/**
* 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.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
import org.apache.hadoop.util.DiskChecker.DiskOutOfSpaceException;
public class RoundRobinVolumesPolicy implements BlockVolumeChoosingPolicy {
private int curVolume = 0;
@Override
public synchronized FSVolumeInterface chooseVolume(
List<FSVolumeInterface> volumes, long blockSize) throws IOException {
if(volumes.size() < 1) {
throw new DiskOutOfSpaceException("No more available volumes");
}
// since volumes could've been removed because of the failure
// make sure we are not out of bounds
if(curVolume >= volumes.size()) {
curVolume = 0;
}
int startVolume = curVolume;
long maxAvailable = 0;
while (true) {
FSVolumeInterface volume = volumes.get(curVolume);
curVolume = (curVolume + 1) % volumes.size();
long availableVolumeSize = volume.getAvailable();
if (availableVolumeSize > blockSize) { return volume; }
if (availableVolumeSize > maxAvailable) {
maxAvailable = availableVolumeSize;
}
if (curVolume == startVolume) {
throw new DiskOutOfSpaceException(
"Insufficient space for an additional block. Volume with the most available space has "
+ maxAvailable
+ " bytes free, configured block size is "
+ blockSize);
}
}
}
}