Add volume id lookup caching

go/operation/lookup.go

@@ -8,6 +8,7 @@ import (
 	"math/rand"
 	"net/url"
 	"strings"
+	"time"
 )
 
 type Location struct {
@@ -20,7 +21,22 @@ type LookupResult struct {
 	Error     string     `json:"error,omitempty"`
 }
 
-func Lookup(server string, vid string) (*LookupResult, error) {
+var (
+	vc VidCache
+)
+
+func Lookup(server string, vid string) (ret *LookupResult, err error) {
+	locations, cache_err := vc.Get(vid)
+	if cache_err != nil {
+		ret, err = do_lookup(server, vid)
+		vc.Set(vid, ret.Locations, 1*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)

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)
+
+}

go/operation/lookup_vid_cache_test.go

@@ -0,0 +1,26 @@
+package operation
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestCaching(t *testing.T) {
+	var (
+		vc VidCache
+	)
+	var locations []Location
+	locations = append(locations, Location{Url: "a.com:8080"})
+	vc.Set("123", locations, time.Second)
+	ret, _ := vc.Get("123")
+	if ret == nil {
+		t.Fatal("Not found vid 123")
+	}
+	fmt.Printf("vid 123 locations = %v\n", ret)
+	time.Sleep(2 * time.Second)
+	ret, _ = vc.Get("123")
+	if ret != nil {
+		t.Fatal("Not found vid 123")
+	}
+}