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/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{