Add option to run benchmarks on PRs

Author: trask

.github/workflows/benchmark.yml

@@ -3,6 +3,8 @@ name: Benchmark Main
 on:
   push:
     branches: [ main ]
+  pull_request:
+    types: [opened, synchronize, reopened, labeled]
   workflow_dispatch:
 
 permissions:
@@ -17,6 +19,9 @@ jobs:
     container:
       image: ubuntu:24.04@sha256:353675e2a41babd526e2b837d7ec780c2a05bca0164f7ea5dbbd433d21d166fc
     timeout-minutes: 20 # since there is only a single bare metal runner across all repos
+    if: github.event_name != 'pull_request' || contains(github.event.pull_request.labels.*.name, 'run benchmarks')
+    env:
+      BENCHMARK_CLASSES: SpanBenchmark SpanPipelineBenchmark ExporterBenchmark
     steps:
       - name: Install Git
         run: |
@@ -37,18 +42,32 @@ jobs:
 
       - name: Set up gradle
         uses: gradle/actions/setup-gradle@ed408507eac070d1f99cc633dbcf757c94c7933a # v4.4.3
-      - name: Run jmh
-        run: ./gradlew jmhJar
 
       - name: Run Benchmark
         run: |
+          ./gradlew jmhJar
           cd sdk/trace/build
-          java -jar libs/opentelemetry-sdk-trace-*-jmh.jar -rf json SpanBenchmark SpanPipelineBenchmark ExporterBenchmark
+          java -jar libs/opentelemetry-sdk-trace-*-jmh.jar -rf json ${{ env.BENCHMARK_CLASSES }}
+
+      - name: Run Benchmark on main branch
+        if: github.event_name == 'pull_request'
+        run: |
+          # Save PR benchmark results so not overwritten
+          mv sdk/trace/build/jmh-result.json sdk/trace/build/jmh-result-pr.json
+          git checkout origin/main
+          ./gradlew jmhJar
+          cd sdk/trace/build
+          java -jar libs/opentelemetry-sdk-trace-*-jmh.jar -rf json ${{ env.BENCHMARK_CLASSES }}
+          # Rename main results and restore PR results
+          mv jmh-result.json jmh-result-main.json
+          mv jmh-result-pr.json jmh-result.json
 
       - name: Use CLA approved github bot
+        if: github.event_name != 'pull_request'
         run: .github/scripts/use-cla-approved-github-bot.sh
 
       - name: Store benchmark results
+        if: github.event_name != 'pull_request'
         uses: benchmark-action/github-action-benchmark@4bdcce38c94cec68da58d012ac24b7b1155efe8b # v1.20.7
         with:
           tool: 'jmh'
@@ -57,3 +76,12 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           benchmark-data-dir-path: "benchmarks"
           auto-push: true
+
+      - name: Upload benchmark results
+        if: github.event_name == 'pull_request'
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: benchmark-results
+          path: |
+            sdk/trace/build/jmh-result.json
+            sdk/trace/build/jmh-result-main.json