fix(filersink): return lock-free snapshot from ActiveTransfers (#9604)

ChunkTransferStatus embeds a sync.RWMutex, so returning a slice of it
made callers copy the lock when ranging. Split out a copyable
ChunkTransferSnapshot holding the data fields and return that instead.

weed/replication/sink/filersink/fetch_write.go

@@ -242,9 +242,11 @@ func (fs *FilerSink) fetchAndWrite(sourceChunk *filer_pb.FileChunk, path string,
 	}
 
 	transferStatus := &ChunkTransferStatus{
-		ChunkFileId: sourceChunk.GetFileIdString(),
-		Path:        path,
-		Status:      "downloading",
+		ChunkTransferSnapshot: ChunkTransferSnapshot{
+			ChunkFileId: sourceChunk.GetFileIdString(),
+			Path:        path,
+			Status:      "downloading",
+		},
 	}
 	fs.activeTransfers.Store(sourceChunk.GetFileIdString(), transferStatus)
 	defer fs.activeTransfers.Delete(sourceChunk.GetFileIdString())

weed/replication/sink/filersink/filer_sink.go

@@ -22,12 +22,9 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/util"
 )
 
-// ChunkTransferStatus tracks the progress of a single chunk being replicated.
-// Fields are guarded by mu: ChunkFileId and Path are immutable after creation,
-// while BytesReceived, Status, and LastErr are updated by fetchAndWrite and
-// read by ActiveTransfers.
-type ChunkTransferStatus struct {
-	mu            sync.RWMutex
+// ChunkTransferSnapshot is a lock-free, copyable view of a chunk transfer's
+// progress, returned by ActiveTransfers.
+type ChunkTransferSnapshot struct {
 	ChunkFileId   string
 	Path          string
 	BytesReceived int64
@@ -35,6 +32,15 @@ type ChunkTransferStatus struct {
 	LastErr       string
 }
 
+// ChunkTransferStatus tracks the progress of a single chunk being replicated.
+// Fields are guarded by mu: ChunkFileId and Path are immutable after creation,
+// while BytesReceived, Status, and LastErr are updated by fetchAndWrite and
+// read by ActiveTransfers.
+type ChunkTransferStatus struct {
+	mu sync.RWMutex
+	ChunkTransferSnapshot
+}
+
 type FilerSink struct {
 	filerSource       *source.FilerSource
 	grpcAddress       string
@@ -134,18 +140,12 @@ func (fs *FilerSink) SetChunkConcurrency(concurrency int) {
 }
 
 // ActiveTransfers returns an immutable snapshot of all in-progress chunk transfers.
-func (fs *FilerSink) ActiveTransfers() []ChunkTransferStatus {
-	var transfers []ChunkTransferStatus
+func (fs *FilerSink) ActiveTransfers() []ChunkTransferSnapshot {
+	var transfers []ChunkTransferSnapshot
 	fs.activeTransfers.Range(func(key, value any) bool {
 		t := value.(*ChunkTransferStatus)
 		t.mu.RLock()
-		transfers = append(transfers, ChunkTransferStatus{
-			ChunkFileId:   t.ChunkFileId,
-			Path:          t.Path,
-			BytesReceived: t.BytesReceived,
-			Status:        t.Status,
-			LastErr:       t.LastErr,
-		})
+		transfers = append(transfers, t.ChunkTransferSnapshot)
 		t.mu.RUnlock()
 		return true
 	})