Merge pull request #56 from priyawadhwa/mtime

Add --snapshot-mode flag to allow only considering mtime when snapshotting

executor/cmd/root.go

@@ -17,6 +17,7 @@ limitations under the License.
 package cmd
 
 import (
+	"fmt"
 	"github.com/GoogleCloudPlatform/k8s-container-builder/pkg/commands"
 	"github.com/GoogleCloudPlatform/k8s-container-builder/pkg/constants"
 	"github.com/GoogleCloudPlatform/k8s-container-builder/pkg/dockerfile"
@@ -37,6 +38,7 @@ var (
 	dockerfilePath string
 	destination    string
 	srcContext     string
+	snapshotMode   string
 	bucket         string
 	logLevel       string
 )
@@ -46,6 +48,7 @@ func init() {
 	RootCmd.PersistentFlags().StringVarP(&srcContext, "context", "c", "", "Path to the dockerfile build context.")
 	RootCmd.PersistentFlags().StringVarP(&bucket, "bucket", "b", "", "Name of the GCS bucket from which to access build context as tarball.")
 	RootCmd.PersistentFlags().StringVarP(&destination, "destination", "d", "", "Registry the final image should be pushed to (ex: gcr.io/test/example:latest)")
+	RootCmd.PersistentFlags().StringVarP(&snapshotMode, "snapshotMode", "", "full", "Set this flag to change the file attributes inspected during snapshotting")
 	RootCmd.PersistentFlags().StringVarP(&logLevel, "verbosity", "v", constants.DefaultLogLevel, "Log level (debug, info, warn, error, fatal, panic")
 }
 
@@ -121,7 +124,11 @@ func execute() error {
 		return err
 	}
 
-	l := snapshot.NewLayeredMap(util.Hasher())
+	hasher, err := getHasher()
+	if err != nil {
+		return err
+	}
+	l := snapshot.NewLayeredMap(hasher)
 	snapshotter := snapshot.NewSnapshotter(l, constants.RootDir)
 
 	// Take initial snapshot
@@ -179,6 +186,17 @@ func execute() error {
 	return image.PushImage(sourceImage, destination)
 }
 
+func getHasher() (func(string) (string, error), error) {
+	if snapshotMode == constants.SnapshotModeTime {
+		logrus.Info("Only file modification time will be considered when snapshotting")
+		return util.MtimeHasher(), nil
+	}
+	if snapshotMode == constants.SnapshotModeFull {
+		return util.Hasher(), nil
+	}
+	return nil, fmt.Errorf("%s is not a valid snapshot mode", snapshotMode)
+}
+
 func resolveOnBuild(stage *instructions.Stage, config *manifest.Schema2Config) error {
 	if config.OnBuild == nil {
 		return nil

integration_tests/integration_test_yaml.go

@@ -45,6 +45,7 @@ var fileTests = []struct {
 	kanikoContext       string
 	kanikoContextBucket bool
 	repo                string
+	snapshotMode        string
 }{
 	{
 		description:    "test extract filesystem",
@@ -53,6 +54,7 @@ var fileTests = []struct {
 		dockerContext:  dockerfilesPath,
 		kanikoContext:  dockerfilesPath,
 		repo:           "extract-filesystem",
+		snapshotMode:   "time",
 	},
 	{
 		description:    "test run",
@@ -69,6 +71,7 @@ var fileTests = []struct {
 		dockerContext:  dockerfilesPath,
 		kanikoContext:  dockerfilesPath,
 		repo:           "test-run-2",
+		snapshotMode:   "time",
 	},
 	{
 		description:    "test copy",
@@ -77,6 +80,7 @@ var fileTests = []struct {
 		dockerContext:  buildcontextPath,
 		kanikoContext:  buildcontextPath,
 		repo:           "test-copy",
+		snapshotMode:   "time",
 	},
 	{
 		description:         "test bucket build context",
@@ -231,13 +235,17 @@ func main() {
 
 		// Then, buld the image with kaniko
 		kanikoImage := testRepo + kanikoPrefix + test.repo
+		snapshotMode := ""
+		if test.snapshotMode != "" {
+			snapshotMode = "--snapshotMode=" + test.snapshotMode
+		}
 		contextFlag := "--context"
 		if test.kanikoContextBucket {
 			contextFlag = "--bucket"
 		}
 		kaniko := step{
 			Name: executorImage,
-			Args: []string{"--destination", kanikoImage, "--dockerfile", test.dockerfilePath, contextFlag, test.kanikoContext},
+			Args: []string{"--destination", kanikoImage, "--dockerfile", test.dockerfilePath, contextFlag, test.kanikoContext, snapshotMode},
 		}
 
 		// Pull the kaniko image

pkg/constants/constants.go

@@ -39,4 +39,8 @@ const (
 	// BuildContextDir is the directory a build context will be unpacked into,
 	// for example, a tarball from a GCS bucket will be unpacked here
 	BuildContextDir = "/kaniko/buildcontext/"
+
+	// Various snapshot modes:
+	SnapshotModeTime = "time"
+	SnapshotModeFull = "full"
 )

pkg/util/util.go

@@ -61,3 +61,17 @@ func Hasher() func(string) (string, error) {
 	}
 	return hasher
 }
+
+// Hasher returns a hash function, which only looks at mtime to determine if a file has changed
+func MtimeHasher() func(string) (string, error) {
+	hasher := func(p string) (string, error) {
+		h := md5.New()
+		fi, err := os.Lstat(p)
+		if err != nil {
+			return "", err
+		}
+		h.Write([]byte(fi.ModTime().String()))
+		return hex.EncodeToString(h.Sum(nil)), nil
+	}
+	return hasher
+}