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: [labeled]
   workflow_dispatch:
 
 permissions:
@@ -17,6 +19,7 @@ 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.label.name, 'run benchmarks')
     steps:
       - name: Install Git
         run: |
@@ -46,9 +49,11 @@ jobs:
           java -jar libs/opentelemetry-sdk-trace-*-jmh.jar -rf json SpanBenchmark SpanPipelineBenchmark ExporterBenchmark
 
       - 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 +62,37 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           benchmark-data-dir-path: "benchmarks"
           auto-push: true
+
+      - name: Upload benchmark results (PR)
+        if: github.event_name == 'pull_request'
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: jmh-result.json
+          path: sdk/trace/build/jmh-result.json
+
+      - name: Comment benchmark results on PR
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
+        with:
+          script: |
+            const fs = require('fs');
+            const results = JSON.parse(fs.readFileSync('sdk/trace/build/jmh-result.json', 'utf8'));
+            
+            let comment = '## Benchmark Results\n\n';
+            comment += '| Benchmark | Score | Unit |\n';
+            comment += '|-----------|-------|------|\n';
+            
+            results.forEach(result => {
+              const score = result.primaryMetric.score.toFixed(2);
+              const unit = result.primaryMetric.scoreUnit;
+              comment += `| ${result.benchmark} | ${score} | ${unit} |\n`;
+            });
+            
+            comment += '\nFull results are available as an artifact named `jmh-result.json`';
+            
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: comment
+            });