.github/workflows/benchmark.yml

name: Benchmark
on:
  push:
    branches:
      - main
    paths:
      - '**/*.go'
      - '**/go.mod'
      - '**/go.sum'
      - 'Makefile'
      - '.github/workflows/benchmark.yml'
  schedule:
    - cron: '0 8 * * 0'
      timezone: America/Los_Angeles
  workflow_dispatch:
    inputs:
      full:
        description: "Run benchmarks for every module, ignoring the affected-module diff."
        type: boolean
        default: false

# Declare default permissions as read only.
permissions:
  contents: read

env:
  DEFAULT_GO_VERSION: "~1.27.0"
jobs:
  # Related issue: https://github.com/CodSpeedHQ/codspeed-go/issues/51
  sharding-benchmark:
    name: Sharding benchmarks
    runs-on: ubuntu-latest
    outputs:
      shards: ${{ steps.sharding.outputs.shards }}
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          persist-credentials: false
          # Need history so the affected-module detector can diff
          # against the prior commit.
          fetch-depth: 0
      - uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
        with:
          go-version: ${{ env.DEFAULT_GO_VERSION }}
          check-latest: true
          cache-dependency-path: "**/go.sum"
      - id: sharding
        env:
          # We want to diff HEAD against whatever "before this change"
          # means for the current event.
          #
          # For a PR, that's the commit on main the PR branched from --
          # we want every commit in the PR, not just the latest push.
          # (Tempting to use github.event.before here, but on PRs it's
          # the previous tip of the PR branch, so it'd miss earlier
          # commits in the same PR.)
          #
          # For a push to main, it's the commit that was at the tip
          # before this push -- exactly the new work this push brings.
          #
          # For a manual workflow_dispatch run, neither field is set,
          # and the Makefile's default base ref kicks in.
          BASE_REF: ${{ github.event.pull_request.base.sha || github.event.before || 'origin/main' }}
          ARGS: ${{ (github.event_name == 'schedule' || inputs.full) && '-all' || '' }}
        run: |
          shards=$(make print-affected-benchmarks)
          echo "shards=${shards}" >> "$GITHUB_OUTPUT"

  benchmark:
    needs: sharding-benchmark
    # Skip the matrix entirely when nothing benchmark-relevant changed.
    if: needs.sharding-benchmark.outputs.shards != '[]'
    permissions:
      contents: write # required for pushing to gh-pages branch
    name: Benchmarks
    runs-on: oracle-bare-metal-64cpu-1024gb-x86-64-ubuntu-24
    container:
      image: ubuntu:26.04@sha256:157dc3d6e4a3e4f2c68d12df9df9ed6e808b59af6d4c3757b432b4f519916725
      # CodSpeed's profiling feature needs elevated permissions.
      options: --cap-add=PERFMON
    strategy:
      matrix:
        shard: ${{ fromJson(needs.sharding-benchmark.outputs.shards) }}
    steps:
      # The benchmark container does not have the build toolchain preinstalled.
      - name: Install prerequisites
        run: |
          apt-get update
          apt-get install -y make build-essential git ca-certificates curl
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          persist-credentials: false
      # This makes CodSpeed running inside the container use git correctly.
      - name: Mark workspace as a safe Git directory
        run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
      - uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
        with:
          go-version: ${{ env.DEFAULT_GO_VERSION }}
          check-latest: true
          # Disable setup-go's GOMODCACHE/GOCACHE caching on the bare-metal
          # runner. The runner is persistent, so ~/go/pkg/mod and
          # ~/.cache/go-build already survive between jobs locally. The
          # Actions cache for this key reaches multiple GB across the matrix,
          # which makes every shard pay ~1-2 min on either the restore
          # (download + tar -xf) or the post-step save (tar + upload), with
          # no benefit over the on-disk caches.
          cache: false
      - name: Run the benchmarks
        env:
          # Job containers do not run systemd. Without this override,
          # CodSpeed tries to start the benchmark using systemd-run.
          CODSPEED_ISOLATION: "false"
        uses: CodSpeedHQ/action@af75f77f17a054769abefaa42fe8dc2975469b5f # v5.6.3
        with:
          mode: walltime
          allow-empty: true
          # CodSpeed runs extremely slow when there are 128 processes involved, which is the number
          # of CPUs on the bare metal machine. Limiting the number of processes to 4 helps mitigate this. 4 also matches the number of CPUs on GitHub runners.
          run: GOMAXPROCS=4 make benchmark/${{matrix.shard}}