diff --git a/assets/common.go b/assets/common.go
index d435c3e..c2c562b 100644
--- a/assets/common.go
+++ b/assets/common.go
@@ -3,15 +3,8 @@ package assets
 import (
 	"XProxy/logger"
 	"io"
-	"time"
 )
 
-type upstream interface {
-	getTag() string
-	doRequest() io.Reader
-	lastModify() time.Time
-}
-
 type asset struct {
 	tag     string
 	stream  io.Reader
diff --git a/assets/update.go b/assets/update.go
index 8adcbca..652344e 100644
--- a/assets/update.go
+++ b/assets/update.go
@@ -44,17 +44,17 @@ func saveAsset(file string, content []byte, date *time.Time) error {
 // save them locally. Local files will be overwritten if they exist.
 func updateRemoteAsset(file string, url string, proxy *urlpkg.URL) error {
 	logger.Debugf("Start downloading remote asset `%s` to `%s`", url, file)
-	asset, date, err := downloadAsset(url, proxy)
-	if err != nil {
-		logger.Errorf("Failed to download remote asset `%s`", url)
-		return err
-	}
+	//asset, date, err := downloadAsset(url, proxy)
+	//if err != nil {
+	//	logger.Errorf("Failed to download remote asset `%s`", url)
+	//	return err
+	//}
 	//if asset, err = tryExtract(asset); err != nil {
 	//	return err
 	//}
-	if err := saveAsset(file, asset, date); err != nil {
-		return err
-	}
+	//if err := saveAsset(file, asset, date); err != nil {
+	//	return err
+	//}
 	logger.Infof("Successfully obtained remote asset `%s`", file)
 	return nil
 }
diff --git a/assets/upstream/local.go b/assets/upstream/local.go
new file mode 100644
index 0000000..b5c8d42
--- /dev/null
+++ b/assets/upstream/local.go
@@ -0,0 +1,36 @@
+package upstream
+
+import (
+	"XProxy/logger"
+	"io"
+	"os"
+	"time"
+)
+
+type localAsset struct {
+	tag  string
+	path string
+}
+
+func (l *localAsset) Tag() string {
+	return l.tag
+}
+
+func (l *localAsset) lastModify() time.Time {
+	stat, err := os.Stat(l.path)
+	if err != nil {
+		logger.Warnf("Failed to get local file stat -> %v", err)
+		return time.Now() // unknown modify time
+	}
+	return stat.ModTime() // using last modify time of src file
+}
+
+func (l *localAsset) Request() (io.ReadCloser, time.Time, error) {
+	logger.Debugf("Start extracting local asset `%s`", l.path)
+	stream, err := os.Open(l.path)
+	if err != nil {
+		logger.Errorf("Failed to read local asset -> %v", err)
+		return nil, l.lastModify(), err
+	}
+	return stream, l.lastModify(), nil
+}
diff --git a/assets/upstream/remote.go b/assets/upstream/remote.go
new file mode 100644
index 0000000..0e9d68b
--- /dev/null
+++ b/assets/upstream/remote.go
@@ -0,0 +1,19 @@
+package upstream
+
+import (
+	"io"
+	"net/http"
+	"time"
+)
+
+type remoteAsset struct {
+	client http.Client
+}
+
+func (r *remoteAsset) GetTag() string {
+	return ""
+}
+
+func (r *remoteAsset) Request() (io.ReadCloser, time.Time, error) {
+	return nil, time.Now(), nil
+}
diff --git a/assets/remote.go b/assets/upstream/remote_legacy.go
similarity index 99%
rename from assets/remote.go
rename to assets/upstream/remote_legacy.go
index b57e9c2..c6f71f7 100644
--- a/assets/remote.go
+++ b/assets/upstream/remote_legacy.go
@@ -1,4 +1,4 @@
-package assets
+package upstream
 
 import (
 	"XProxy/logger"
diff --git a/assets/upstream/upstream.go b/assets/upstream/upstream.go
new file mode 100644
index 0000000..6aec826
--- /dev/null
+++ b/assets/upstream/upstream.go
@@ -0,0 +1,29 @@
+package upstream
+
+import (
+	"io"
+	urlpkg "net/url"
+	"time"
+)
+
+// Upstream interface is an abstraction that supports initiating request and
+// returning information such as data streams.
+type Upstream interface {
+	// Tag function get the description of current upstream.
+	Tag() (tag string)
+
+	// Request function initiates a request, returns the data stream and last
+	// modification time, or an error information.
+	Request() (stream io.ReadCloser, lastModify time.Time, err error)
+}
+
+func NewLocalAsset(tag string, path string) Upstream {
+	return &localAsset{
+		tag:  tag,
+		path: path,
+	}
+}
+
+func NewRemoteAsset(url string, proxy *urlpkg.URL) Upstream {
+	return &remoteAsset{}
+}