Faster commit lookup (go-gitea#91)

* Faster commit lookup

* Fix copy/rename bug

* Comment

* Use defer

commit_info.go

@@ -0,0 +1,307 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package git
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os/exec"
+	"path"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	// parameters for searching for commit infos. If the untargeted search has
+	// not found any entries in the past 5 commits, and 12 or fewer entries
+	// remain, then we'll just let the targeted-searching threads finish off,
+	// and stop the untargeted search to not interfere.
+	deferToTargetedSearchColdStreak          = 5
+	deferToTargetedSearchNumRemainingEntries = 12
+)
+
+// getCommitsInfoState shared state while getting commit info for entries
+type getCommitsInfoState struct {
+	lock sync.Mutex
+	/* read-only fields, can be read without the mutex */
+	// entries and entryPaths are read-only after initialization, so they can
+	// safely be read without the mutex
+	entries []*TreeEntry
+	// set of filepaths to get info for
+	entryPaths map[string]struct{}
+	treePath   string
+	headCommit *Commit
+
+	/* mutable fields, must hold mutex to read or write */
+	// map from filepath to commit
+	commits map[string]*Commit
+	// set of filepaths that have been or are being searched for in a target search
+	targetedPaths map[string]struct{}
+}
+
+func (state *getCommitsInfoState) numRemainingEntries() int {
+	state.lock.Lock()
+	defer state.lock.Unlock()
+	return len(state.entries) - len(state.commits)
+}
+
+// getTargetEntryPath Returns the next path for a targeted-searching thread to
+// search for, or returns the empty string if nothing left to search for
+func (state *getCommitsInfoState) getTargetedEntryPath() string {
+	var targetedEntryPath string
+	state.lock.Lock()
+	defer state.lock.Unlock()
+	for _, entry := range state.entries {
+		entryPath := path.Join(state.treePath, entry.Name())
+		if _, ok := state.commits[entryPath]; ok {
+			continue
+		} else if _, ok = state.targetedPaths[entryPath]; ok {
+			continue
+		}
+		targetedEntryPath = entryPath
+		state.targetedPaths[entryPath] = struct{}{}
+		break
+	}
+	return targetedEntryPath
+}
+
+// repeatedly perform targeted searches for unpopulated entries
+func targetedSearch(state *getCommitsInfoState, done chan error) {
+	for {
+		entryPath := state.getTargetedEntryPath()
+		if len(entryPath) == 0 {
+			done <- nil
+			return
+		}
+		command := NewCommand("rev-list", "-1", "HEAD", "--", entryPath)
+		output, err := command.RunInDir(state.headCommit.repo.Path)
+		if err != nil {
+			done <- err
+			return
+		}
+		id, err := NewIDFromString(strings.TrimSpace(output))
+		if err != nil {
+			done <- err
+			return
+		}
+		commit, err := state.headCommit.repo.getCommit(id)
+		if err != nil {
+			done <- err
+			return
+		}
+		state.update(entryPath, commit)
+	}
+}
+
+func initGetCommitInfoState(entries Entries, headCommit *Commit, treePath string) *getCommitsInfoState {
+	entryPaths := make(map[string]struct{}, len(entries))
+	for _, entry := range entries {
+		entryPaths[path.Join(treePath, entry.Name())] = struct{}{}
+	}
+	if treePath = path.Clean(treePath); treePath == "." {
+		treePath = ""
+	}
+	return &getCommitsInfoState{
+		entries:       entries,
+		entryPaths:    entryPaths,
+		commits:       make(map[string]*Commit, len(entries)),
+		targetedPaths: make(map[string]struct{}, len(entries)),
+		treePath:      treePath,
+		headCommit:    headCommit,
+	}
+}
+
+// GetCommitsInfo gets information of all commits that are corresponding to these entries
+func (tes Entries) GetCommitsInfo(commit *Commit, treePath string) ([][]interface{}, error) {
+	state := initGetCommitInfoState(tes, commit, treePath)
+	if err := getCommitsInfo(state); err != nil {
+		return nil, err
+	}
+	if len(state.commits) < len(state.entryPaths) {
+		return nil, fmt.Errorf("could not find commits for all entries")
+	}
+
+	commitsInfo := make([][]interface{}, len(tes))
+	for i, entry := range tes {
+		commit, ok := state.commits[path.Join(treePath, entry.Name())]
+		if !ok {
+			return nil, fmt.Errorf("could not find commit for %s", entry.Name())
+		}
+		switch entry.Type {
+		case ObjectCommit:
+			subModuleURL := ""
+			if subModule, err := state.headCommit.GetSubModule(entry.Name()); err != nil {
+				return nil, err
+			} else if subModule != nil {
+				subModuleURL = subModule.URL
+			}
+			subModuleFile := NewSubModuleFile(commit, subModuleURL, entry.ID.String())
