repository: Add benchmark for FindLicensetoon-speedup-find-license

To get a sense of the performance of FindLicense, add this benchmark.

    goos: linux
    goarch: amd64
    pkg: gitlab.com/gitlab-org/gitaly/v15/internal/gitaly/service/repository
    cpu: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
    BenchmarkFindLicense
    BenchmarkFindLicense/read_object_cached=false
    BenchmarkFindLicense/read_object_cached=false/gitlab-org/gitlab.git
        license_test.go:380: git commands for loop: 6
        license_test.go:380: git commands for loop: 6
        license_test.go:380: git commands for loop: 6
    BenchmarkFindLicense/read_object_cached=false/gitlab-org/gitlab.git-8  20    50347475 ns/op
    BenchmarkFindLicense/read_object_cached=false/stress.git
        license_test.go:380: git commands for loop: 113
    BenchmarkFindLicense/read_object_cached=false/stress.git-8              1  1797435782 ns/op
    BenchmarkFindLicense/read_object_cached=true
    BenchmarkFindLicense/read_object_cached=true/gitlab-org/gitlab.git
        license_test.go:380: git commands for loop: 4
        license_test.go:380: git commands for loop: 3
        license_test.go:380: git commands for loop: 3
        license_test.go:380: git commands for loop: 3
    BenchmarkFindLicense/read_object_cached=true/gitlab-org/gitlab.git-8   48    23122846 ns/op
    BenchmarkFindLicense/read_object_cached=true/stress.git
        license_test.go:380: git commands for loop: 4
        license_test.go:380: git commands for loop: 3
    BenchmarkFindLicense/read_object_cached=true/stress.git-8               2   610536118 ns/op

This benchmark includes the number of git commands for each loop. It's
visible the benchmarks where the catfile cache is used a significant
lower number of git commands is spawn.

1 files changed, 119 insertions, 0 deletions

diff --git a/internal/gitaly/service/repository/license_test.go b/internal/gitaly/service/repository/license_test.go
index 2748b4bd2..cffc9db0b 100644
--- a/internal/gitaly/service/repository/license_test.go
+++ b/internal/gitaly/service/repository/license_test.go
@@ -7,15 +7,20 @@ import (
 	"os"
 	"testing"
 
+	"github.com/go-enry/go-license-detector/v4/licensedb"
 	"github.com/stretchr/testify/require"
+	"gitlab.com/gitlab-org/gitaly/v15/internal/git/catfile"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/gittest"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/gitaly/config"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/gitaly/rubyserver"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/metadata/featureflag"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/testhelper"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/testhelper/testcfg"
+	"gitlab.com/gitlab-org/gitaly/v15/internal/testhelper/testserver"
 	"gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb"
+	"gitlab.com/gitlab-org/labkit/correlation"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
 )
 
@@ -282,3 +287,117 @@ func TestFindLicense_validate(t *testing.T) {
 	msg := testhelper.GitalyOrPraefectMessage("empty Repository", "repo scoped: empty Repository")
 	testhelper.RequireGrpcError(t, status.Error(codes.InvalidArgument, msg), err)
 }
+
+func BenchmarkFindLicense(b *testing.B) {
+	cfg := testcfg.Build(b)
+	ctx := testhelper.Context(b)
+	ctx = featureflag.ContextWithFeatureFlag(ctx, featureflag.GoFindLicense, true)
+
+	gitCmdFactory := gittest.NewCountingCommandFactory(b, cfg)
+
+	client, serverSocketPath := runRepositoryService(
+		b,
+		cfg,
+		nil,
+		testserver.WithGitCommandFactory(gitCmdFactory),
+		testserver.WithDisablePraefect(),
+	)
+	cfg.SocketPath = serverSocketPath
+
+	// Warm up the license database
+	licensedb.Preload()
+
+	repoGitLab, _ := gittest.CreateRepository(b, ctx, cfg, gittest.CreateRepositoryConfig{
+		SkipCreationViaService: true,
+		Seed:                   "benchmark.git",
+	})
+
+	repoStress, repoStressPath := gittest.CreateRepository(b, ctx, cfg, gittest.CreateRepositoryConfig{
+		SkipCreationViaService: true,
+	})
+
+	// Based on https://github.com/go-enry/go-license-detector/blob/18a439e5437cd46905b074ac24c27cbb6cac4347/licensedb/internal/investigation.go#L28-L38
+	fileNames := []string{
+		"licence",
+		"lisence", //nolint:misspell
+		"lisense", //nolint:misspell
+		"license",
+		"licences",
+		"lisences",
+		"lisenses",
+		"licenses",
+		"legal",
+		"copyleft",
+		"copyright",
+		"copying",
+		"unlicense",
+		"gpl-v1",
+		"gpl-v2",
+		"gpl-v3",
+		"lgpl-v1",
+		"lgpl-v2",
+		"lgpl-v3",
+		"bsd",
+		"mit",
+		"apache",
+	}
+	fileExtensions := []string{
+		"",
+		".md",
+		".rst",
+		".html",
+		".txt",
+	}
+
+	treeEntries := make([]gittest.TreeEntry, 0, len(fileNames)*len(fileExtensions))
+
+	for _, name := range fileNames {
+		for _, ext := range fileExtensions {
+			treeEntries = append(treeEntries,
+				gittest.TreeEntry{
+					Mode:    "100644",
+					Path:    name + ext,
+					Content: mitLicense + "\n" + name, // grain of salt
+				})
+		}
+	}
+
+	gittest.WriteCommit(b, cfg, repoStressPath, gittest.WithBranch("main"),
+		gittest.WithTreeEntries(treeEntries...))
+	gittest.Exec(b, cfg, "-C", repoStressPath, "symbolic-ref", "HEAD", "refs/heads/main")
+
+	testhelper.NewFeatureSets(featureflag.ReadObjectCached).Bench(b, func(b *testing.B, ctx context.Context) {
+		ctx = featureflag.ContextWithFeatureFlag(ctx, featureflag.GoFindLicense, true)
+
+		ctx = correlation.ContextWithCorrelation(ctx, "1")
+		ctx = testhelper.MergeOutgoingMetadata(ctx,
+			metadata.Pairs(catfile.SessionIDField, "1"),
+		)
+
+		for _, tc := range []struct {
+			desc string
+			repo *gitalypb.Repository
+		}{
+			{
+				desc: "gitlab-org/gitlab.git",
+				repo: repoGitLab,
+			},
+			{
+				desc: "stress.git",
+				repo: repoStress,
+			},
+		} {
+			b.Run(tc.desc, func(b *testing.B) {
+				gitCmdFactory.ResetCount()
+
+				for i := 0; i < b.N; i++ {
+					resp, err := client.FindLicense(ctx, &gitalypb.FindLicenseRequest{Repository: tc.repo})
+					require.NoError(b, err)
+					require.Equal(b, "mit", resp.GetLicenseShortName())
+				}
+
+				b.Logf("git commands for loop: %d\n", gitCmdFactory.Count()/uint64(b.N))
+			})
+		}
+	})
+}