Filer: fallback to check master (#7411)

* fallback to check master

* clean up

* parsing

* refactor

* handle parse error

* return error

* avoid dup lookup

* use batch key

* dedup lookup logic

* address comments

* errors.Join(lookupErrors...)

* add a comment

weed/wdclient/masterclient.go

@@ -2,11 +2,17 @@ package wdclient
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/rand"
+	"sort"
+	"strconv"
+	"strings"
 	"sync"
 	"time"
 
+	"golang.org/x/sync/singleflight"
+
 	"github.com/seaweedfs/seaweedfs/weed/util/version"
 
 	"github.com/seaweedfs/seaweedfs/weed/stats"
@@ -29,10 +35,16 @@ type MasterClient struct {
 	masters           pb.ServerDiscovery
 	grpcDialOption    grpc.DialOption
 
+	// TODO: CRITICAL - Data race: resetVidMap() writes to vidMap while other methods read concurrently
+	// This embedded *vidMap should be changed to a private field protected by sync.RWMutex
+	// See: https://github.com/seaweedfs/seaweedfs/issues/[ISSUE_NUMBER]
 	*vidMap
 	vidMapCacheSize  int
 	OnPeerUpdate     func(update *master_pb.ClusterNodeUpdate, startFrom time.Time)
 	OnPeerUpdateLock sync.RWMutex
+
+	// Per-batch in-flight tracking to prevent duplicate lookups for the same set of volumes
+	vidLookupGroup singleflight.Group
 }
 
 func NewMasterClient(grpcDialOption grpc.DialOption, filerGroup string, clientType string, clientHost pb.ServerAddress, clientDataCenter string, rack string, masters pb.ServerDiscovery) *MasterClient {
@@ -59,39 +71,168 @@ func (mc *MasterClient) GetLookupFileIdFunction() LookupFileIdFunctionType {
 }
 
 func (mc *MasterClient) LookupFileIdWithFallback(ctx context.Context, fileId string) (fullUrls []string, err error) {
+	// Try cache first using the fast path
 	fullUrls, err = mc.vidMap.LookupFileId(ctx, fileId)
 	if err == nil && len(fullUrls) > 0 {
 		return
 	}
 
