// Start calculating and reporting statistics on the repo and tiles.
//
// We presume the git.Update(true) is called somewhere else, usually this is done
// in the trace/db.Builder, so the repo is always as good as the loaded tiles.
func Start(nanoTileStore *db.Builder, git *gitinfo.GitInfo) {
	coverage := metrics.NewRegisteredGaugeFloat64("stats.tests.bench_runs_per_changelist", metrics.DefaultRegistry)
	skpLatency := metrics.NewRegisteredTimer("stats.skp.update_latency", metrics.DefaultRegistry)
	commits := metrics.NewRegisteredGauge("stats.commits.total", metrics.DefaultRegistry)

	go func() {
		for _ = range time.Tick(2 * time.Minute) {
			tile := nanoTileStore.GetTile()
			numCommits := tile.LastCommitIndex() + 1
			numTraces := len(tile.Traces)
			total := 0
			for _, tr := range tile.Traces {
				for i := 0; i < numCommits; i++ {
					if !tr.IsMissing(i) {
						total += 1
					}
				}
			}
			cov := float64(total) / float64(numCommits*numTraces)
			glog.Info("Coverage: ", cov)
			coverage.Update(cov)

			last, err := git.LastSkpCommit()
			if err != nil {
				glog.Warning("Failed to read last SKP commit: %s", err)
				continue
			}
			skpLatency.Update(time.Since(last))
			commits.Update(int64(git.NumCommits()))
		}
	}()
}

// findCommitsRecursive is a recursive function called by FindCommitsForBuild.
// It traces the history to find builds which were first included in the given
// build.
func findCommitsRecursive(commits map[string]bool, b *Build, hash string, repo *gitinfo.GitInfo, stealFrom int, stolen []string) (map[string]bool, int, []string, error) {
	// Shortcut for empty hashes. This can happen when a commit has no
	// parents (initial commit) or when a Build has no GotRevision.
	if hash == "" {
		return commits, stealFrom, stolen, nil
	}

	// Determine whether any build already includes this commit.
	n, err := GetBuildForCommit(b.Builder, b.Master, hash)
	if err != nil {
		return commits, stealFrom, stolen, fmt.Errorf("Could not find build for commit %s: %v", hash, err)
	}
	// If so, we have to make a decision.
	if n >= 0 {
		// If the build we found is the current build, keep going,
		// since we may have already ingested data for this build but still
		// need to find accurate revision data.
		if n != b.Number {
			// If this Build's GotRevision is already included in a different
			// Build, then we're "inserting" this one in between two already-ingested
			// Builds. In that case, this build is providing "better" information
			// on the already-claimed commits, so we steal them from the other Build.
			if hash == b.GotRevision {
				stealFrom = n
			}
			if stealFrom == n {
				stolen = append(stolen, hash)
			} else {
				return commits, stealFrom, stolen, nil
			}
		}
	}

	// Add the commit.
	commits[hash] = true

	// Recurse on the commit's parents.
	c, err := repo.Details(hash)
	if err != nil {
		// Special case. Commits can disappear from the repository
		// after they're picked up by the buildbots but before they're
		// ingested here. If we can't find a commit, log an error and
		// skip the commit.
		glog.Errorf("Failed to obtain details for %s: %v", hash, err)
		delete(commits, hash)
		return commits, stealFrom, stolen, nil
	}
	for _, p := range c.Parents {
		// If we've already seen this parent commit, don't revisit it.
		if _, ok := commits[p]; ok {
			continue
		}
		commits, stealFrom, stolen, err = findCommitsRecursive(commits, b, p, repo, stealFrom, stolen)
		if err != nil {
			return commits, stealFrom, stolen, err
		}
	}
	return commits, stealFrom, stolen, nil
}

// updateRepo syncs the given repo and returns a set of BuildCandidates for it.
func (q *BuildQueue) updateRepo(repoUrl string, repo *gitinfo.GitInfo, now time.Time) (map[string][]*BuildCandidate, error) {
	from := now.Add(-q.period)
	if q.period == PERIOD_FOREVER {
		from = time.Unix(0, 0)
	}
	recentCommits := repo.From(from)
	commitDetails := map[string]*gitinfo.LongCommit{}
	for _, c := range recentCommits {
		details, err := repo.Details(c)
		if err != nil {
			return nil, err
		}
		commitDetails[c] = details
	}

	// Get all builds associated with the recent commits.
	buildsByCommit, err := buildbot.GetBuildsForCommits(recentCommits, map[int]bool{})
	if err != nil {
		return nil, err
	}

	// Find the sets of all bots and masters, organize builds by
	// commit/builder and builder/number.
	masters := map[string]string{}
	builds := map[string]map[string]*buildbot.Build{}
	buildsByBuilderAndNum := map[string]map[int]*buildbot.Build{}
	for commit, buildsForCommit := range buildsByCommit {
		builds[commit] = map[string]*buildbot.Build{}
		for _, build := range buildsForCommit {
			if !util.In(build.Builder, q.botWhitelist) {
				continue
			}
			masters[build.Builder] = build.Master
			builds[commit][build.Builder] = build
			if _, ok := buildsByBuilderAndNum[build.Builder]; !ok {
				buildsByBuilderAndNum[build.Builder] = map[int]*buildbot.Build{}
			}
			buildsByBuilderAndNum[build.Builder][build.Number] = build
		}
	}
	allBots := make([]string, 0, len(masters))
	for builder, _ := range masters {
		allBots = append(allBots, builder)
	}

	// Find the current scores for each commit/builder pair.
	currentScores := map[string]map[string]float64{}
	for _, commit := range recentCommits {
		myBuilds, ok := builds[commit]
		if !ok {
			myBuilds = map[string]*buildbot.Build{}
		}
		currentScores[commit] = map[string]float64{}
		for _, builder := range allBots {
			currentScores[commit][builder] = scoreBuild(commitDetails[commit], myBuilds[builder], now, q.timeLambda)
		}
	}

	// For each commit/builder pair, determine the score increase obtained
	// by running a build at that commit.
	scoreIncrease := map[string]map[string]float64{}
	for _, commit := range recentCommits {
		scoreIncrease[commit] = map[string]float64{}
		for _, builder := range allBots {
			// Shortcut: Don't bisect builds with a huge number
			// of commits.  This saves lots of time and only affects
			// the first successful build for a bot.
			if _, ok := builds[commit][builder]; ok {
				if len(builds[commit][builder].Commits) > NO_BISECT_COMMIT_LIMIT {
					glog.Warningf("Skipping %s on %s; previous build has too many commits.", commit[0:7], builder)
					scoreIncrease[commit][builder] = 0.0
					continue
				}
			}

			newScores := map[string]float64{}
			// Pretend to create a new Build at the given commit.
			newBuild := buildbot.Build{
				Builder:     builder,
				Master:      masters[builder],
				Number:      math.MaxInt32,
				GotRevision: commit,
				Repository:  repoUrl,
			}
			commits, stealFrom, stolen, err := buildbot.FindCommitsForBuild(&newBuild, q.repos)
			if err != nil {
				return nil, err
			}
			// Re-score all commits in the new build.
			newBuild.Commits = commits
			for _, c := range commits {
				if _, ok := currentScores[c]; !ok {
					// If this build has commits which are outside of our window,
					// insert them into currentScores to account for them.
					score := scoreBuild(commitDetails[commit], builds[commit][builder], now, q.timeLambda)
					currentScores[c] = map[string]float64{
						builder: score,
					}
				}
//.........这里部分代码省略.........