add logging

weed/filer/filechunk_manifest.go

@@ -110,6 +110,7 @@ func retriedFetchChunkData(urlStrings []string, cipherKey []byte, isGzipped bool
 				break
 			}
 		}
+		glog.V(0).Infof("sleep for %v before retrying reading", waitTime)
 		time.Sleep(waitTime)
 	}