-	err = pb.WithMasterClient(false, mc.GetMaster(ctx), mc.grpcDialOption, false, func(client master_pb.SeaweedClient) error {
-		resp, err := client.LookupVolume(ctx, &master_pb.LookupVolumeRequest{
-			VolumeOrFileIds: []string{fileId},
-		})
-		if err != nil {
-			return fmt.Errorf("LookupVolume %s failed: %v", fileId, err)
+	// Extract volume ID from file ID (format: "volumeId,needle_id_cookie")
+	parts := strings.Split(fileId, ",")
+	if len(parts) != 2 {
+		return nil, fmt.Errorf("invalid fileId %s", fileId)
+	}
+	volumeId := parts[0]
+
+	// Use shared lookup logic with batching and singleflight
+	vidLocations, err := mc.LookupVolumeIdsWithFallback(ctx, []string{volumeId})
+	if err != nil {
+		return nil, fmt.Errorf("LookupVolume %s failed: %v", fileId, err)
+	}
+
+	locations, found := vidLocations[volumeId]
+	if !found || len(locations) == 0 {
+		return nil, fmt.Errorf("volume %s not found for fileId %s", volumeId, fileId)
+	}
+
+	// Build HTTP URLs from locations, preferring same data center
+	var sameDcUrls, otherDcUrls []string
+	for _, loc := range locations {
+		httpUrl := "http://" + loc.Url + "/" + fileId
+		if mc.DataCenter != "" && mc.DataCenter == loc.DataCenter {
+			sameDcUrls = append(sameDcUrls, httpUrl)
+		} else {
+			otherDcUrls = append(otherDcUrls, httpUrl)
 		}
-		for vid, vidLocation := range resp.VolumeIdLocations {
-			for _, vidLoc := range vidLocation.Locations {
-				loc := Location{
-					Url:        vidLoc.Url,
-					PublicUrl:  vidLoc.PublicUrl,
-					GrpcPort:   int(vidLoc.GrpcPort),
-					DataCenter: vidLoc.DataCenter,
-				}
-				mc.vidMap.addLocation(uint32(vid), loc)
-				httpUrl := "http://" + loc.Url + "/" + fileId
-				// Prefer same data center
-				if mc.DataCenter != "" && mc.DataCenter == loc.DataCenter {
-					fullUrls = append([]string{httpUrl}, fullUrls...)
-				} else {
-					fullUrls = append(fullUrls, httpUrl)
-				}
+	}
+
+	// Prefer same data center
+	fullUrls = append(sameDcUrls, otherDcUrls...)
+	return fullUrls, nil
+}
+
+// LookupVolumeIdsWithFallback looks up volume locations, querying master if not in cache
+// Uses singleflight to coalesce concurrent requests for the same batch of volumes
+func (mc *MasterClient) LookupVolumeIdsWithFallback(ctx context.Context, volumeIds []string) (map[string][]Location, error) {
+	result := make(map[string][]Location)
+	var needsLookup []string
+	var lookupErrors []error
+
+	// Check cache first and parse volume IDs once
+	vidStringToUint := make(map[string]uint32, len(volumeIds))
+	for _, vidString := range volumeIds {
+		vid, err := strconv.ParseUint(vidString, 10, 32)
+		if err != nil {
+			return nil, fmt.Errorf("invalid volume id %s: %v", vidString, err)
+		}
+		vidStringToUint[vidString] = uint32(vid)
+
+		locations, found := mc.GetLocations(uint32(vid))
+		if found && len(locations) > 0 {
+			result[vidString] = locations
+		} else {
+			needsLookup = append(needsLookup, vidString)
+		}
+	}
+
+	if len(needsLookup) == 0 {
+		return result, nil
+	}
+
+	// Batch query all missing volumes using singleflight on the batch key
+	// Sort for stable key to coalesce identical batches
+	sort.Strings(needsLookup)
+	batchKey := strings.Join(needsLookup, ",")
+
+	sfResult, err, _ := mc.vidLookupGroup.Do(batchKey, func() (interface{}, error) {
+		// Double-check cache for volumes that might have been populated while waiting
+		stillNeedLookup := make([]string, 0, len(needsLookup))
+		batchResult := make(map[string][]Location)
+
+		for _, vidString := range needsLookup {
+			vid := vidStringToUint[vidString] // Use pre-parsed value
+			if locations, found := mc.GetLocations(vid); found && len(locations) > 0 {
+				batchResult[vidString] = locations
+			} else {
+				stillNeedLookup = append(stillNeedLookup, vidString)
 			}
 		}
-		return nil
+
+		if len(stillNeedLookup) == 0 {
+			return batchResult, nil
+		}
+
+		// Query master with batched volume IDs
+		glog.V(2).Infof("Looking up %d volumes from master: %v", len(stillNeedLookup), stillNeedLookup)
+
+		err := pb.WithMasterClient(false, mc.GetMaster(ctx), mc.grpcDialOption, false, func(client master_pb.SeaweedClient) error {
+			resp, err := client.LookupVolume(ctx, &master_pb.LookupVolumeRequest{
+				VolumeOrFileIds: stillNeedLookup,
+			})
+			if err != nil {
+				return fmt.Errorf("master lookup failed: %v", err)
+			}
+
+			for _, vidLoc := range resp.VolumeIdLocations {
+				if vidLoc.Error != "" {
+					glog.V(0).Infof("volume %s lookup error: %s", vidLoc.VolumeOrFileId, vidLoc.Error)
+					continue
+				}
+
+				// Parse volume ID from response
+				parts := strings.Split(vidLoc.VolumeOrFileId, ",")
+				vidOnly := parts[0]
+				vid, err := strconv.ParseUint(vidOnly, 10, 32)
+				if err != nil {
+					glog.Warningf("Failed to parse volume id '%s' from master response '%s': %v", vidOnly, vidLoc.VolumeOrFileId, err)
+					continue
+				}
+
+				var locations []Location
+				for _, masterLoc := range vidLoc.Locations {
+					loc := Location{
+						Url:        masterLoc.Url,
+						PublicUrl:  masterLoc.PublicUrl,
+						GrpcPort:   int(masterLoc.GrpcPort),
+						DataCenter: masterLoc.DataCenter,
+					}
+					mc.vidMap.addLocation(uint32(vid), loc)
+					locations = append(locations, loc)
+				}
+
+				if len(locations) > 0 {
+					batchResult[vidOnly] = locations
+				}
+			}
+			return nil
+		})
+
+		if err != nil {
+			return batchResult, err
+		}
+		return batchResult, nil
 	})
-	return
+
+	if err != nil {
+		lookupErrors = append(lookupErrors, err)
+	}
+
+	// Merge singleflight batch results
+	if batchLocations, ok := sfResult.(map[string][]Location); ok {
+		for vid, locs := range batchLocations {
+			result[vid] = locs
+		}
+	}
+
+	// Check for volumes that still weren't found
+	for _, vidString := range needsLookup {
+		if _, found := result[vidString]; !found {
+			lookupErrors = append(lookupErrors, fmt.Errorf("volume %s not found", vidString))
+		}
+	}
+
+	// Return aggregated errors using errors.Join to preserve error types
+	return result, errors.Join(lookupErrors...)
 }
 
 func (mc *MasterClient) getCurrentMaster() pb.ServerAddress {