Add volume id lookup caching

go/operation/lookup_vid_cache.go

@@ -0,0 +1,41 @@
+package operation
+
+import (
+	"errors"
+	"strconv"
+	"time"
+)
+
+type VidInfo struct {
+	Locations       []Location
+	NextRefreshTime time.Time
+}
+type VidCache struct {
+	cache []VidInfo
+}
+
+func (vc *VidCache) Get(vid string) ([]Location, error) {
+	id, _ := strconv.Atoi(vid)
+	if 0 < id && id <= len(vc.cache) {
+		if vc.cache[id-1].Locations == nil {
+			return nil, errors.New("Not Set")
+		}
+		if vc.cache[id-1].NextRefreshTime.Before(time.Now()) {
+			return nil, errors.New("Expired")
+		}
+		return vc.cache[id-1].Locations, nil
+	}
+	return nil, errors.New("Not Found")
+}
+func (vc *VidCache) Set(vid string, locations []Location, duration time.Duration) {
+	id, _ := strconv.Atoi(vid)
+	if id >= len(vc.cache) {
+		for i := id - len(vc.cache); i > 0; i-- {
+			vc.cache = append(vc.cache, VidInfo{})
+		}
+	}
+
+	vc.cache[id-1].Locations = locations
+	vc.cache[id-1].NextRefreshTime = time.Now().Add(duration)
+
+}