apply relocation map at runtime

Bundle definition -with service image definitions- is mounted under
`/cnab/bundle.json` in the invocation image.
If a `/cnab/app/relocation-mapping.json` exists read it and apply it
on top of image definitions.

See https://github.com/cnabio/cnab-spec/blob/master/103-bundle-runtime.md#image-relocation

Signed-off-by: Yves Brissaud <yves.brissaud@docker.com>

Author: eunomie

cmd/cnab-run/bundle.go

@@ -3,13 +3,38 @@ package main
 import (
 	"github.com/deislabs/cnab-go/bundle"
 	"github.com/docker/app/internal/relocated"
+	"github.com/docker/cnab-to-oci/relocation"
 )
 
 const (
 	// bundlePath is where the CNAB runtime will put the actual Bundle definition
 	bundlePath = "/cnab/bundle.json"
+	// relocationMapPath is where the CNAB runtime will put the relocation map
+	// See https://github.com/cnabio/cnab-spec/blob/master/103-bundle-runtime.md#image-relocation
+	relocationMapPath = "/cnab/app/relocation-mapping.json"
 )
 
 func getBundle() (*bundle.Bundle, error) {
 	return relocated.BundleJSON(bundlePath)
 }
+
+func getRelocationMap() (relocation.ImageRelocationMap, error) {
+	return relocated.RelocationMapJSON(relocationMapPath)
+}
+
+func getRelocatedBundle() (*relocated.Bundle, error) {
+	bndl, err := getBundle()
+	if err != nil {
+		return nil, err
+	}
+
+	relocationMap, err := getRelocationMap()
+	if err != nil {
+		return nil, err
+	}
+
+	return &relocated.Bundle{
+		Bundle:        bndl,
+		RelocationMap: relocationMap,
+	}, nil
+}

cmd/cnab-run/inspect.go

@@ -15,11 +15,11 @@ func inspectAction(instanceName string) error {
 	}
 	defer app.Cleanup()
 
-	bndl, err := getBundle()
+	bndl, err := getRelocatedBundle()
 	if err != nil {
 		return err
 	}
 
 	parameters := packager.ExtractCNABParametersValues(packager.ExtractCNABParameterMapping(app.Parameters()), os.Environ())
-	return appinspect.ImageInspect(os.Stdout, app, parameters, bndl.Images)
+	return appinspect.ImageInspect(os.Stdout, app, parameters, bndl.RelocatedImages())
 }

cmd/cnab-run/install.go

@@ -35,12 +35,12 @@ func installAction(instanceName string) error {
 	if err != nil {
 		return err
 	}
-	bndl, err := getBundle()
+	bndl, err := getRelocatedBundle()
 	if err != nil {
 		return err
 	}
 	parameters := packager.ExtractCNABParametersValues(packager.ExtractCNABParameterMapping(app.Parameters()), os.Environ())
-	rendered, err := render.Render(app, parameters, bndl.Images)
+	rendered, err := render.Render(app, parameters, bndl.RelocatedImages())
 	if err != nil {
 		return err
 	}

cmd/cnab-run/render.go

@@ -19,7 +19,7 @@ func renderAction(instanceName string) error {
 	}
 	defer app.Cleanup()
 
-	bndl, err := getBundle()
+	bndl, err := getRelocatedBundle()
 	if err != nil {
 		return err
 	}
@@ -31,7 +31,7 @@ func renderAction(instanceName string) error {
 
 	parameters := packager.ExtractCNABParametersValues(packager.ExtractCNABParameterMapping(app.Parameters()), os.Environ())
 
-	rendered, err := render.Render(app, parameters, bndl.Images)
+	rendered, err := render.Render(app, parameters, bndl.RelocatedImages())
 	if err != nil {
 		return err
 	}

internal/relocated/bundle.go

@@ -38,7 +38,7 @@ func BundleFromFile(filename string) (*Bundle, error) {
 	}
 
 	relocationMapFileName := filepath.Join(filepath.Dir(filename), RelocationMapFilename)
-	relocationMap, err := relocationMapJSON(relocationMapFileName)
+	relocationMap, err := RelocationMapJSON(relocationMapFileName)
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to read relocation map")
 	}
@@ -87,10 +87,11 @@ func BundleJSON(bundlePath string) (*bundle.Bundle, error) {
 	return bndl, nil
 }
 
-func relocationMapJSON(relocationMapPath string) (relocation.ImageRelocationMap, error) {
+func RelocationMapJSON(relocationMapPath string) (relocation.ImageRelocationMap, error) {
 	relocationMap := relocation.ImageRelocationMap{}
 	_, err := os.Stat(relocationMapPath)
 	if os.IsNotExist(err) {
+		// it's ok to not have a relocation map, just act as if the file were empty
 		return relocationMap, nil
 	}
 	data, err := ioutil.ReadFile(relocationMapPath)
@@ -102,3 +103,15 @@ func relocationMapJSON(relocationMapPath string) (relocation.ImageRelocationMap,
 	}
 	return relocationMap, nil
 }
+
+func (b *Bundle) RelocatedImages() map[string]bundle.Image {
+	images := b.Images
+	for name, def := range images {
+		if img, ok := b.RelocationMap[def.Image]; ok {
+			def.Image = img
+			images[name] = def
+		}
+	}
+
+	return images
+}