add flatten

cmd/flatten/main.go

@@ -0,0 +1,129 @@
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/empty"
+	"github.com/google/go-containerregistry/pkg/v1/mutate"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/tarball"
+	"github.com/imjasonh/kontain.me/pkg/serve"
+)
+
+func main() {
+	http.Handle("/v2/", &server{
+		info:  log.New(os.Stdout, "I ", log.Ldate|log.Ltime|log.Lshortfile),
+		error: log.New(os.Stderr, "E ", log.Ldate|log.Ltime|log.Lshortfile),
+	})
+	http.Handle("/", http.RedirectHandler("https://kontain.me", http.StatusMovedPermanently))
+
+	log.Println("Starting...")
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "8080"
+		log.Printf("Defaulting to port %s", port)
+	}
+	log.Printf("Listening on port %s", port)
+	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
+}
+
+type server struct {
+	info, error *log.Logger
+}
+
+func (s *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	s.info.Println("handler:", r.Method, r.URL)
+	path := strings.TrimPrefix(r.URL.String(), "/v2/")
+
+	switch {
+	case path == "":
+		// API Version check.
+		w.Header().Set("Docker-Distribution-API-Version", "registry/2.0")
+		return
+	case strings.Contains(path, "/blobs/"),
+		strings.Contains(path, "/manifests/sha256:"):
+		// Extract requested blob digest and redirect to serve it from GCS.
+		// If it doesn't exist, this will return 404.
+		parts := strings.Split(r.URL.Path, "/")
+		digest := parts[len(parts)-1]
+		serve.Blob(w, r, digest)
+	case strings.Contains(path, "/manifests/"):
+		s.serveMirrorManifest(w, r)
+	default:
+		serve.Error(w, serve.ErrNotFound)
+	}
+}
+
+// mirror.kontain.me/ubuntu -> mirror ubuntu and serve
+func (s *server) serveMirrorManifest(w http.ResponseWriter, r *http.Request) {
+	path := strings.TrimPrefix(r.URL.Path, "/v2/")
+	parts := strings.Split(path, "/")
+
+	refstr := strings.Join(parts[:len(parts)-2], "/")
+	tagOrDigest := parts[len(parts)-1]
+	if strings.HasPrefix(tagOrDigest, "sha256:") {
+		refstr += "@" + tagOrDigest
+	} else {
+		refstr += ":" + tagOrDigest
+	}
+	for strings.HasPrefix(refstr, "flatten.kontain.me/") {
+		refstr = strings.TrimPrefix(refstr, "flatten.kontain.me/")
+	}
+
+	ref, err := name.ParseReference(refstr)
+	if err != nil {
+		s.error.Printf("ERROR (ParseReference(%q)): %v", refstr, err)
+		serve.Error(w, err)
+		return
+	}
+
+	// TODO: remote.Head(ref) and check for blobs/{digest}-flattened to
+	// serve that instead.
+	// TODO: support manifest lists.
+
+	img, err := remote.Image(ref)
+	if err != nil {
+		s.error.Printf("ERROR (remote.Image): %v", err)
+		serve.Error(w, err)
+		return
+	}
+
+	l, err := tarball.LayerFromOpener(func() (io.ReadCloser, error) { return mutate.Extract(img), nil })
+	if err != nil {
+		s.error.Printf("ERROR (tarball.LayerFromOpener): %v", err)
+		serve.Error(w, err)
+		return
+	}
+	fimg, err := mutate.AppendLayers(empty.Image, l)
+	if err != nil {
+		s.error.Printf("ERROR (mutate.AppendLayers): %v", err)
+		serve.Error(w, err)
+		return
+	}
+
+	if err := serve.Manifest(w, r, fimg); err != nil {
+		s.error.Printf("ERROR (serve.Manifest): %v", err)
+		serve.Error(w, err)
+		return
+	}
+}