Crawler performance improvements, better structure

Refactored the crawler implementation to make the whole thing more
testable. Added a document interface to make the crawler generic.
This will be useful for collecting plugins, and other documents.

internal/tools/crawler/crawler.go

@@ -6,11 +6,19 @@ package crawler
 import (
 	"context"
 	"fmt"
+	"log"
+	"os"
 	"sync"
 
+	_ "github.com/gomodule/redigo/redis"
+
 	"sigs.k8s.io/kustomize/internal/tools/doc"
 )
 
+var (
+	logger = log.New(os.Stdout, "Crawler: ", log.LstdFlags|log.LUTC|log.Llongfile)
+)
+
 // Crawler forwards documents from source repositories to index and store them
 // for searching. Each crawler is responsible for querying it's source of
 // information, and forwarding files that have not been seen before or that need
@@ -19,7 +27,152 @@ 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<- *doc.KustomizationDocument) error
+	Crawl(ctx context.Context, output chan<- CrawlerDocument) error
+
+	// Get the document data given the FilePath, Repo, and Ref/Tag/Branch.
+	FetchDocument(context.Context, *doc.Document) error
+	// Write to the document what the created time is.
+	SetCreated(context.Context, *doc.Document) error
+
+	Match(*doc.Document) bool
+}
+
+type CrawlerDocument interface {
+	ID() string
+	GetDocument() *doc.Document
+	GetResources() ([]*doc.Document, error)
+	WasCached() bool
+}
+
+type CrawlerSeed []*doc.Document
+
+type IndexFunc func(CrawlerDocument, Crawler) error
+type Converter func(*doc.Document) (CrawlerDocument, error)
+
+// Cleaner, more efficient, and more extensible crawler implementation.
+// The seed must include the ids of each document in the index.
+func CrawlFromSeed(ctx context.Context, seed CrawlerSeed,
+	crawlers []Crawler, conv Converter, indx IndexFunc) {
+
+	seen := make(map[string]struct{})
+
+	logIfErr := func(err error) {
+		if err == nil {
+			return
+		}
+		logger.Println("error: ", err)
+	}
+
+	stack := make(CrawlerSeed, 0)
+
+	findMatch := func(d *doc.Document) Crawler {
+		for _, crawl := range crawlers {
+			if crawl.Match(d) {
+				return crawl
+			}
+		}
+
+		return nil
+	}
+
+	addBranches := func(cdoc CrawlerDocument, match Crawler) {
+		if _, ok := seen[cdoc.ID()]; ok {
+			return
+		}
+
+		seen[cdoc.ID()] = struct{}{}
+		// Insert into index
+		err := indx(cdoc, match)
+		logIfErr(err)
+		if err != nil {
+			return
+		}
+
+		deps, err := cdoc.GetResources()
+		logIfErr(err)
+		if err != nil {
+			return
+		}
+		for _, dep := range deps {
+			if _, ok := seen[dep.ID()]; ok {
+				continue
+			}
+			stack = append(stack, dep)
+		}
+	}
+
+	doCrawl := func(docsPtr *CrawlerSeed) {
+		for len(*docsPtr) > 0 {
+			back := len(*docsPtr) - 1
+			next := (*docsPtr)[back]
+			*docsPtr = (*docsPtr)[:back]
+
+			match := findMatch(next)
+			if match == nil {
+				logIfErr(fmt.Errorf(
+					"%v could not match any crawler", next))
+				continue
+			}
+
+			err := match.FetchDocument(ctx, next)
+			logIfErr(err)
+			// If there was no change or there is an error, we don't have
+			// to branch out, since the dependencies are already in the
+			// index, or we cannot find the document.
+			if err != nil || next.WasCached() {
+				continue
+			}
+
+			cdoc, err := conv(next)
+			logIfErr(err)
+			if err != nil {
+				continue
+			}
+
+			addBranches(cdoc, match)
+		}
+	}
+	// Exploit seed to update bulk of corpus.
+	logger.Printf("updating %d documents from seed\n", len(seed))
+	doCrawl(&seed)
+	// Traverse any new links added while updating corpus.
+	logger.Printf("crawling %d new documents found in the seed\n", len(stack))
+	doCrawl(&stack)
+
+	ch := make(chan CrawlerDocument, 1<<10)
+	wg := sync.WaitGroup{}
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for cdoc := range ch {
+			if _, ok := seen[cdoc.ID()]; ok {
+				continue
+			}
+			match := findMatch(cdoc.GetDocument())
+			if match == nil {
+				logIfErr(fmt.Errorf(
+					"%v could not match any crawler", cdoc))
+				continue
+			}
+			addBranches(cdoc, match)
+		}
+	}()
+
+	// Exploration through APIs.
+	errs := CrawlerRunner(ctx, ch, crawlers)
+	if errs != nil {
+		for _, err := range errs {
+			logIfErr(err)
+		}
+	}
+	close(ch)
+	logger.Println("Processing the new documents from the crawlers' exploration.")
+	wg.Wait()
+	// Handle deps of newly discovered documents.
+	logger.Printf("crawling the %d new documents from the crawlers' exploration.",
+		len(stack))
+	doCrawl(&stack)
 }
 
 // CrawlerRunner is a blocking function and only returns once all of the
@@ -32,21 +185,28 @@ type Crawler interface {
 // The return value is an array of errors in which each index represents the
 // index of the crawler that emitted the error. Although the errors themselves
 // can be nil, the array will always be exactly the size of the crawlers array.
+//
+// Crawler Runner takes in a seed, which represents the documents stored in an
+// index somewhere. The document data is not required to be populated. If there
+// are many documents, this is preferable. The order of iteration over the seed
+// is not garanteed, but the CrawlerRunner does guarantee that every element
+// from the seed will be processed before any other documents from the
+// crawlers.
 func CrawlerRunner(ctx context.Context,
-	output chan<- *doc.KustomizationDocument, crawlers []Crawler) []error {
+	output chan<- CrawlerDocument, crawlers []Crawler) []error {
 
 	errs := make([]error, len(crawlers))
 	wg := sync.WaitGroup{}
 
 	for i, crawler := range crawlers {
 		// Crawler implementations get their own channels to prevent a
 		// crawler from closing the main output channel.
-		docs := make(chan *doc.KustomizationDocument)
+		docs := make(chan CrawlerDocument)
 		wg.Add(2)
 
 		// Forward all of the documents from this crawler's channel to
 		// the main output channel.
-		go func(docs <-chan *doc.KustomizationDocument) {
+		go func(docs <-chan CrawlerDocument) {
 			defer wg.Done()
 			for doc := range docs {
 				output <- doc
@@ -55,7 +215,7 @@ func CrawlerRunner(ctx context.Context,
 
 		// Run this crawler and capture its returned error.
 		go func(idx int, crawler Crawler,
-			docs chan<- *doc.KustomizationDocument) {
+			docs chan<- CrawlerDocument) {
 
 			defer func() {
 				wg.Done()