pr-benchmarks.yml

---
name: PR Benchmarks

on:
  pull_request:
    types:
      - labeled

permissions: {}

concurrency:
  group: pr-benchmarks-${{ github.event.pull_request.number }}

defaults:
  run:
    shell: bash

jobs:
  benchmark:
    if: github.event.label.name == 'benchmark'
    runs-on: ubuntu-24.04
    strategy:
      fail-fast: false
      matrix:
        include:
          - topic: counter
            pattern: CounterBenchmark
          - topic: histogram
            pattern: HistogramBenchmark
          - topic: exposition
            pattern: HistogramTextFormatBenchmark|TextFormatUtilBenchmark
    permissions:
      contents: read # checkout only
    env:
      HEAD_SHA: ${{ github.event.pull_request.head.sha }}
      PR_NUMBER: ${{ github.event.pull_request.number }}
      JMH_PATTERN: ${{ matrix.pattern }}
    steps:
      - name: Checkout PR base
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          repository: ${{ github.repository }}
          ref: ${{ github.event.pull_request.base.sha }}
          persist-credentials: false
          fetch-depth: 0

      - name: Setup mise
        uses: jdx/mise-action@dad1bfd3df957f44999b559dd69dc1671cb4e9ea # v4.2.1
        with:
          version: v2026.7.5
          sha256: 5f7ab76afdf0780d12edeaa67e908094e9ccf7924cfe203e415c1cfb87bbf778

      - name: Cache local Maven repository
        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
        with:
          path: ~/.m2/repository
          key: ${{ runner.os }}-pr-bench-maven-${{ matrix.topic }}-${{ env.HEAD_SHA }}
          restore-keys: |
            ${{ runner.os }}-pr-bench-maven-${{ matrix.topic }}-
            ${{ runner.os }}-pr-bench-maven-
            ${{ runner.os }}-maven-

      - name: Capture runner info
        run: |
          python3 ./.mise/tasks/generate_benchmark_summary.py \
            --write-system-info /tmp/runner-info.json

      - name: Run base ${{ matrix.topic }} benchmarks
        run: mise run benchmark:ci-json
        env:
          JMH_ARGS: -f 3 -wi 3 -i 5 ${{ env.JMH_PATTERN }}

      - name: Save base ${{ matrix.topic }} results
        run: mv benchmark-results.json /tmp/base-results.json

      - name: Checkout PR head
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          repository: ${{ github.event.pull_request.head.repo.full_name }}
          ref: ${{ github.event.pull_request.head.sha }}
          persist-credentials: false
          fetch-depth: 0

      - name: Run head ${{ matrix.topic }} benchmarks
        run: mise run benchmark:ci-json
        env:
          JMH_ARGS: -f 3 -wi 3 -i 5 ${{ env.JMH_PATTERN }}

      - name: Save head ${{ matrix.topic }} results
        run: mv benchmark-results.json /tmp/head-results.json

      - name: Upload ${{ matrix.topic }} benchmark results
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
        with:
          name: pr-benchmark-topic-${{ matrix.topic }}-${{ env.PR_NUMBER }}-${{ env.HEAD_SHA }}
          path: |
            /tmp/base-results.json
            /tmp/head-results.json
            /tmp/runner-info.json
          retention-days: 5

  summarize:
    if: github.event.label.name == 'benchmark'
    runs-on: ubuntu-24.04
    needs: benchmark
    permissions:
      contents: read # checkout only
    env:
      HEAD_SHA: ${{ github.event.pull_request.head.sha }}
      PR_NUMBER: ${{ github.event.pull_request.number }}
    steps:
      - name: Checkout PR head
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          repository: ${{ github.event.pull_request.head.repo.full_name }}
          ref: ${{ github.event.pull_request.head.sha }}
          persist-credentials: false
          fetch-depth: 0

      - name: Download topic benchmark results
        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
        with:
          pattern: pr-benchmark-topic-*-${{ env.PR_NUMBER }}-${{ env.HEAD_SHA }}
          path: /tmp/topic-benchmark-results

      - name: Merge topic benchmark results
        run: |
          python3 - <<'PY'
          import json
          from pathlib import Path

          root = Path('/tmp/topic-benchmark-results')
          for name in ('base', 'head'):
              files = sorted(root.glob(f'*/{name}-results.json'))
              if not files:
                  raise SystemExit(f'No {name} benchmark result files found')
              merged = []
              for file in files:
                  with open(file, 'r') as f:
                      merged.extend(json.load(f))
              with open(f'/tmp/{name}-benchmark-results.json', 'w') as f:
                  json.dump(merged, f)
                  f.write('\n')
          PY

      - name: Generate benchmark summary
        run: |
          python3 ./.mise/tasks/generate_benchmark_summary.py \
            --input /tmp/head-benchmark-results.json \
            --baseline /tmp/base-benchmark-results.json \
            --output-dir benchmark-results \
            --commit-sha "${{ github.event.pull_request.head.sha }}" \
            --baseline-sha "${{ github.event.pull_request.base.sha }}" \
            --comparison-note \
              "Base and head are compared on the same runner within each topic."
        env:
          GITHUB_REPOSITORY: ${{ github.event.pull_request.head.repo.full_name }}
          GITHUB_BASE_REPOSITORY: ${{ github.repository }}

      - name: Prepare PR comment summary
        run: |
          cp benchmark-results/README.md pr-benchmark-comment.md

      - name: Upload PR benchmark results
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
        with:
          name: pr-benchmark-results-pr-${{ env.PR_NUMBER }}-${{ env.HEAD_SHA }}
          path: benchmark-results
          retention-days: 5

      - name: Upload PR benchmark comment
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
        with:
          name: pr-benchmark-comment-pr-${{ env.PR_NUMBER }}-${{ env.HEAD_SHA }}
          path: pr-benchmark-comment.md
          retention-days: 5