/**
* 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.FSDatasetInterface.FSVolumeInterface;
/**************************************************
* BlockVolumeChoosingPolicy allows a DataNode to
* specify what policy is to be used while choosing
* a volume for a block request.
*
* Note: This is an evolving i/f and is only for
* advanced use.
*
***************************************************/
@InterfaceAudience.Private
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 FSVolumeInterface chooseVolume(List<FSVolumeInterface> volumes, long blockSize)
throws IOException;
}