filer.sync: show active chunk transfers when sync progress stalls

When the sync watermark is not advancing, print each in-progress chunk
transfer with its file path, bytes received so far, and current status
(downloading, uploading, or waiting with backoff duration). This helps
diagnose which files are blocking progress during replication.

Closes #8542

weed/command/filer_sync.go

@@ -359,6 +359,7 @@ func doSubscribeFilerMetaChanges(clientId int32, clientEpoch int32, sourceGrpcDi
 	}
 
 	var lastLogTsNs = time.Now().UnixNano()
+	var lastProgressedTsNs int64
 	var clientName = fmt.Sprintf("syncFrom_%s_To_%s", string(sourceFiler), string(targetFiler))
 	processEventFnWithOffset := pb.AddOffsetFunc(func(resp *filer_pb.SubscribeMetadataResponse) error {
 		processor.AddSyncJob(resp)
@@ -372,6 +373,13 @@ func doSubscribeFilerMetaChanges(clientId int32, clientEpoch int32, sourceGrpcDi
 		now := time.Now().UnixNano()
 		glog.V(0).Infof("sync %s to %s progressed to %v %0.2f/sec", sourceFiler, targetFiler, time.Unix(0, offsetTsNs), float64(counter)/(float64(now-lastLogTsNs)/1e9))
 		lastLogTsNs = now
+		if offsetTsNs == lastProgressedTsNs {
+			for _, t := range filerSink.ActiveTransfers() {
+				glog.V(0).Infof("  %s %s: %d bytes received, %s",
+					t.ChunkFileId, t.Path, t.BytesReceived, t.Status)
+			}
+		}
+		lastProgressedTsNs = offsetTsNs
 		// collect synchronous offset
 		statsCollect.FilerSyncOffsetGauge.WithLabelValues(sourceFiler.String(), targetFiler.String(), clientName, sourcePath).Set(float64(offsetTsNs))
 		return setOffset(targetGrpcDialOption, targetFiler, getSignaturePrefixByPath(sourcePath), sourceFilerSignature, offsetTsNs)