+			commitsInfo[i] = []interface{}{entry, subModuleFile}
+		default:
+			commitsInfo[i] = []interface{}{entry, commit}
+		}
+	}
+	return commitsInfo, nil
+}
+
+func (state *getCommitsInfoState) cleanEntryPath(rawEntryPath string) (string, error) {
+	if rawEntryPath[0] == '"' {
+		var err error
+		rawEntryPath, err = strconv.Unquote(rawEntryPath)
+		if err != nil {
+			return rawEntryPath, err
+		}
+	}
+	var entryNameStartIndex int
+	if len(state.treePath) > 0 {
+		entryNameStartIndex = len(state.treePath) + 1
+	}
+
+	if index := strings.IndexByte(rawEntryPath[entryNameStartIndex:], '/'); index >= 0 {
+		return rawEntryPath[:entryNameStartIndex+index], nil
+	}
+	return rawEntryPath, nil
+}
+
+// update report that the given path was last modified by the given commit.
+// Returns whether state.commits was updated
+func (state *getCommitsInfoState) update(entryPath string, commit *Commit) bool {
+	if _, ok := state.entryPaths[entryPath]; !ok {
+		return false
+	}
+
+	var updated bool
+	state.lock.Lock()
+	defer state.lock.Unlock()
+	if _, ok := state.commits[entryPath]; !ok {
+		state.commits[entryPath] = commit
+		updated = true
+	}
+	return updated
+}
+
+const getCommitsInfoPretty = "--pretty=format:%H %ct %s"
+
+func getCommitsInfo(state *getCommitsInfoState) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Minute)
+	defer cancel()
+
+	args := []string{"log", getCommitsInfoPretty, "--name-status", "-c"}
+	if len(state.treePath) > 0 {
+		args = append(args, "--", state.treePath)
+	}
+	cmd := exec.CommandContext(ctx, "git", args...)
+	cmd.Dir = state.headCommit.repo.Path
+
+	readCloser, err := cmd.StdoutPipe()
+	if err != nil {
+		return err
+	}
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	numThreads := runtime.NumCPU()
+	done := make(chan error, numThreads)
+	for i := 0; i < numThreads; i++ {
+		go targetedSearch(state, done)
+	}
+
+	scanner := bufio.NewScanner(readCloser)
+	err = state.processGitLogOutput(scanner)
+	for i := 0; i < numThreads; i++ {
+		doneErr := <-done
+		if doneErr != nil && err == nil {
+			err = doneErr
+		}
+	}
+	return err
+}
+
+func (state *getCommitsInfoState) processGitLogOutput(scanner *bufio.Scanner) error {
+	// keep a local cache of seen paths to avoid acquiring a lock for paths
+	// we've already seen
+	seenPaths := make(map[string]struct{}, len(state.entryPaths))
+	// number of consecutive commits without any finds
+	coldStreak := 0
+	var commit *Commit
+	var err error
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) == 0 { // in-between commits
+			numRemainingEntries := state.numRemainingEntries()
+			if numRemainingEntries == 0 {
+				break
+			}
+			if coldStreak >= deferToTargetedSearchColdStreak &&
+				numRemainingEntries <= deferToTargetedSearchNumRemainingEntries {
+				// stop this untargeted search, and let the targeted-search threads
+				// finish the work
+				break
+			}
+			continue
+		}
+		if line[0] >= 'A' && line[0] <= 'X' { // a file was changed by the current commit
+			// look for the last tab, since for copies (C) and renames (R) two
+			// filenames are printed: src, then dest
+			tabIndex := strings.LastIndexByte(line, '\t')
+			if tabIndex < 1 {
+				return fmt.Errorf("misformatted line: %s", line)
+			}
+			entryPath, err := state.cleanEntryPath(line[tabIndex+1:])
+			if err != nil {
+				return err
+			}
+			if _, ok := seenPaths[entryPath]; !ok {
+				if state.update(entryPath, commit) {
+					coldStreak = 0
+				}
+				seenPaths[entryPath] = struct{}{}
+			}
+			continue
+		}
+
+		// a new commit
+		commit, err = parseCommitInfo(line)
+		if err != nil {
+			return err
+		}
+		coldStreak++
+	}
+	return scanner.Err()
+}
+
+// parseCommitInfo parse a commit from a line of `git log` output. Expects the
+// line to be formatted according to getCommitsInfoPretty.
+func parseCommitInfo(line string) (*Commit, error) {
+	if len(line) < 43 {
+		return nil, fmt.Errorf("invalid git output: %s", line)
+	}
+	ref, err := NewIDFromString(line[:40])
+	if err != nil {
+		return nil, err
+	}
+	spaceIndex := strings.IndexByte(line[41:], ' ')
+	if spaceIndex < 0 {
+		return nil, fmt.Errorf("invalid git output: %s", line)
+	}
+	unixSeconds, err := strconv.Atoi(line[41 : 41+spaceIndex])
+	if err != nil {
+		return nil, err
+	}
+	message := line[spaceIndex+42:]
+	return &Commit{
+		ID:            ref,
+		CommitMessage: message,
+		Committer: &Signature{
+			When: time.Unix(int64(unixSeconds), 0),
+		},
+	}, nil
+}

