| /** |
| * 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.hdfs.server.datanode; |
| |
| import java.io.IOException; |
| import java.util.List; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.hdfs.server.datanode.FSDataset.FSVolume; |
| |
| /************************************************** |
| * BlockVolumeChoosingPolicy allows a DataNode to |
| * specify what policy is to be used while choosing |
| * a volume for a block request. |
| * |
| ***************************************************/ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public interface BlockVolumeChoosingPolicy { |
| |
| /** |
| * Returns a specific FSVolume after applying a suitable choice algorithm |
| * to place a given block, given a list of FSVolumes and the block |
| * size sought for storage. |
| * |
| * (Policies that maintain state must be thread-safe.) |
| * |
| * @param volumes - the array of FSVolumes that are available. |
| * @param blockSize - the size of the block for which a volume is sought. |
| * @return the chosen volume to store the block. |
| * @throws IOException when disks are unavailable or are full. |
| */ |
| public FSVolume chooseVolume(List<FSVolume> volumes, long blockSize) |
| throws IOException; |
| |
| } |