resources/images: Make the image cache more robust

Also allow timeout to be set as a duration string, e.g. `30s`.

Fixes #6501

resources/image.go

@@ -88,7 +88,7 @@ func (i *imageResource) getExif() (*exif.Exif, error) {
 
 		key := i.getImageMetaCacheTargetPath()
 
-		read := func(info filecache.ItemInfo, r io.Reader) error {
+		read := func(info filecache.ItemInfo, r io.ReadSeeker) error {
 			meta := &imageMeta{}
 			data, err := ioutil.ReadAll(r)
 			if err != nil {

resources/image_cache.go

@@ -96,12 +96,18 @@ func (c *imageCache) getOrCreate(
 	// These funcs are protected by a named lock.
 	// read clones the parent to its new name and copies
 	// the content to the destinations.
-	read := func(info filecache.ItemInfo, r io.Reader) error {
+	read := func(info filecache.ItemInfo, r io.ReadSeeker) error {
 		img = parent.clone(nil)
 		rp := img.getResourcePaths()
 		rp.relTargetDirFile.file = relTarget.file
 		img.setSourceFilename(info.Name)
 
+		if err := img.InitConfig(r); err != nil {
+			return err
+		}
+
+		r.Seek(0, 0)
+
 		w, err := img.openDestinationsForWriting()
 		if err != nil {
 			return err
@@ -114,6 +120,7 @@ func (c *imageCache) getOrCreate(
 
 		defer w.Close()
 		_, err = io.Copy(w, r)
+
 		return err
 	}
 

resources/images/image.go

@@ -123,6 +123,15 @@ func (i Image) WithSpec(s Spec) *Image {
 	return &i
 }
 
+// InitConfig reads the image config from the given reader.
+func (i *Image) InitConfig(r io.Reader) error {
+	var err error
+	i.configInit.Do(func() {
+		i.config, _, err = image.DecodeConfig(r)
+	})
+	return err
+}
+
 func (i *Image) initConfig() error {
 	var err error
 	i.configInit.Do(func() {
@@ -130,10 +139,7 @@ func (i *Image) initConfig() error {
 			return
 		}
 
-		var (
-			f      hugio.ReadSeekCloser
-			config image.Config
-		)
+		var f hugio.ReadSeekCloser
 
 		f, err = i.Spec.ReadSeekCloser()
 		if err != nil {
@@ -141,11 +147,7 @@ func (i *Image) initConfig() error {
 		}
 		defer f.Close()
 
-		config, _, err = image.DecodeConfig(f)
-		if err != nil {
-			return
-		}
-		i.config = config
+		i.config, _, err = image.DecodeConfig(f)
 	})
 
 	if err != nil {