Improve cache layer uploads. (#443)

This change only uploads layers that were created from cache misses on RUN commands.
It also improves the cache-checking logic to handle this case.
Finally, it makes cache layer uploads happen in parallel with the rest of the build, logging
a warning if any fail.

pkg/commands/base_command.go

@@ -43,3 +43,7 @@ func (b *BaseCommand) MetadataOnly() bool {
 func (b *BaseCommand) RequiresUnpackedFS() bool {
 	return false
 }
+
+func (b *BaseCommand) ShouldCacheOutput() bool {
+	return false
+}

pkg/commands/commands.go

@@ -36,6 +36,7 @@ type DockerCommand interface {
 	String() string
 	// A list of files to snapshot, empty for metadata commands or nil if we don't know
 	FilesToSnapshot() []string
+
 	// Return a cache-aware implementation of this command, if it exists.
 	CacheCommand(v1.Image) DockerCommand
 
@@ -45,6 +46,8 @@ type DockerCommand interface {
 	MetadataOnly() bool
 
 	RequiresUnpackedFS() bool
+
+	ShouldCacheOutput() bool
 }
 
 func GetCommand(cmd instructions.Command, buildcontext string) (DockerCommand, error) {

pkg/commands/run.go

@@ -169,6 +169,10 @@ func (r *RunCommand) RequiresUnpackedFS() bool {
 	return true
 }
 
+func (r *RunCommand) ShouldCacheOutput() bool {
+	return true
+}
+
 type CachingRunCommand struct {
 	BaseCommand
 	img            v1.Image

pkg/executor/build.go

@@ -23,6 +23,8 @@ import (
 	"strconv"
 	"time"
 
+	"golang.org/x/sync/errgroup"
+
 	"github.com/google/go-containerregistry/pkg/name"
 	"github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/mutate"
@@ -119,15 +121,17 @@ func (s *stageBuilder) optimize(compositeKey CompositeCache, cfg v1.Config, cmds
 		if err != nil {
 			return err
 		}
-		img, err := layerCache.RetrieveLayer(ck)
-		if err != nil {
-			logrus.Infof("No cached layer found for cmd %s", command.String())
-			break
-		}
+		if command.ShouldCacheOutput() {
+			img, err := layerCache.RetrieveLayer(ck)
+			if err != nil {
+				logrus.Infof("No cached layer found for cmd %s", command.String())
+				break
+			}
 
-		if cacheCmd := command.CacheCommand(img); cacheCmd != nil {
-			logrus.Infof("Using caching version of cmd: %s", command.String())
-			cmds[i] = cacheCmd
+			if cacheCmd := command.CacheCommand(img); cacheCmd != nil {
+				logrus.Infof("Using caching version of cmd: %s", command.String())
+				cmds[i] = cacheCmd
+			}
 		}
 
 		// Mutate the config for any commands that require it.
@@ -184,6 +188,7 @@ func (s *stageBuilder) build() error {
 		return err
 	}
 
+	cacheGroup := errgroup.Group{}
 	for index, command := range cmds {
 		if command == nil {
 			continue
@@ -222,10 +227,19 @@ func (s *stageBuilder) build() error {
 		if err != nil {
 			return err
 		}
-		if err := s.saveSnapshotToImage(command.String(), ck, tarPath); err != nil {
+		// Push layer to cache (in parallel) now along with new config file
+		if s.opts.Cache && command.ShouldCacheOutput() {
+			cacheGroup.Go(func() error {
+				return pushLayerToCache(s.opts, ck, tarPath, command.String())
+			})
+		}
+		if err := s.saveSnapshotToImage(command.String(), tarPath); err != nil {
 			return err
 		}
 	}
+	if err := cacheGroup.Wait(); err != nil {
+		logrus.Warnf("error uploading layer to cache: %s", err)
+	}
 	return nil
 }
 
@@ -266,7 +280,7 @@ func (s *stageBuilder) shouldTakeSnapshot(index int, files []string) bool {
 	return true
 }
 
-func (s *stageBuilder) saveSnapshotToImage(createdBy string, ck string, tarPath string) error {
+func (s *stageBuilder) saveSnapshotToImage(createdBy string, tarPath string) error {
 	if tarPath == "" {
 		return nil
 	}
@@ -283,12 +297,6 @@ func (s *stageBuilder) saveSnapshotToImage(createdBy string, ck string, tarPath
 	if err != nil {
 		return err
 	}
-	// Push layer to cache now along with new config file
-	if s.opts.Cache {
-		if err := pushLayerToCache(s.opts, ck, layer, createdBy); err != nil {
-			return err
-		}
-	}
 	s.image, err = mutate.Append(s.image,
 		mutate.Addendum{
 			Layer: layer,

pkg/executor/push.go

@@ -107,7 +107,11 @@ func DoPush(image v1.Image, opts *config.KanikoOptions) error {
 
 // pushLayerToCache pushes layer (tagged with cacheKey) to opts.Cache
 // if opts.Cache doesn't exist, infer the cache from the given destination
-func pushLayerToCache(opts *config.KanikoOptions, cacheKey string, layer v1.Layer, createdBy string) error {
+func pushLayerToCache(opts *config.KanikoOptions, cacheKey string, tarPath string, createdBy string) error {
+	layer, err := tarball.LayerFromFile(tarPath)
+	if err != nil {
+		return err
+	}
 	cache, err := cache.Destination(opts, cacheKey)
 	if err != nil {
 		return errors.Wrap(err, "getting cache destination")