chore(ci): Build modified backends on PR

Signed-off-by: Richard Palethorpe <[email protected]>

Author: richiejp

.github/workflows/backend_build.yml

@@ -55,13 +55,13 @@ on:
         type: string
     secrets:
       dockerUsername:
-        required: true
+        required: false
       dockerPassword:
-        required: true
+        required: false
       quayUsername:
-        required: true
+        required: false
       quayPassword:
-        required: true
+        required: false
 
 jobs:
   backend-build:
@@ -238,4 +238,4 @@ jobs:
 
       - name: job summary
         run: |
-          echo "Built image: ${{ steps.meta.outputs.labels }}" >> $GITHUB_STEP_SUMMARY 
+          echo "Built image: ${{ steps.meta.outputs.labels }}" >> $GITHUB_STEP_SUMMARY

.github/workflows/backend_pr.yml

@@ -0,0 +1,53 @@
+name: 'build backend container images (PR-filtered)'
+
+on:
+  pull_request:
+
+concurrency:
+  group: ci-backends-pr-${{ github.head_ref || github.ref }}-${{ github.repository }}
+  cancel-in-progress: true
+
+jobs:
+  generate-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+
+      - name: Install dependencies
+        run: |
+          bun add js-yaml
+          bun add @octokit/core
+
+      # filters the matrix in backend.yml
+      - name: Filter matrix for changed backends
+        id: set-matrix
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_EVENT_PATH: ${{ github.event_path }}
+        run: bun run scripts/changed-backends.js
+
+  backend-jobs:
+    needs: generate-matrix
+    uses: ./.github/workflows/backend_build.yml
+    with:
+      tag-latest: ${{ matrix.tag-latest }}
+      tag-suffix: ${{ matrix.tag-suffix }}
+      build-type: ${{ matrix.build-type }}
+      cuda-major-version: ${{ matrix.cuda-major-version }}
+      cuda-minor-version: ${{ matrix.cuda-minor-version }}
+      platforms: ${{ matrix.platforms }}
+      runs-on: ${{ matrix.runs-on }}
+      base-image: ${{ matrix.base-image }}
+      backend: ${{ matrix.backend }}
+      dockerfile: ${{ matrix.dockerfile }}
+      skip-drivers: ${{ matrix.skip-drivers }}
+      context: ${{ matrix.context }}
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.generate-matrix.outputs.matrix) }}

scripts/changed-backends.js

@@ -0,0 +1,73 @@
+import fs from "fs";
+import yaml from "js-yaml";
+import { Octokit } from "@octokit/core";
+
+// Load backend.yml and parse matrix.include
+const backendYml = yaml.load(fs.readFileSync(".github/workflows/backend.yml", "utf8"));
+const jobs = backendYml.jobs;
+const backendJob = jobs["backend-jobs"];
+const strategy = backendJob.strategy;
+const matrix = strategy.matrix;
+const includes = matrix.include;
+
+// Set up Octokit for PR changed files
+const token = process.env.GITHUB_TOKEN;
+const octokit = new Octokit({ auth: token });
+
+const eventPath = process.env.GITHUB_EVENT_PATH;
+const event = JSON.parse(fs.readFileSync(eventPath, "utf8"));
+
+let prNumber, repo, owner;
+if (event.pull_request) {
+  prNumber = event.pull_request.number;
+  repo = event.repository.name;
+  owner = event.repository.owner.login;
+} else {
+  throw new Error("This workflow must be triggered by a pull_request event.");
+}
+
+async function getChangedFiles() {
+  let files = [];
+  let page = 1;
+  while (true) {
+    const res = await octokit.request('GET /repos/{owner}/{repo}/pulls/{pull_number}/files', {
+      owner,
+      repo,
+      pull_number: prNumber,
+      per_page: 100,
+      page
+    });
+    files = files.concat(res.data.map(f => f.filename));
+    if (res.data.length < 100) break;
+    page++;
+  }
+  return files;
+}
+
+// Infer backend path
+function inferBackendPath(item) {
+  if (item.dockerfile === "Dockerfile.python") {
+    return `backend/python/${item.backend}`;
+  }
+  if (item.dockerfile === "Dockerfile.golang") {
+    return `backend/go/${item.backend}`;
+  }
+  if (item.dockerfile === "Dockerfile.llama-cpp") {
+    return `backend/cpp/llama-cpp`;
+  }
+  return null;
+}
+
+(async () => {
+  const changedFiles = await getChangedFiles();
+
+  const filtered = includes.filter(item => {
+    const backendPath = inferBackendPath(item);
+    if (!backendPath) return false;
+    return changedFiles.some(file => file.startsWith(backendPath));
+  });
+
+  // If no backends changed, fall back to an empty matrix to avoid workflow failure
+  const outputMatrix = filtered.length > 0 ? { include: filtered } : { include: [] };
+  fs.appendFileSync(process.env.GITHUB_OUTPUT, `matrix=${JSON.stringify(outputMatrix)}\n`);
+})();