add GHA routing regression pipeline skeleton

.github/actions/build-tiles/action.yml

@@ -0,0 +1,43 @@
+name: Build Tiles
+description: >
+  Builds a routable Valhalla graph extract from a PBF, using the Valhalla
+  install already present on the runner. Outputs a single tile_extract tar.
+
+inputs:
+  pbf_path:
+    description: "Path to the OSM PBF to build the graph from"
+    required: true
+  tile_dir:
+    description: "Working directory to build raw tiles into before bundling"
+    required: false
+    default: "valhalla_tiles"
+
+outputs:
+  tile_extract:
+    description: "Absolute path to the built, uncompressed tile extract tar"
+    value: ${{ steps.extract.outputs.tile_extract }}
+
+runs:
+  using: composite
+  steps:
+    - name: Build config, admins, and tiles
+      shell: bash
+      run: |
+        mkdir -p "${{ inputs.tile_dir }}"
+        valhalla_build_config \
+          --mjolnir-tile-dir "${{ inputs.tile_dir }}" \
+          --mjolnir-admin "${{ inputs.tile_dir }}/admins.sqlite" \
+          --mjolnir-tile-extract "${{ inputs.tile_dir }}/tiles.tar" \
+          > /tmp/valhalla-build.json
+        valhalla_build_admins -c /tmp/valhalla-build.json "${{ inputs.pbf_path }}"
+        valhalla_build_tiles -c /tmp/valhalla-build.json "${{ inputs.pbf_path }}"
+
+    - name: Bundle tiles into a single extract
+      id: extract
+      shell: bash
+      run: |
+        valhalla_build_extract -c /tmp/valhalla-build.json -v
+        tile_count=$(find "${{ inputs.tile_dir }}" -name "*.gph" | wc -l)
+        echo "built $tile_count tile(s)"
+        test -f "${{ inputs.tile_dir }}/tiles.tar"
+        echo "tile_extract=$(pwd)/${{ inputs.tile_dir }}/tiles.tar" >> "$GITHUB_OUTPUT"

.github/actions/build-valhalla/action.yml

@@ -0,0 +1,68 @@
+name: Build Valhalla
+description: >
+  Builds Valhalla from source as a Python wheel and installs it into the
+  current job's environment.
+
+inputs:
+  valhalla_ref:
+    description: "Valhalla git ref to build (branch, tag, or commit SHA)"
+    required: true
+  python_version:
+    description: "Python version to build and install the wheel against"
+    required: false
+    default: "3.12"
+
+runs:
+  using: composite
+  steps:
+    - name: Set up Python
+      uses: actions/setup-python@v6
+      with:
+        python-version: ${{ inputs.python_version }}
+
+    - name: Sanitize ref for cache key
+      id: sanitize
+      shell: bash
+      run: echo "ref_slug=$(echo '${{ inputs.valhalla_ref }}' | tr '/' '-')" >> "$GITHUB_OUTPUT"
+
+    - name: Checkout Valhalla
+      uses: actions/checkout@v6
+      with:
+        repository: valhalla/valhalla
+        ref: ${{ inputs.valhalla_ref }}
+        submodules: recursive
+        path: valhalla-src
+
+    - name: Install system dependencies
+      shell: bash
+      run: bash valhalla-src/scripts/install-linux-deps.sh
+
+    - name: Restore ccache
+      uses: actions/cache/restore@v4
+      with:
+        path: ~/.cache/ccache
+        key: ccache-valhalla-${{ steps.sanitize.outputs.ref_slug }}
+        restore-keys: |
+          ccache-valhalla-master
+
+    # pyproject.toml sets Release/ENABLE_PYTHON_BINDINGS/ENABLE_TESTS defaults
+    - name: Build wheel
+      shell: bash
+      run: |
+        cd valhalla-src
+        pip wheel . --wheel-dir /tmp/valhalla-dist \
+          -Cbuild-dir=/tmp/valhalla-build \
+          -Ccmake.define.ENABLE_TOOLS=ON \
+          -Ccmake.define.ENABLE_SERVICES=OFF \
+          -Ccmake.define.ENABLE_CCACHE=ON
+
+    - name: Save ccache
+      if: always()
+      uses: actions/cache/save@v4
+      with:
+        path: ~/.cache/ccache
+        key: ccache-valhalla-${{ steps.sanitize.outputs.ref_slug }}
+
+    - name: Install wheel
+      shell: bash
+      run: pip install /tmp/valhalla-dist/*.whl

