Improve the efficency of crawling github

Make sure a github file is crawled once

api/internal/crawl/crawler/crawler.go

@@ -29,7 +29,7 @@ type Crawler interface {
 	// Crawl returns when it is done processing. This method does not take
 	// ownership of the channel. The channel is write only, and it
 	// designates where the crawler should forward the documents.
-	Crawl(ctx context.Context, output chan<- CrawledDocument) error
+	Crawl(ctx context.Context, output chan<- CrawledDocument, seen map[string]struct{}) error
 
 	// Get the document data given the FilePath, Repo, and Ref/Tag/Branch.
 	FetchDocument(context.Context, *doc.Document) error
@@ -231,7 +231,7 @@ func CrawlFromSeed(ctx context.Context, seed CrawlSeed, crawlers []Crawler,
 // from the seed will be processed before any other documents from the
 // crawlers.
 func CrawlGithubRunner(ctx context.Context, output chan<- CrawledDocument,
-	crawlers []Crawler) []error {
+	crawlers []Crawler, seen map[string]struct{}) []error {
 
 	errs := make([]error, len(crawlers))
 	wg := sync.WaitGroup{}
@@ -265,7 +265,7 @@ func CrawlGithubRunner(ctx context.Context, output chan<- CrawledDocument,
 				}
 			}()
 			defer close(docs)
-			errs[idx] = crawler.Crawl(ctx, docs)
+			errs[idx] = crawler.Crawl(ctx, docs, seen)
 		}(i, crawler, docs) // Copies the index and the crawler
 	}
 
@@ -306,7 +306,7 @@ func CrawlGithub(ctx context.Context, crawlers []Crawler, conv Converter,
 	}()
 
 	logger.Println("processing the documents found from crawling github")
-	if errs := CrawlGithubRunner(ctx, ch, crawlers); errs != nil {
+	if errs := CrawlGithubRunner(ctx, ch, crawlers, seen); errs != nil {
 		for _, err := range errs {
 			logIfErr(err)
 		}

api/internal/crawl/crawler/crawler_test.go

@@ -75,7 +75,7 @@ func newCrawler(matchPrefix string, err error,
 
 // Crawl implements the Crawler interface for testing.
 func (c testCrawler) Crawl(_ context.Context,
-	output chan<- CrawledDocument) error {
+	output chan<- CrawledDocument, _ map[string]struct{}) error {
 
 	for i, d := range c.docs {
 		isResource := true
@@ -181,8 +181,9 @@ func TestCrawlGithubRunner(t *testing.T) {
 			defer close(output)
 			defer wg.Done()
 
+			seen := map[string]struct{}{}
 			errs := CrawlGithubRunner(context.Background(),
-				output, test.tc)
+				output, test.tc, seen)
 
 			// Check that errors are returned as they should be.
 			if !reflect.DeepEqual(errs, test.errs) {

api/internal/crawl/crawler/github/crawler.go

@@ -30,6 +30,8 @@ var logger = log.New(os.Stdout, "Github Crawler: ",
 type githubCrawler struct {
 	client GhClient
 	query  Query
+	// branchMap maps github repositories to their default branches
+	branchMap map[string]string
 }
 
 type GhClient struct {
@@ -52,12 +54,21 @@ func NewCrawler(accessToken string, retryCount uint64, client *http.Client,
 			accessToken: accessToken,
 		},
 		query:     query,
+		branchMap: map[string]string{},
 	}
 }
 
+func (gc githubCrawler) SetDefaultBranch(repo, branch string) {
+	gc.branchMap[repo] = branch
+}
+
+func (gc githubCrawler) DefaultBranch(repo string) string {
+	return gc.branchMap[repo]
+}
+
 // Implements crawler.Crawler.
-func (gc githubCrawler) Crawl(
-	ctx context.Context, output chan<- crawler.CrawledDocument) error {
+func (gc githubCrawler) Crawl(ctx context.Context,
+	output chan<- crawler.CrawledDocument, seen map[string]struct{}) error {
 
 	noETagClient := GhClient{
 		RequestConfig: gc.client.RequestConfig,
@@ -79,17 +90,26 @@ func (gc githubCrawler) Crawl(
 
 	// Query each range for files.
 	errs := make(multiError, 0)
+	queryResult := RangeQueryResult{}
 	for _, query := range ranges {
-		err := processQuery(ctx, gc.client, query, output)
+		result, err := processQuery(ctx, gc.client, query, output, seen, gc.branchMap)
 		if err != nil {
 			errs = append(errs, err)
 		}
+		queryResult.totalDocCnt += result.totalDocCnt
+		queryResult.seenDocCnt += result.seenDocCnt
+		queryResult.newDocCnt += result.newDocCnt
+		queryResult.errorCnt += result.errorCnt
 	}
 
 	if len(errs) > 0 {
 		return errs
 	}
-
+	logger.Printf("Summary of Crawl: got %d files from Github. "+
+		"%d have been seen before. %d are new and sent to the output channel." +
+		"%d have kustomizationResultAdapter errors.",
+		queryResult.totalDocCnt, queryResult.seenDocCnt,
+		queryResult.newDocCnt, queryResult.errorCnt)
 	return nil
 }
 
