Simplify ReadFileStream closer, make sure to flush all HTTP responses (#7374)

cmd/storage-rest-server.go

@@ -47,6 +47,7 @@ type storageRESTServer struct {
 func (s *storageRESTServer) writeErrorResponse(w http.ResponseWriter, err error) {
 	w.WriteHeader(http.StatusForbidden)
 	w.Write([]byte(err.Error()))
+	w.(http.Flusher).Flush()
 }
 
 // Authenticates storage client's requests and validates for skewed time.
@@ -93,6 +94,7 @@ func (s *storageRESTServer) GetInstanceID(w http.ResponseWriter, r *http.Request
 	}
 	w.Header().Set("Content-Length", strconv.Itoa(len(s.instanceID)))
 	w.Write([]byte(s.instanceID))
+	w.(http.Flusher).Flush()
 }
 
 // DiskInfoHandler - returns disk info.
@@ -268,6 +270,7 @@ func (s *storageRESTServer) ReadAllHandler(w http.ResponseWriter, r *http.Reques
 	}
 	w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
 	w.Write(buf)
+	w.(http.Flusher).Flush()
 }
 
 // ReadFileHandler - read section of a file.
@@ -311,6 +314,7 @@ func (s *storageRESTServer) ReadFileHandler(w http.ResponseWriter, r *http.Reque
 	}
 	w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
 	w.Write(buf)
+	w.(http.Flusher).Flush()
 }
 
 // ReadFileHandler - read section of a file.
@@ -331,6 +335,7 @@ func (s *storageRESTServer) ReadFileStreamHandler(w http.ResponseWriter, r *http
 		s.writeErrorResponse(w, err)
 		return
 	}
+
 	rc, err := s.storage.ReadFileStream(volume, filePath, int64(offset), int64(length))
 	if err != nil {
 		s.writeErrorResponse(w, err)
@@ -338,7 +343,9 @@ func (s *storageRESTServer) ReadFileStreamHandler(w http.ResponseWriter, r *http
 	}
 	defer rc.Close()
 	w.Header().Set("Content-Length", strconv.Itoa(length))
+
 	io.Copy(w, rc)
+	w.(http.Flusher).Flush()
 }
 
 // ListDirHandler - list a directory.