org.apache.hadoop.hdfs.server.datanode.fsdataset.VolumeChoosingPolicy Maven / Gradle / Ivy
/**
* 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.fsdataset;
import java.io.IOException;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* This interface specifies the policy for choosing volumes to store replicas.
*/
@InterfaceAudience.Private
public interface VolumeChoosingPolicy {
/**
* Choose a volume to place a replica,
* given a list of volumes and the replica size sought for storage.
*
* The caller should synchronize access to the list of volumes.
*
* @param volumes - a list of available volumes.
* @param replicaSize - the size of the replica for which a volume is sought.
* @param storageId - the storage id of the Volume nominated by the namenode.
* This can usually be ignored by the VolumeChoosingPolicy.
* @return the chosen volume.
* @throws IOException when disks are unavailable or are full.
*/
V chooseVolume(List volumes, long replicaSize, String storageId)
throws IOException;
}