Solve the problem that `LookupFileId` lookup urls is empty due to leader switching

The vidMap structure is modified to a linked list structure (the length is limited to 5). When the vidMap is reset, the current vidMap is added to the new vidMap as a cache node. When the query locations is empty, the cache node is searched to avoid problems when the master switches leaders.

weed/wdclient/masterclient.go

@@ -23,18 +23,20 @@ type MasterClient struct {
 	grpcDialOption grpc.DialOption
 
 	vidMap
+	vidMapCacheSize int
 
 	OnPeerUpdate func(update *master_pb.ClusterNodeUpdate, startFrom time.Time)
 }
 
 func NewMasterClient(grpcDialOption grpc.DialOption, filerGroup string, clientType string, clientHost pb.ServerAddress, clientDataCenter string, masters map[string]pb.ServerAddress) *MasterClient {
 	return &MasterClient{
-		FilerGroup:     filerGroup,
-		clientType:     clientType,
-		clientHost:     clientHost,
-		masters:        masters,
-		grpcDialOption: grpcDialOption,
-		vidMap:         newVidMap(clientDataCenter),
+		FilerGroup:      filerGroup,
+		clientType:      clientType,
+		clientHost:      clientHost,
+		masters:         masters,
+		grpcDialOption:  grpcDialOption,
+		vidMap:          newVidMap(clientDataCenter),
+		vidMapCacheSize: 5,
 	}
 }
 
@@ -175,10 +177,12 @@ func (mc *MasterClient) tryConnectToMaster(master pb.ServerAddress) (nextHintedL
 				stats.MasterClientConnectCounter.WithLabelValues(stats.RedirectedToleader).Inc()
 				return nil
 			}
-			mc.vidMap = newVidMap("")
+			//mc.vidMap = newVidMap("")
+			mc.resetVidMap()
 			mc.updateVidMap(resp)
 		} else {
-			mc.vidMap = newVidMap("")
+			mc.resetVidMap()
+			//mc.vidMap = newVidMap("")
 		}
 		mc.currentMaster = master
 
@@ -263,3 +267,17 @@ func (mc *MasterClient) WithClient(streamingMode bool, fn func(client master_pb.
 		})
 	})
 }
+
+func (mc *MasterClient) resetVidMap() {
+	tail := &vidMap{vid2Locations: mc.vid2Locations, ecVid2Locations: mc.ecVid2Locations, cache: mc.cache}
+	mc.vidMap = newVidMap("")
+	mc.vidMap.cache = tail
+
+	for i := 0; i < mc.vidMapCacheSize && tail.cache != nil; i++ {
+		if i == mc.vidMapCacheSize-1 {
+			tail.cache = nil
+		} else {
+			tail = tail.cache
+		}
+	}
+}

weed/wdclient/vid_map.go

@@ -40,6 +40,7 @@ type vidMap struct {
 	ecVid2Locations map[uint32][]Location
 	DataCenter      string
 	cursor          int32
+	cache           *vidMap
 }
 
 func newVidMap(dataCenter string) vidMap {
@@ -119,17 +120,29 @@ func (vc *vidMap) GetVidLocations(vid string) (locations []Location, err error)
 }
 
 func (vc *vidMap) GetLocations(vid uint32) (locations []Location, found bool) {
+	glog.V(4).Infof("~ lookup volume id %d: %+v ec:%+v", vid, vc.vid2Locations, vc.ecVid2Locations)
+	locations, found = vc.getLocations(vid)
+	if found && len(locations) > 0 {
+		return locations, found
+	}
+
+	if vc.cache != nil {
+		return vc.cache.GetLocations(vid)
+	}
+
+	return nil, false
+}
+
+func (vc *vidMap) getLocations(vid uint32) (locations []Location, found bool) {
 	vc.RLock()
 	defer vc.RUnlock()
 