commit_info_test.go

@@ -0,0 +1,59 @@
+package git
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+const benchmarkReposDir = "benchmark/repos/"
+
+func setupGitRepo(url string, name string) (string, error) {
+	repoDir := filepath.Join(benchmarkReposDir, name)
+	if _, err := os.Stat(repoDir); err == nil {
+		return repoDir, nil
+	}
+	return repoDir, Clone(url, repoDir, CloneRepoOptions{
+		Mirror:  false,
+		Bare:    false,
+		Quiet:   true,
+		Timeout: 5 * time.Minute,
+	})
+}
+
+func BenchmarkEntries_GetCommitsInfo(b *testing.B) {
+	benchmarks := []struct {
+		url  string
+		name string
+	}{
+		{url: "https://github.com/go-gitea/gitea.git", name: "gitea"},
+		{url: "https://github.com/ethantkoenig/manyfiles.git", name: "manyfiles"},
+		{url: "https://github.com/moby/moby.git", name: "moby"},
+		{url: "https://github.com/golang/go.git", name: "go"},
+		{url: "https://github.com/torvalds/linux.git", name: "linux"},
+	}
+	for _, benchmark := range benchmarks {
+		var commit *Commit
+		var entries Entries
+		if repoPath, err := setupGitRepo(benchmark.url, benchmark.name); err != nil {
+			b.Fatal(err)
+		} else if repo, err := OpenRepository(repoPath); err != nil {
+			b.Fatal(err)
+		} else if commit, err = repo.GetBranchCommit("master"); err != nil {
+			b.Fatal(err)
+		} else if entries, err = commit.Tree.ListEntries(); err != nil {
+			b.Fatal(err)
+		}
+		entries.Sort()
+		b.ResetTimer()
+		b.Run(benchmark.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				_, err := entries.GetCommitsInfo(commit, "")
+				if err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}