pkg/payload/image: avoid rendering manifests

The `image` command currently loads the image-references file and then
renders all manifests. Clearly the manifest rendering can be avoided
when we just want to look up an image reference.

This command is currently run 17 times by bootkube, and my quick test
shows this refactor halving the roughly 10 seconds this takes.

The main refactoring here is to split the loadUpdatePayloadMetadata()
function into getPayloadTasks() and loadImageReferences() so that the
latter can be used standalone in this particular case.

Author: markmc

pkg/payload/image.go

@@ -2,19 +2,26 @@ package payload
 
 import (
 	"fmt"
+	"path/filepath"
 
 	"github.com/pkg/errors"
 )
 
 // ImageForShortName returns the image using the updatepayload embedded in
 // the Operator.
 func ImageForShortName(name string) (string, error) {
-	up, err := LoadUpdate(DefaultPayloadDir, "")
+	if err := ValidateDirectory(DefaultPayloadDir); err != nil {
+		return "", err
+	}
+
+	releaseDir := filepath.Join(DefaultPayloadDir, ReleaseManifestDir)
+
+	imageRef, err := loadImageReferences(releaseDir)
 	if err != nil {
-		return "", errors.Wrapf(err, "error loading release manifests from %q", DefaultPayloadDir)
+		return "", errors.Wrapf(err, "error loading image references from %q", releaseDir)
 	}
 
-	for _, tag := range up.ImageRef.Spec.Tags {
+	for _, tag := range imageRef.Spec.Tags {
 		if tag.Name == name {
 			// we found the short name in ImageStream
 			if tag.From != nil && tag.From.Kind == "DockerImage" {

pkg/payload/payload.go

@@ -216,22 +216,23 @@ func loadUpdatePayloadMetadata(dir, releaseImage string) (*Update, []payloadTask
 		releaseDir = filepath.Join(dir, ReleaseManifestDir)
 	)
 
-	// XXX: load cincinnatiJSONFile
-	cjf := filepath.Join(releaseDir, cincinnatiJSONFile)
-	// XXX: load imageReferencesFile
-	irf := filepath.Join(releaseDir, imageReferencesFile)
-	imageRefData, err := ioutil.ReadFile(irf)
+	imageRef, err := loadImageReferences(releaseDir)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	imageRef, err := resourceread.ReadImageStreamV1(imageRefData)
-	if err != nil {
-		return nil, nil, errors.Wrapf(err, "invalid image-references data %s", irf)
-	}
+	tasks := getPayloadTasks(releaseDir, cvoDir, releaseImage)
+
+	return &Update{ImageRef: imageRef, ReleaseImage: releaseImage, ReleaseVersion: imageRef.Name}, tasks, nil
+}
+
+func getPayloadTasks(releaseDir, cvoDir, releaseImage string) []payloadTasks {
+	cjf := filepath.Join(releaseDir, cincinnatiJSONFile)
+	irf := filepath.Join(releaseDir, imageReferencesFile)
 
 	mrc := manifestRenderConfig{ReleaseImage: releaseImage}
-	tasks := []payloadTasks{{
+
+	return []payloadTasks{{
 		idir:       cvoDir,
 		preprocess: func(ib []byte) ([]byte, error) { return renderManifest(mrc, ib) },
 		skipFiles:  sets.NewString(),
@@ -240,5 +241,19 @@ func loadUpdatePayloadMetadata(dir, releaseImage string) (*Update, []payloadTask
 		preprocess: nil,
 		skipFiles:  sets.NewString(cjf, irf),
 	}}
-	return &Update{ImageRef: imageRef, ReleaseImage: releaseImage, ReleaseVersion: imageRef.Name}, tasks, nil
+}
+
+func loadImageReferences(releaseDir string) (*imagev1.ImageStream, error) {
+	irf := filepath.Join(releaseDir, imageReferencesFile)
+	imageRefData, err := ioutil.ReadFile(irf)
+	if err != nil {
+		return nil, err
+	}
+
+	imageRef, err := resourceread.ReadImageStreamV1(imageRefData)
+	if err != nil {
+		return nil, errors.Wrapf(err, "invalid image-references data %s", irf)
+	}
+
+	return imageRef, nil
 }