.github/workflows/routing-regression.yml

@@ -0,0 +1,109 @@
+name: Routing Regression
+
+on:
+  workflow_dispatch:
+    inputs:
+      valhalla_ref_old:
+        description: "Baseline Valhalla ref (the 'before')"
+        default: master
+        required: true
+      valhalla_ref_new:
+        description: "New Valhalla ref to test (the 'after' - branch, tag, or SHA)"
+        required: true
+
+# queue concurrent runs rather than cancel
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  regression:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - label: old
+            ref: ${{ inputs.valhalla_ref_old }}
+          - label: new
+            ref: ${{ inputs.valhalla_ref_new }}
+
+    steps:
+      - name: Checkout RAD
+        uses: actions/checkout@v6
+        with:
+          lfs: true
+
+      - name: Checkout RAD-data
+        uses: actions/checkout@v6
+        with:
+          repository: valhalla/RAD-data
+          path: RAD-data
+
+      - name: Build Valhalla at ${{ matrix.label }} ref
+        uses: ./.github/actions/build-valhalla
+        with:
+          valhalla_ref: ${{ matrix.ref }}
+          python_version: "3.12"
+
+      - name: Build tiles for ${{ matrix.label }} ref
+        id: tiles
+        uses: ./.github/actions/build-tiles
+        with:
+          pbf_path: data/liechtenstein_graph.osm.pbf
+
+      - name: Run route requests
+        run: |
+          python3 scripts/run_routes.py \
+            --tile-extract "${{ steps.tiles.outputs.tile_extract }}" \
+            --requests RAD-data/requests/requests.jsonl \
+            --output /tmp/responses-${{ matrix.label }}.jsonl
+
+      # responses are only needed for the current run's diff-and-store job, 7 days is generous
+      - name: Upload responses artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: responses-${{ matrix.label }}
+          path: /tmp/responses-${{ matrix.label }}.jsonl
+          retention-days: 7
+
+  diff-and-store:
+    runs-on: ubuntu-latest
+    needs: regression
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout RAD
+        uses: actions/checkout@v6
+
+      - name: Checkout RAD-data
+        uses: actions/checkout@v6
+        with:
+          repository: valhalla/RAD-data
+          path: RAD-data
+
+      - name: Download responses
+        uses: actions/download-artifact@v4
+        with:
+          pattern: responses-*
+          path: /tmp/responses
+          merge-multiple: false
+
+      # Debug step
+      - name: List downloaded artifacts
+        run: find /tmp/responses -type f
+
+      - name: Compute diff and push to RAD-data
+        run: |
+          python3 scripts/diff_responses.py \
+            --old /tmp/responses/responses-old/responses-old.jsonl \
+            --new /tmp/responses/responses-new/responses-new.jsonl \
+            --old-ref "${{ inputs.valhalla_ref_old }}" \
+            --new-ref "${{ inputs.valhalla_ref_new }}" \
+            --output RAD-data/diffs/${{ github.run_id }}.json
+          cd RAD-data
+          git config user.name  "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add diffs/${{ github.run_id }}.json
+          git commit -m "regression: ${{ inputs.valhalla_ref_old }} vs ${{ inputs.valhalla_ref_new }} (run ${{ github.run_id }})"
+          git push https://x-access-token:${{ secrets.RAD_DATA_TOKEN }}@github.com/valhalla/RAD-data.git

architecture.md

@@ -0,0 +1,118 @@
+# RAD — Routing Regression Pipeline
+
+```mermaid
+flowchart TD
+    TRIGGER(["`**workflow_dispatch**
+    valhalla_ref_old · valhalla_ref_new`"])
+
+    TRIGGER -->|matrix: label=old| OLD_JOB
+    TRIGGER -->|matrix: label=new| NEW_JOB
+
+    subgraph OLD_JOB ["old ref runner (ubuntu-latest)"]
+        direction TB
+        O1["① build-valhalla
+        composite action
+        ─────────────────
+        checkout valhalla at old ref
+        install-linux-deps.sh
+        restore ccache ← actions/cache
+        pip wheel . -Cbuild-dir=/tmp/valhalla-build
+        save ccache → actions/cache
+        pip install wheel"]
+
+        O2["② build-tiles
+        composite action
+        ─────────────────
+        valhalla_build_config
+        valhalla_build_admins
+        valhalla_build_tiles
+        valhalla_build_extract → tiles.tar"]
+
+        O3["③ run routes
+        ─────────────────
+        run_routes.py
+        pyvalhalla Actor in-process
+        → responses-old.jsonl"]
+
+        O4[/"④ upload artifact
+        responses-old.jsonl"/]
+
+        O1 --> O2 --> O3 --> O4
+    end
+
+    subgraph NEW_JOB ["new ref runner (ubuntu-latest)"]
+        direction TB
+        N1["① build-valhalla
+        composite action
+        ─────────────────
+        checkout valhalla at new ref
+        install-linux-deps.sh
+        restore ccache ← actions/cache
+        pip wheel . -Cbuild-dir=/tmp/valhalla-build
+        save ccache → actions/cache
+        pip install wheel"]
+
+        N2["② build-tiles
+        composite action
+        ─────────────────
+        valhalla_build_config
+        valhalla_build_admins
+        valhalla_build_tiles
+        valhalla_build_extract → tiles.tar"]
+
+        N3["③ run routes
+        ─────────────────
+        run_routes.py
+        pyvalhalla Actor in-process
+        → responses-new.jsonl"]
+
+        N4[/"④ upload artifact
+        responses-new.jsonl"/]
+
+        N1 --> N2 --> N3 --> N4
+    end
+
+    O4 --> DIFF
+    N4 --> DIFF
+
+    subgraph DIFF ["diff-and-store (needs: regression)"]
+        direction TB
+        D1["download both artifacts
+        ─────────────────
+        responses-old.jsonl
+        responses-new.jsonl"]
+
+        D2["diff_responses.py
+        ─────────────────
+        geometry delta · duration delta
+        instruction diff · severity score"]
+
+        D3["git commit → valhalla/RAD-data
+        ─────────────────
+        diffs/{run_id}.json
+        push via RAD_DATA_TOKEN"]
+
+        D1 --> D2 --> D3
+    end
+
+    CACHE[("actions/cache
+    ~/.cache/ccache
+    key: ccache-valhalla-{ref_slug}")]
+
+    RADDATA[("valhalla/RAD-data
+    diffs/{run_id}.json")]
+
+    O1 <-->|restore / save| CACHE
+    N1 <-->|restore / save| CACHE
+    D3 -->|git push| RADDATA
+```
+
+## Storage layout
+
+| Data | Where | Lifetime |
+|------|--------|----------|
+| ccache object files | GitHub `actions/cache` | until evicted (7-day LRU) |
+| pyvalhalla wheel (16MB) | `/tmp/valhalla-dist` on runner | single job |
+| graph tiles tar | `/tmp/valhalla_tiles` on runner | single job |
+| route responses | GHA artifact | 7 days |
+| diff results | `valhalla/RAD-data` git commit | permanent |