Allow store to docker multiarch builds

We do not allow to load into docker images that are targets another
platform differ from current arch. Assume this is because of no support
of manifest. But we can keep all images in place by adding arch suffix
and using tag without arch suffix to point onto current system arch. It
will help to use images from docker for another arch.

Signed-off-by: Petr Fedchenkov <giggsoff@gmail.com>

src/cmd/linuxkit/pkglib/build.go

@@ -191,20 +191,6 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 		return errors.New("must provide linuxkit build cache directory")
 	}
 
-	// if targeting docker, be sure local arch is a build target
-	if bo.targetDocker {
-		var found bool
-		for _, platform := range bo.platforms {
-			if platform.Architecture == arch {
-				found = true
-				break
-			}
-		}
-		if !found {
-			return fmt.Errorf("must build for local platform 'linux/%s' when targeting docker", arch)
-		}
-	}
-
 	if p.git != nil && bo.push && bo.release == "" {
 		r, err := p.git.commitTag("HEAD")
 		if err != nil {
@@ -243,6 +229,24 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 		} else {
 			fmt.Fprintf(writer, "%s not found\n", ref)
 		}
+		if bo.targetDocker {
+			notFound := false
+			for _, platform := range bo.platforms {
+				archRef, err := reference.Parse(fmt.Sprintf("%s-%s", p.FullTag(), platform.Architecture))
+				if err != nil {
+					return err
+				}
+				fmt.Fprintf(writer, "checking for %s in local cache, fallback to remote registry...\n", archRef)
+				if _, err := c.ImagePull(&archRef, "", platform.Architecture, false); err == nil {
+					fmt.Fprintf(writer, "%s found or pulled\n", archRef)
+					skipBuild = true
+				} else {
+					fmt.Fprintf(writer, "%s not found\n", archRef)
+					notFound = true
+				}
+			}
+			skipBuild = skipBuild && !notFound
+		}
 	}
 
 	if !skipBuild {
@@ -327,14 +331,28 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 	}
 
 	// if requested docker, load the image up
+	// we will store images with arch suffix, i.e. -amd64
+	// if one of the arch equals with system, we will add tag without suffix
 	if bo.targetDocker {
-		cacheSource := c.NewSource(&ref, arch, desc)
+		for _, platform := range bo.platforms {
-		reader, err := cacheSource.V1TarReader()
+			archRef, err := reference.Parse(fmt.Sprintf("%s-%s", p.FullTag(), platform.Architecture))
-		if err != nil {
+			if err != nil {
-			return fmt.Errorf("unable to get reader from cache: %v", err)
+				return err
-		}
+			}
-		if err := d.load(reader); err != nil {
+			cacheSource := c.NewSource(&archRef, platform.Architecture, desc)
-			return err
+			reader, err := cacheSource.V1TarReader()
+			if err != nil {
+				return fmt.Errorf("unable to get reader from cache: %v", err)
+			}
+			if err := d.load(reader); err != nil {
+				return err
+			}
+			if platform.Architecture == arch {
+				err = d.tag(fmt.Sprintf("%s-%s", p.FullTag(), platform.Architecture), p.FullTag())
+				if err != nil {
+					return err
+				}
+			}
 		}
 	}
 
@@ -375,9 +393,18 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 	}
 
 	// tag in docker, if requested
+	// will tag all images with arch suffix
+	// if one of the arch equals with system will add tag without suffix
 	if bo.targetDocker {
-		if err := d.tag(p.FullTag(), fullRelTag); err != nil {
+		for _, platform := range bo.platforms {
-			return err
+			if err := d.tag(fmt.Sprintf("%s-%s", p.FullTag(), platform.Architecture), fmt.Sprintf("%s-%s", fullRelTag, platform.Architecture)); err != nil {
+				return err
+			}
+			if platform.Architecture == arch {
+				if err := d.tag(fmt.Sprintf("%s-%s", p.FullTag(), platform.Architecture), fullRelTag); err != nil {
+					return err
+				}
+			}
 		}
 	}
 

src/cmd/linuxkit/pkglib/build_test.go

@@ -9,7 +9,6 @@ import (
 	"io"
 	"io/ioutil"
 	"math/rand"
-	"runtime"
 	"strings"
 	"testing"
 
@@ -116,7 +115,7 @@ func (c *cacheMocker) ImageLoad(ref *reference.Spec, architecture string, r io.R
 }
 
 func (c *cacheMocker) imageWriteStream(ref *reference.Spec, architecture string, r io.Reader) (lktspec.ImageSource, error) {
-	image := ref.String()
+	image := fmt.Sprintf("%s-%s", ref.String(), architecture)
 