-	glog.V(4).Infof("~ lookup volume id %d: %+v ec:%+v", vid, vc.vid2Locations, vc.ecVid2Locations)
-
 	locations, found = vc.vid2Locations[vid]
 	if found && len(locations) > 0 {
 		return
 	}
 	locations, found = vc.ecVid2Locations[vid]
-	return locations, found && len(locations) > 0
+	return
 }
 
 func (vc *vidMap) addLocation(vid uint32, location Location) {
@@ -177,6 +190,10 @@ func (vc *vidMap) addEcLocation(vid uint32, location Location) {
 }
 
 func (vc *vidMap) deleteLocation(vid uint32, location Location) {
+	if vc.cache != nil {
+		vc.cache.deleteLocation(vid, location)
+	}
+
 	vc.Lock()
 	defer vc.Unlock()
 
@@ -193,10 +210,13 @@ func (vc *vidMap) deleteLocation(vid uint32, location Location) {
 			break
 		}
 	}
-
 }
 
 func (vc *vidMap) deleteEcLocation(vid uint32, location Location) {
+	if vc.cache != nil {
+		vc.cache.deleteLocation(vid, location)
+	}
+
 	vc.Lock()
 	defer vc.Unlock()
 
@@ -213,5 +233,4 @@ func (vc *vidMap) deleteEcLocation(vid uint32, location Location) {
 			break
 		}
 	}
-
 }

weed/wdclient/vid_map_test.go

@@ -2,6 +2,8 @@ package wdclient
 
 import (
 	"fmt"
+	"google.golang.org/grpc"
+	"strconv"
 	"testing"
 )
 
@@ -59,6 +61,71 @@ func TestLocationIndex(t *testing.T) {
 	}
 }
 
+func TestLookupFileId(t *testing.T) {
+	mc := NewMasterClient(grpc.EmptyDialOption{}, "", "", "", "", nil)
+	length := 5
+
+	//Construct a cache linked list of length 5
+	for i := 0; i < length; i++ {
+		mc.addLocation(uint32(i), Location{Url: strconv.FormatInt(int64(i), 10)})
+		mc.resetVidMap()
+	}
+	for i := 0; i < length; i++ {
+		locations, found := mc.GetLocations(uint32(i))
+		if !found || len(locations) != 1 || locations[0].Url != strconv.FormatInt(int64(i), 10) {
+			t.Fatalf("urls of vid=%d is not valid.", i)
+		}
+	}
+
+	//When continue to add nodes to the linked list, the previous node will be deleted, and the cache of the response will be gone.
+	for i := length; i < length+5; i++ {
+		mc.addLocation(uint32(i), Location{Url: strconv.FormatInt(int64(i), 10)})
+		mc.resetVidMap()
+	}
+	for i := 0; i < length; i++ {
+		locations, found := mc.GetLocations(uint32(i))
+		if found {
+			t.Fatalf("urls of vid[%d] should not exists, but found: %v", i, locations)
+		}
+	}
+
+	//The delete operation will be applied to all cache nodes
+	_, found := mc.GetLocations(uint32(length))
+	if !found {
+		t.Fatalf("urls of vid[%d] not found", length)
+	}
+
+	//If the locations of the current node exist, return directly
+	newUrl := "abc"
+	mc.addLocation(uint32(length), Location{Url: newUrl})
+	locations, found := mc.GetLocations(uint32(length))
+	if !found || locations[0].Url != newUrl {
+		t.Fatalf("urls of vid[%d] not found", length)
+	}
+
+	//After delete `abc`, cache nodes are searched
+	deleteLoc := Location{Url: newUrl}
+	mc.deleteLocation(uint32(length), deleteLoc)
+	locations, found = mc.GetLocations(uint32(length))
+	if found && locations[0].Url != strconv.FormatInt(int64(length), 10) {
+		t.Fatalf("urls of vid[%d] not expected", length)
+	}
+
+	//lock: concurrent test
+	go func() {
+		for i := 0; i < 100; i++ {
+			mc.addLocation(uint32(i), Location{})
+		}
+	}()
+	for i := 0; i < 10; i++ {
+		for i := 0; i < 100; i++ {
+			for i := 0; i < 20; i++ {
+				_, _ = mc.GetLocations(uint32(i))
+			}
+		}
+	}
+}
+
 func BenchmarkLocationIndex(b *testing.B) {
 	b.SetParallelism(8)
 	vm := vidMap{