Adding Registry Mirror support

This commit aims to add registy mirror support similar to
docker. The UI is similar to docker where user can
provide mirror urls and the image resolves against the provided
mirrors before fetching from default docker regitry mirror url.

Signed-off-by: abhi <abhi@docker.com>

pkg/server/image_pull.go

@@ -25,12 +25,12 @@ import (
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/errdefs"
 	containerdimages "github.com/containerd/containerd/images"
-	"github.com/containerd/containerd/remotes/docker"
 	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 	"k8s.io/kubernetes/pkg/kubelet/apis/cri/v1alpha1/runtime"
 
+	containerdresolver "github.com/containerd/cri-containerd/pkg/containerd/resolver"
 	imagestore "github.com/containerd/cri-containerd/pkg/store/image"
 	"github.com/containerd/cri-containerd/pkg/util"
 )
@@ -83,15 +83,14 @@ func (c *criContainerdService) PullImage(ctx context.Context, r *runtime.PullIma
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse image reference %q: %v", imageRef, err)
 	}
-	// TODO(random-liu): [P0] Avoid concurrent pulling/removing on the same image reference.
 	ref := namedRef.String()
 	if ref != imageRef {
 		logrus.Debugf("PullImage using normalized image ref: %q", ref)
 	}
-
-	resolver := docker.NewResolver(docker.ResolverOptions{
+	resolver := containerdresolver.NewResolver(containerdresolver.Options{
 		Credentials: func(string) (string, string, error) { return ParseAuth(r.GetAuth()) },
 		Client:      http.DefaultClient,
+		Registry:    c.getResolverOptions(),
 	})
 	_, desc, err := resolver.Resolve(ctx, ref)
 	if err != nil {
@@ -212,3 +211,11 @@ func (c *criContainerdService) createImageReference(ctx context.Context, name st
 	_, err = c.client.ImageService().Update(ctx, img, "target")
 	return err
 }
+
+func (c *criContainerdService) getResolverOptions() map[string][]string {
+	options := make(map[string][]string)
+	for ns, mirror := range c.config.Mirrors {
+		options[ns] = append(options[ns], mirror.Endpoints...)
+	}
+	return options
+}