config: support multiple storage locations

added support to point multiple storage locations in zot by running multiple instance of zot in background.

see examples/config-multiple.json for more info about config.

Closes #181

pkg/storage/storage.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 
@@ -37,6 +38,11 @@ type BlobUpload struct {
 	ID        string
 }
 
+type StoreController struct {
+	DefaultStore *ImageStore
+	SubStore     map[string]*ImageStore
+}
+
 // ImageStore provides the image storage operations.
 type ImageStore struct {
 	rootDir     string
@@ -48,6 +54,39 @@ type ImageStore struct {
 	log         zerolog.Logger
 }
 
+func (is *ImageStore) RootDir() string {
+	return is.rootDir
+}
+
+func getRoutePrefix(name string) string {
+	names := strings.SplitN(name, "/", 2)
+
+	if len(names) != 2 { // nolint: gomnd
+		// it means route is of global storage e.g "centos:latest"
+		if len(names) == 1 {
+			return "/"
+		}
+	}
+
+	return fmt.Sprintf("/%s", names[0])
+}
+
+func (sc StoreController) GetImageStore(name string) *ImageStore {
+	if sc.SubStore != nil {
+		// SubStore is being provided, now we need to find equivalent image store and this will be found by splitting name
+		prefixName := getRoutePrefix(name)
+
+		imgStore, ok := sc.SubStore[prefixName]
+		if !ok {
+			imgStore = sc.DefaultStore
+		}
+
+		return imgStore
+	}
+
+	return sc.DefaultStore
+}
+
 // NewImageStore returns a new image store backed by a file storage.
 func NewImageStore(rootDir string, gc bool, dedupe bool, log zlog.Logger) *ImageStore {
 	if _, err := os.Stat(rootDir); os.IsNotExist(err) {
@@ -1174,6 +1213,36 @@ func Scrub(dir string, fix bool) error {
 
 // utility routines
 
+func CheckHardLink(srcFileName string, destFileName string) error {
+	return os.Link(srcFileName, destFileName)
+}
+
+func ValidateHardLink(rootDir string) error {
+	err := ioutil.WriteFile(path.Join(rootDir, "hardlinkcheck.txt"), //nolint: gosec
+		[]byte("check whether hardlinks work on filesystem"), 0644)
+	if err != nil {
+		return err
+	}
+
+	err = CheckHardLink(path.Join(rootDir, "hardlinkcheck.txt"), path.Join(rootDir, "duphardlinkcheck.txt"))
+	if err != nil {
+		// Remove hardlinkcheck.txt if hardlink fails
+		zerr := os.RemoveAll(path.Join(rootDir, "hardlinkcheck.txt"))
+		if zerr != nil {
+			return zerr
+		}
+
+		return err
+	}
+
+	err = os.RemoveAll(path.Join(rootDir, "hardlinkcheck.txt"))
+	if err != nil {
+		return err
+	}
+
+	return os.RemoveAll(path.Join(rootDir, "duphardlinkcheck.txt"))
+}
+
 func dirExists(d string) bool {
 	fi, err := os.Stat(d)
 	if err != nil && os.IsNotExist(err) {

pkg/storage/storage_test.go

@@ -598,3 +598,89 @@ func TestNegativeCases(t *testing.T) {
 		So(err, ShouldNotBeNil)
 	})
 }
+
+func TestHardLink(t *testing.T) {
+	Convey("Test if filesystem supports hardlink", t, func() {
+		dir, err := ioutil.TempDir("", "storage-hard-test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(dir)
+
+		err = storage.ValidateHardLink(dir)
+		So(err, ShouldBeNil)
+
+		err = ioutil.WriteFile(path.Join(dir, "hardtest.txt"), []byte("testing hard link code"), 0644) //nolint: gosec
+		if err != nil {
+			panic(err)
+		}
+
+		err = os.Chmod(dir, 0400)
+		if err != nil {
+			panic(err)
+		}
+
+		err = storage.CheckHardLink(path.Join(dir, "hardtest.txt"), path.Join(dir, "duphardtest.txt"))
+		So(err, ShouldNotBeNil)
+
+		err = os.Chmod(dir, 0644)
+		if err != nil {
+			panic(err)
+		}
+	})
+}
+
+func TestStorageHandler(t *testing.T) {
+	Convey("Test storage handler", t, func() {
+		// Create temporary directory
+		firstRootDir, err := ioutil.TempDir("", "util_test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(firstRootDir)
+
+		secondRootDir, err := ioutil.TempDir("", "util_test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(secondRootDir)
+
+		thirdRootDir, err := ioutil.TempDir("", "util_test")
+		if err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(thirdRootDir)
+
+		log := log.NewLogger("debug", "")
+
+		// Create ImageStore
+		firstStore := storage.NewImageStore(firstRootDir, false, false, log)
+
+		secondStore := storage.NewImageStore(secondRootDir, false, false, log)
+
+		thirdStore := storage.NewImageStore(thirdRootDir, false, false, log)
+
+		storeController := storage.StoreController{}
+
+		storeController.DefaultStore = firstStore
+
+		subStore := make(map[string]*storage.ImageStore)
+
+		subStore["/a"] = secondStore
+		subStore["/b"] = thirdStore
+
+		storeController.SubStore = subStore
+
+		is := storeController.GetImageStore("zot-x-test")
+		So(is.RootDir(), ShouldEqual, firstRootDir)
+
+		is = storeController.GetImageStore("a/zot-a-test")
+		So(is.RootDir(), ShouldEqual, secondRootDir)
+
+		is = storeController.GetImageStore("b/zot-b-test")
+		So(is.RootDir(), ShouldEqual, thirdRootDir)
+
+		is = storeController.GetImageStore("c/zot-c-test")
+		So(is.RootDir(), ShouldEqual, firstRootDir)
+	})
+}