crane: add serve subcommand (#1586)

.golangci.yaml

@@ -14,7 +14,6 @@ issues:
 linters:
   enable:
   - asciicheck
-  - deadcode
   - depguard
   - errorlint
   - gofmt
@@ -28,6 +27,7 @@ linters:
   - tparallel
   - unconvert
   - unparam
+  - unused
   - whitespace
 
   disable:

cmd/crane/cmd/root.go

@@ -94,7 +94,7 @@ func New(use, short string, options []crane.Option) *cobra.Command {
 		},
 	}
 
-	commands := []*cobra.Command{
+	root.AddCommand(
 		NewCmdAppend(&options),
 		NewCmdAuth(options, "crane", "auth"),
 		NewCmdBlob(&options),
@@ -117,9 +117,8 @@ func New(use, short string, options []crane.Option) *cobra.Command {
 		NewCmdTag(&options),
 		NewCmdValidate(&options),
 		NewCmdVersion(),
-	}
-
-	root.AddCommand(commands...)
+		newCmdRegistry(),
+	)
 
 	root.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "Enable debug logs")
 	root.PersistentFlags().BoolVar(&insecure, "insecure", false, "Allow image references to be fetched without TLS")

cmd/crane/cmd/serve.go

@@ -0,0 +1,84 @@
+// Copyright 2023 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 cmd
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	"github.com/google/go-containerregistry/pkg/registry"
+)
+
+func newCmdRegistry() *cobra.Command {
+	cmd := &cobra.Command{
+		Use: "registry",
+	}
+	cmd.AddCommand(newCmdServe())
+	return cmd
+}
+
+func newCmdServe() *cobra.Command {
+	return &cobra.Command{
+		Use:   "serve",
+		Short: "Serve an in-memory registry implementation",
+		Long: `This sub-command serves an in-memory registry implementation on port :8080 (or $PORT)
+
+The command blocks while the server accepts pushes and pulls.
+
+Contents are only stored in memory, and when the process exits, pushed data is lost.`,
+		Args: cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			ctx := cmd.Context()
+
+			port := os.Getenv("PORT")
+			if port == "" {
+				port = "0"
+			}
+			listener, err := net.Listen("tcp", "localhost:"+port)
+			if err != nil {
+				log.Fatalln(err)
+			}
+			porti := listener.Addr().(*net.TCPAddr).Port
+			port = fmt.Sprintf("%d", porti)
+
+			s := &http.Server{
+				ReadHeaderTimeout: 5 * time.Second, // prevent slowloris, quiet linter
+				Handler:           registry.New(),
+			}
+			log.Printf("serving on port %s", port)
+
+			errCh := make(chan error)
+			go func() { errCh <- s.Serve(listener) }()
+
+			<-ctx.Done()
+			log.Println("shutting down...")
+			if err := s.Shutdown(ctx); err != nil {
+				return err
+			}
+
+			if err := <-errCh; !errors.Is(err, http.ErrServerClosed) {
+				return err
+			}
+			return nil
+		},
+	}
+}