| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.hadoop.fs.statistics; |
| |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * A source of IO statistics. |
| * <p> |
| * These statistics MUST be instance specific, not thread local. |
| * </p> |
| */ |
| |
| @InterfaceStability.Unstable |
| public interface IOStatisticsSource { |
| |
| /** |
| * Return a statistics instance. |
| * <p> |
| * It is not a requirement that the same instance is returned every time. |
| * {@link IOStatisticsSource}. |
| * <p> |
| * If the object implementing this is Closeable, this method |
| * may return null if invoked on a closed object, even if |
| * it returns a valid instance when called earlier. |
| * @return an IOStatistics instance or null |
| */ |
| default IOStatistics getIOStatistics() { |
| return null; |
| } |
| } |
