Refactor: use variadic parameter instead of new function name

Use NewChunkGroup with optional concurrentReaders parameter instead of
creating a separate NewChunkGroupWithConcurrency function.

This maintains backward compatibility - existing callers without the
parameter get the default of 16 concurrent readers.

weed/filer/filechunk_group.go

@@ -20,23 +20,19 @@ type ChunkGroup struct {
 	concurrentReaders int
 }
 
-// NewChunkGroup creates a ChunkGroup with default concurrency settings.
-// For better read performance, use NewChunkGroupWithConcurrency instead.
-func NewChunkGroup(lookupFn wdclient.LookupFileIdFunctionType, chunkCache chunk_cache.ChunkCache, chunks []*filer_pb.FileChunk) (*ChunkGroup, error) {
-	return NewChunkGroupWithConcurrency(lookupFn, chunkCache, chunks, 16)
-}
-
-// NewChunkGroupWithConcurrency creates a ChunkGroup with configurable concurrency.
+// NewChunkGroup creates a ChunkGroup with configurable concurrency.
+// concurrentReaders is optional; if not provided or <= 0, defaults to 16.
 // concurrentReaders controls:
 // - Maximum parallel chunk fetches during read operations
 // - Read-ahead prefetch parallelism
 // - Number of concurrent section reads for large files
-func NewChunkGroupWithConcurrency(lookupFn wdclient.LookupFileIdFunctionType, chunkCache chunk_cache.ChunkCache, chunks []*filer_pb.FileChunk, concurrentReaders int) (*ChunkGroup, error) {
-	if concurrentReaders <= 0 {
-		concurrentReaders = 16
+func NewChunkGroup(lookupFn wdclient.LookupFileIdFunctionType, chunkCache chunk_cache.ChunkCache, chunks []*filer_pb.FileChunk, concurrentReaders ...int) (*ChunkGroup, error) {
+	readers := 16
+	if len(concurrentReaders) > 0 && concurrentReaders[0] > 0 {
+		readers = concurrentReaders[0]
 	}
 	// ReaderCache limit should be at least concurrentReaders to allow parallel prefetching
-	readerCacheLimit := concurrentReaders * 2
+	readerCacheLimit := readers * 2
 	if readerCacheLimit < 32 {
 		readerCacheLimit = 32
 	}
@@ -44,7 +40,7 @@ func NewChunkGroupWithConcurrency(lookupFn wdclient.LookupFileIdFunctionType, ch
 		lookupFn:          lookupFn,
 		sections:          make(map[SectionIndex]*FileChunkSection),
 		readerCache:       NewReaderCache(readerCacheLimit, chunkCache, lookupFn),
-		concurrentReaders: concurrentReaders,
+		concurrentReaders: readers,
 	}
 
 	err := group.SetChunks(chunks)

weed/mount/filehandle.go

@@ -81,7 +81,7 @@ func (fh *FileHandle) SetEntry(entry *filer_pb.Entry) {
 		fileSize := filer.FileSize(entry)
 		entry.Attributes.FileSize = fileSize
 		var resolveManifestErr error
-		fh.entryChunkGroup, resolveManifestErr = filer.NewChunkGroupWithConcurrency(fh.wfs.LookupFn(), fh.wfs.chunkCache, entry.Chunks, fh.wfs.option.ConcurrentReaders)
+		fh.entryChunkGroup, resolveManifestErr = filer.NewChunkGroup(fh.wfs.LookupFn(), fh.wfs.chunkCache, entry.Chunks, fh.wfs.option.ConcurrentReaders)
 		if resolveManifestErr != nil {
 			glog.Warningf("failed to resolve manifest chunks in %+v", entry)
 		}