@@ -100,7 +120,7 @@ func (gc githubCrawler) FetchDocument(_ context.Context, d *doc.Document) error
 	// set the default branch if it is empty
 	if d.DefaultBranch == "" {
 		url := gc.client.ReposRequest(d.RepositoryFullName())
-		defaultBranch, err := gc.client.GetDefaultBranch(url)
+		defaultBranch, err := gc.client.GetDefaultBranch(url, d.RepositoryURL, gc.branchMap)
 		if err != nil {
 			logger.Printf(
 				"(error: %v) setting default_branch to master\n", err)
@@ -108,6 +128,8 @@ func (gc githubCrawler) FetchDocument(_ context.Context, d *doc.Document) error
 		}
 		d.DefaultBranch = defaultBranch
 	}
+	gc.SetDefaultBranch(d.RepositoryURL, d.DefaultBranch)
+
 	repoURL := d.RepositoryURL + "/" + d.FilePath + "?ref=" + d.DefaultBranch
 	repoSpec, err := git.NewRepoSpecFromUrl(repoURL)
 	if err != nil {
@@ -176,10 +198,18 @@ func (gc githubCrawler) Match(d *doc.Document) bool {
 	return strings.Contains(repoSpec.Host, "github.com")
 }
 
+type RangeQueryResult struct {
+	totalDocCnt uint64
+	seenDocCnt   uint64
+	newDocCnt uint64
+	errorCnt  uint64
+}
+
 // processQuery follows all of the pages in a query, and updates/adds the
 // documents from the crawl to the datastore/index.
 func processQuery(ctx context.Context, gcl GhClient, query string,
-	output chan<- crawler.CrawledDocument) error {
+	output chan<- crawler.CrawledDocument, seen map[string]struct{},
+	branchMap map[string]string) (RangeQueryResult, error) {
 
 	queryPages := make(chan GhResponseInfo)
 
@@ -196,50 +226,75 @@ func processQuery(ctx context.Context, gcl GhClient, query string,
 	}()
 
 	errs := make(multiError, 0)
-	errorCnt := 0
-	totalCnt := 0
+	result := RangeQueryResult{}
+	pageID := 1
 	for page := range queryPages {
 		if page.Error != nil {
 			errs = append(errs, page.Error)
 			continue
 		}
-
+		var errorCnt, seenDocCnt, newDocCnt, totalDocCnt uint64
 		for _, file := range page.Parsed.Items {
-			k, err := kustomizationResultAdapter(gcl, file)
+			k, err := kustomizationResultAdapter(gcl, file, seen, branchMap)
 			if err != nil {
 				logger.Printf("kustomizationResultAdapter failed: %v", err)
 				errs = append(errs, err)
 				errorCnt++
 			}
 			if k != nil {
+				newDocCnt++
 				output <- k
+			} else {
+				seenDocCnt++
 			}
-			totalCnt++
+			totalDocCnt++
 		}
 
-		logger.Printf("got %d files out of %d from API. %d of %d had errors\n",
-			totalCnt, page.Parsed.TotalCount, errorCnt, totalCnt)
+		logger.Printf("processQuery [page %d]: got %d files out of %d from API. "+
+			"%d have been seen before. %d are new and sent to the output channel." +
+			"%d have kustomizationResultAdapter errors.",
+			pageID, totalDocCnt, page.Parsed.TotalCount, seenDocCnt, newDocCnt, errorCnt)
+		result.totalDocCnt += totalDocCnt
+		result.seenDocCnt += seenDocCnt
+		result.newDocCnt += newDocCnt
+		result.errorCnt += errorCnt
+
+		pageID++
 	}
 
-	return errs
+	logger.Printf("Summary of processQuery: got %d files from API. "+
+		"%d have been seen before. %d are new and sent to the output channel." +
+		" %d have kustomizationResultAdapter errors.",
+		result.totalDocCnt, result.seenDocCnt, result.newDocCnt, result.errorCnt)
+
+	return result, errs
 }
 
-func kustomizationResultAdapter(gcl GhClient, k GhFileSpec) (
-	crawler.CrawledDocument, error) {
-
-	data, err := gcl.GetFileData(k)
-	if err != nil {
-		return nil, err
-	}
-
+func kustomizationResultAdapter(gcl GhClient, k GhFileSpec, seen map[string]struct{},
+	branchMap map[string]string) (crawler.CrawledDocument, error) {
 	url := gcl.ReposRequest(k.Repository.FullName)
-	defaultBranch, err := gcl.GetDefaultBranch(url)
+	defaultBranch, err := gcl.GetDefaultBranch(url, k.Repository.URL, branchMap)
 	if err != nil {
 		logger.Printf(
 			"(error: %v) setting default_branch to master\n", err)
 		defaultBranch = "master"
 	}
 
+	document := doc.Document{
+		FilePath:      k.Path,
+		DefaultBranch: defaultBranch,
+		RepositoryURL: k.Repository.URL,
+	}
+
+	if _, ok := seen[document.ID()]; ok {
+		return nil, nil
+	}
+
+	data, err := gcl.GetFileData(k)
+	if err != nil {
+		return nil, err
+	}
+
 	d := doc.KustomizationDocument{
 		Document: doc.Document{
 			DocumentData:  string(data),
@@ -344,7 +399,15 @@ func CloseResponseBody(resp *http.Response) {
 	}
 }
 
-func (gcl GhClient) GetDefaultBranch(url string) (string, error) {
+// GetDefaultBranch gets the default branch of a github repository.
+// m is a map which maps a github repository to its default branch.
+// If repo is already in m, the default branch for url will be obtained from m;
+// otherwise, a query will be made to github to obtain the default branch.
+func (gcl GhClient) GetDefaultBranch(url, repo string, m map[string]string) (string, error) {
+	if v, ok := m[repo]; ok {
+		return v, nil
+	}
+
 	resp, err := gcl.GetReposData(url)
 	if err != nil {
 		return "", fmt.Errorf(