which is what fork pull requests get.
     required: false
     default: ''
 
@@ -79,11 +94,28 @@ runs:
         test --test_output=errors
         RC
 
-    - name: Bazel disk cache
-      if: inputs.disk-cache != ''
+    - name: Remote cache
+      if: >-
+        inputs.cache-mode != '' && inputs.cache-token != ''
+        && inputs.cache-host != '' && inputs.cache-project-id != ''
       shell: bash
+      env:
+        CACHE_MODE: ${{ inputs.cache-mode }}
+        BAZEL_CACHE_BAZEL_REMOTE_CACHE_HOST: ${{ inputs.cache-host }}
+        BAZEL_CACHE_BAZEL_PROJECT_ID: ${{ inputs.cache-project-id }}
+        BAZEL_CACHE_BAZEL_REMOTE_CACHE_TOKEN: ${{ inputs.cache-token }}
       run: |
-        echo "build --disk_cache=${{ inputs.disk-cache }}" >> "$HOME/.bazelrc"
+        set -euo pipefail
+        case "$CACHE_MODE" in
+          read|write) ;;
+          *) echo "unknown cache-mode: $CACHE_MODE" >&2; exit 1 ;;
+        esac
+        cat >> "$HOME/.bazelrc" <<RC
+        build --config=cache-$CACHE_MODE
+        build --remote_cache=grpcs://${BAZEL_CACHE_BAZEL_REMOTE_CACHE_HOST}
+        build --remote_instance_name=${BAZEL_CACHE_BAZEL_PROJECT_ID}
+        build --remote_cache_header='Authorization=Bearer ${BAZEL_CACHE_BAZEL_REMOTE_CACHE_TOKEN}'
+        RC
 
     # NDK 28+ avoids 4 KB-aligned .so segments that fail on 16 KB-page devices.
     - name: Select the NDK

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ env:
   # Bazelisk release assets are mutable; verify their bytes before execution.
   BAZELISK_SHA256_LINUX_AMD64: 5a408715e932c0250d28bd84555f12edbf70117de42f9181691c736eacc4a992
   BAZELISK_SHA256_DARWIN_ARM64: cee851f726789227d5561004e9904a52be45c3efb56f8b38b6993d6adbaa0409
-  BAZEL_CACHE_KEY: bazel-cache-macos-arm64
+  BAZEL_CACHE_MODE: ${{ github.event_name == 'pull_request' && 'write' || '' }}
 
 jobs:
   lint:
@@ -54,27 +54,13 @@ jobs:
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
-      - name: Shared disk cache path
-        shell: bash
-        run: echo "BAZEL_CACHE_DIR=$RUNNER_TEMP/bazel_disk_cache" >> "$GITHUB_ENV"
-
-      - name: Restore shared disk cache
-        if: github.event_name == 'pull_request'
-        id: restore
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # actions/cache v6.1.0
-        with:
-          path: ${{ env.BAZEL_CACHE_DIR }}
-          key: ${{ env.BAZEL_CACHE_KEY }}-${{ github.run_id }}-${{ github.run_attempt }}
-          restore-keys: ${{ env.BAZEL_CACHE_KEY }}-
-
       - uses: ./.github/actions/flutter-bazel
         with:
           flutter-version: ${{ env.FLUTTER_VERSION }}
           flutter-sha256: ${{ env.FLUTTER_SHA256 }}
           bazelisk-version: ${{ env.BAZELISK_VERSION }}
           bazelisk-sha256: ${{ env.BAZELISK_SHA256_DARWIN_ARM64 }}
           pub-get: ''
-          disk-cache: ${{ env.BAZEL_CACHE_DIR }}
 
