/**
* 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.Closeable;
import java.io.IOException;
/**
* This holds volume reference count as AutoClosable resource.
* It increases the reference count by one in the constructor, and decreases
* the reference count by one in {@link #close()}.
*
* <pre>
* {@code
* try (FsVolumeReference ref = volume.obtainReference()) {
* // Do IOs on the volume
* volume.createRwb(...);
* ...
* }
* }
* </pre>
*/
public interface FsVolumeReference extends Closeable {
/**
* Decrease the reference count of the volume.
* @throws IOException it never throws IOException.
*/
@Override
void close() throws IOException;
/**
* Returns the underlying volume object. Return null if the reference was
* released.
*/
FsVolumeSpi getVolume();
}