directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/operation/lookup.go

@@ -0,0 +1,118 @@
+package operation
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/rand"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/util"
+)
+
+type Location struct {
+	Url       string `json:"url,omitempty"`
+	PublicUrl string `json:"publicUrl,omitempty"`
+}
+type LookupResult struct {
+	VolumeId  string     `json:"volumeId,omitempty"`
+	Locations []Location `json:"locations,omitempty"`
+	Error     string     `json:"error,omitempty"`
+}
+
+func (lr *LookupResult) String() string {
+	return fmt.Sprintf("VolumeId:%s, Locations:%v, Error:%s", lr.VolumeId, lr.Locations, lr.Error)
+}
+
+var (
+	vc VidCache // caching of volume locations, re-check if after 10 minutes
+)
+
+func Lookup(server string, vid string) (ret *LookupResult, err error) {
+	locations, cache_err := vc.Get(vid)
+	if cache_err != nil {
+		if ret, err = do_lookup(server, vid); err == nil {
+			vc.Set(vid, ret.Locations, 10*time.Minute)
+		}
+	} else {
+		ret = &LookupResult{VolumeId: vid, Locations: locations}
+	}
+	return
+}
+
+func do_lookup(server string, vid string) (*LookupResult, error) {
+	values := make(url.Values)
+	values.Add("volumeId", vid)
+	jsonBlob, err := util.Post("http://"+server+"/dir/lookup", values)
+	if err != nil {
+		return nil, err
+	}
+	var ret LookupResult
+	err = json.Unmarshal(jsonBlob, &ret)
+	if err != nil {
+		return nil, err
+	}
+	if ret.Error != "" {
+		return nil, errors.New(ret.Error)
+	}
+	return &ret, nil
+}
+
+func LookupFileId(server string, fileId string) (fullUrl string, err error) {
+	parts := strings.Split(fileId, ",")
+	if len(parts) != 2 {
+		return "", errors.New("Invalid fileId " + fileId)
+	}
+	lookup, lookupError := Lookup(server, parts[0])
+	if lookupError != nil {
+		return "", lookupError
+	}
+	if len(lookup.Locations) == 0 {
+		return "", errors.New("File Not Found")
+	}
+	return "http://" + lookup.Locations[rand.Intn(len(lookup.Locations))].Url + "/" + fileId, nil
+}
+
+// LookupVolumeIds find volume locations by cache and actual lookup
+func LookupVolumeIds(server string, vids []string) (map[string]LookupResult, error) {
+	ret := make(map[string]LookupResult)
+	var unknown_vids []string
+
+	//check vid cache first
+	for _, vid := range vids {
+		locations, cache_err := vc.Get(vid)
+		if cache_err == nil {
+			ret[vid] = LookupResult{VolumeId: vid, Locations: locations}
+		} else {
+			unknown_vids = append(unknown_vids, vid)
+		}
+	}
+	//return success if all volume ids are known
+	if len(unknown_vids) == 0 {
+		return ret, nil
+	}
+
+	//only query unknown_vids
+	values := make(url.Values)
+	for _, vid := range unknown_vids {
+		values.Add("volumeId", vid)
+	}
+	jsonBlob, err := util.Post("http://"+server+"/vol/lookup", values)
+	if err != nil {
+		return nil, err
+	}
+	err = json.Unmarshal(jsonBlob, &ret)
+	if err != nil {
+		return nil, errors.New(err.Error() + " " + string(jsonBlob))
+	}
+
+	//set newly checked vids to cache
+	for _, vid := range unknown_vids {
+		locations := ret[vid].Locations
+		vc.Set(vid, locations, 10*time.Minute)
+	}
+
+	return ret, nil
+}