 	// make some random data for a layer
 	b, err := ioutil.ReadAll(r)
@@ -154,10 +153,14 @@ func (c *cacheMocker) imageWriteStream(ref *reference.Spec, architecture string,
 		Annotations: map[string]string{
 			imagespec.AnnotationRefName: image,
 		},
+		Platform: &registry.Platform{
+			OS:           "linux",
+			Architecture: architecture,
+		},
 	}
 	c.appendImage(image, desc)
 
-	return c.NewSource(ref, "", &desc), nil
+	return c.NewSource(ref, architecture, &desc), nil
 }
 
 func (c *cacheMocker) IndexWrite(ref *reference.Spec, descriptors ...registry.Descriptor) (lktspec.ImageSource, error) {
@@ -273,7 +276,13 @@ func (c cacheMockerSource) TarReader() (io.ReadCloser, error) {
 	return nil, errors.New("unsupported")
 }
 func (c cacheMockerSource) V1TarReader() (io.ReadCloser, error) {
-	return nil, errors.New("unsupported")
+	_, found := c.c.images[c.ref.String()]
+	if !found {
+		return nil, fmt.Errorf("no image found with ref: %s", c.ref.String())
+	}
+	b := make([]byte, 256)
+	rand.Read(b)
+	return io.NopCloser(bytes.NewReader(b)), nil
 }
 func (c cacheMockerSource) Descriptor() *registry.Descriptor {
 	return c.descriptor
@@ -281,14 +290,8 @@ func (c cacheMockerSource) Descriptor() *registry.Descriptor {
 
 func TestBuild(t *testing.T) {
 	var (
-		nonLocal string
 		cacheDir = "somecachedir"
 	)
-	if runtime.GOARCH == "amd64" {
-		nonLocal = "arm64"
-	} else {
-		nonLocal = "amd64"
-	}
 	tests := []struct {
 		msg     string
 		p       Pkg
@@ -302,7 +305,7 @@ func TestBuild(t *testing.T) {
 		{"not at head", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64"}, commitHash: "foo"}, nil, []string{"amd64"}, &dockerMocker{supportContexts: false}, &cacheMocker{}, "Cannot build from commit hash != HEAD"},
 		{"no build cache", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64"}, commitHash: "HEAD"}, nil, []string{"amd64"}, &dockerMocker{supportContexts: false}, &cacheMocker{}, "must provide linuxkit build cache"},
 		{"unsupported contexts", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir)}, []string{"amd64"}, &dockerMocker{supportContexts: false}, &cacheMocker{}, "contexts not supported, check docker version"},
-		{"load docker without local platform", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64", "arm64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir), WithBuildTargetDockerCache()}, []string{nonLocal}, &dockerMocker{supportContexts: false}, &cacheMocker{}, "must build for local platform"},
+		{"load docker without local platform", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64", "arm64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir), WithBuildTargetDockerCache()}, []string{"amd64", "arm64"}, &dockerMocker{supportContexts: true, enableBuild: true, images: map[string][]byte{}, enableTag: true}, &cacheMocker{enableImagePull: false, enableImageLoad: true, enableIndexWrite: true}, ""},
 		{"amd64", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64", "arm64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir)}, []string{"amd64"}, &dockerMocker{supportContexts: true, enableBuild: true}, &cacheMocker{enableImagePull: false, enableImageLoad: true, enableIndexWrite: true}, ""},
 		{"arm64", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64", "arm64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir)}, []string{"arm64"}, &dockerMocker{supportContexts: true, enableBuild: true}, &cacheMocker{enableImagePull: false, enableImageLoad: true, enableIndexWrite: true}, ""},
 		{"amd64 and arm64", Pkg{org: "foo", image: "bar", hash: "abc", arches: []string{"amd64", "arm64"}, commitHash: "HEAD"}, []BuildOpt{WithBuildCacheDir(cacheDir)}, []string{"amd64", "arm64"}, &dockerMocker{supportContexts: true, enableBuild: true}, &cacheMocker{enableImagePull: false, enableImageLoad: true, enableIndexWrite: true}, ""},

src/cmd/linuxkit/pkglib/docker.go

@@ -288,7 +288,7 @@ func (dr *dockerRunnerImpl) builderEnsureContainer(ctx context.Context, name, im
 	}
 	// create the builder
 	args := []string{"container", "run", "-d", "--name", name, "--privileged", image, "--allow-insecure-entitlement", "network.host", "--addr", fmt.Sprintf("unix://%s", buildkitSocketPath), "--debug"}
-	msg := fmt.Sprintf("creating builder container '%s' in context '%s", name, dockerContext)
+	msg := fmt.Sprintf("creating builder container '%s' in context '%s'", name, dockerContext)
 	fmt.Println(msg)
 	if err := dr.command(nil, ioutil.Discard, ioutil.Discard, args...); err != nil {
 		return nil, err