       - name: bazel test //...
         run: |
@@ -121,19 +107,6 @@ jobs:
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
-      - name: Shared disk cache path
-        shell: bash
-        run: echo "BAZEL_CACHE_DIR=$RUNNER_TEMP/bazel_disk_cache" >> "$GITHUB_ENV"
-
-      - name: Restore shared disk cache
-        if: github.event_name == 'pull_request'
-        id: restore
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # actions/cache v6.1.0
-        with:
-          path: ${{ env.BAZEL_CACHE_DIR }}
-          key: ${{ env.BAZEL_CACHE_KEY }}-${{ github.run_id }}-${{ github.run_attempt }}
-          restore-keys: ${{ env.BAZEL_CACHE_KEY }}-
-
       - uses: ./.github/actions/flutter-bazel
         with:
           flutter-version: ${{ env.FLUTTER_VERSION }}
@@ -142,7 +115,10 @@ jobs:
           bazelisk-sha256: ${{ env.BAZELISK_SHA256_DARWIN_ARM64 }}
           # Only this example's app module; local_plugin's lives in a subdirectory.
           pub-get: ${{ matrix.name == 'local_plugin' && 'examples/local_plugin/packages/host_app' || matrix.directory }}
-          disk-cache: ${{ env.BAZEL_CACHE_DIR }}
+          cache-mode: ${{ matrix.name == 'demo_app' && env.BAZEL_CACHE_MODE || '' }}
+          cache-host: ${{ matrix.name == 'demo_app' && secrets.BAZEL_CACHE_HOST || '' }}
+          cache-project-id: ${{ matrix.name == 'demo_app' && secrets.BAZEL_CACHE_PROJECT_ID || '' }}
+          cache-token: ${{ matrix.name == 'demo_app' && secrets.BAZEL_CACHE_TOKEN_RW || '' }}
 
       # Hash gate builds the APKs below; tests run their target guards.
       - name: bazel test //...
@@ -169,20 +145,10 @@ jobs:
 
       - name: Report cache statistics
         if: always()
-        env:
-          REQUIRE_CACHE_HITS: ${{ matrix.name == 'demo_app' && steps.restore.outputs.cache-matched-key != '' }}
         run: |
-          args=(bazel_example_test_${{ matrix.name }}.log bazel_example_hash_${{ matrix.name }}.log)
-          if [[ "$REQUIRE_CACHE_HITS" == "true" ]]; then args+=(--require-hits); fi
-          python3 tools/ci/cache_stats.py "${args[@]}"
-
-      # GitHub eviction and one saver enforce quota; keep main cold so the hash gate proves reproducibility.
-      - name: Save shared disk cache
-        if: github.event_name == 'push' && github.ref == 'refs/heads/main' && matrix.name == 'demo_app'
-        uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # actions/cache v6.1.0
-        with:
-          path: ${{ env.BAZEL_CACHE_DIR }}
-          key: ${{ env.BAZEL_CACHE_KEY }}-${{ github.run_id }}-${{ github.run_attempt }}
+          python3 tools/ci/cache_stats.py \
+            bazel_example_test_${{ matrix.name }}.log \
+            bazel_example_hash_${{ matrix.name }}.log
 
   gate:
     name: Hash table fully claimed

.gitignore

@@ -14,6 +14,8 @@
 # Smooth app fixture clone. See docs/package-recipes.md.
 /third_party/
 
+.bazelrc.local
+
 .DS_Store
 
 # Gradle caches in nested projects.

examples/demo_app/.bazelrc

@@ -1,6 +1,5 @@
 common --enable_bzlmod
 
-# Shared cache settings for long-lived local cache growth.
 import %workspace%/../../.bazelrc.cache
 # Shared Android configuration.
 import %workspace%/../../.bazelrc.android

examples/local_plugin/.bazelrc

@@ -1,6 +1,5 @@
 common --enable_bzlmod
 
-# Shared cache settings for long-lived local cache growth.
 import %workspace%/../../.bazelrc.cache
 # Shared Android configuration.
 import %workspace%/../../.bazelrc.android

examples/no_plugins/.bazelrc

@@ -1,6 +1,5 @@
 common --enable_bzlmod
 
-# Shared cache settings for long-lived local cache growth.
 import %workspace%/../../.bazelrc.cache
 # Shared Android configuration.
 import %workspace%/../../.bazelrc.android

examples/pub_plugins/.bazelrc

@@ -1,6 +1,5 @@
 common --enable_bzlmod
 
-# Shared cache settings for long-lived local cache growth.
 import %workspace%/../../.bazelrc.cache
 # Shared Android configuration.
 import %workspace%/../../.bazelrc.android

tests/consumer/.bazelrc

@@ -1,6 +1,5 @@
 common --enable_bzlmod
 
-# Shared cache settings for long-lived local cache growth.
 import %workspace%/../../.bazelrc.cache
 
 # This consumer fixture requires JDK 17 and does not inherit the root Android