read from alternative replica

related to https://github.com/chrislusf/seaweedfs/issues/1512

weed/replication/repl_util/replication_utli.go

@@ -0,0 +1,40 @@
+package repl_util
+
+import (
+	"github.com/chrislusf/seaweedfs/weed/filer"
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/replication/source"
+	"github.com/chrislusf/seaweedfs/weed/util"
+)
+
+func CopyFromChunkViews(chunkViews []*filer.ChunkView, filerSource *source.FilerSource, writeFunc func(data []byte) error) error {
+
+	for _, chunk := range chunkViews {
+
+		fileUrls, err := filerSource.LookupFileId(chunk.FileId)
+		if err != nil {
+			return err
+		}
+
+		var writeErr error
+
+		for _, fileUrl := range fileUrls {
+			err = util.ReadUrlAsStream(fileUrl+"?readDeleted=true", nil, false, chunk.IsFullChunk(), chunk.Offset, int(chunk.Size), func(data []byte) {
+				writeErr = writeFunc(data)
+			})
+			if err != nil {
+				glog.V(1).Infof("read from %s: %v", fileUrl, err)
+			} else if writeErr != nil {
+				glog.V(1).Infof("copy from %s: %v", fileUrl, writeErr)
+			} else {
+				break
+			}
+		}
+
+		if err != nil {
+			return err
+		}
+
+	}
+	return nil
+}