for moved volumes, redirect with code 501

weed-fs/src/pkg/operation/lookup.go

@@ -0,0 +1,34 @@
+package operation
+
+import (
+  "encoding/json"
+  "net/url"
+  "pkg/storage"
+  "pkg/util"
+  "fmt"
+)
+
+type Location struct {
+  Url       string "url"
+  PublicUrl string "publicUrl"
+}
+type LookupResult struct {
+  Locations []Location "locations"
+  Error     string "error"
+}
+
+func Lookup(server string, vid storage.VolumeId) (*LookupResult, error) {
+  values := make(url.Values)
+  values.Add("volumeId", vid.String())
+  jsonBlob, err := util.Post("http://"+server+"/dir/lookup", values)
+  fmt.Println("Lookup Result:", string(jsonBlob))
+  if err != nil {
+    return nil, err
+  }
+  var ret LookupResult
+  err = json.Unmarshal(jsonBlob, &ret)
+  if err != nil {
+    return nil, err
+  }
+  return &ret, nil
+}

weed-fs/src/pkg/storage/store.go

@@ -136,6 +136,11 @@ func (s *Store) Read(i VolumeId, n *Needle) (int, error) {
 	return 0, errors.New("Not Found")
 }
 
+func (s *Store) HasVolume(i VolumeId) bool {
+  _, ok := s.volumes[i]
+  return ok
+}
+
 type VolumeLocations struct {
 	Vid       VolumeId
 	Locations []string