hadoop ClientMmap 源码
haddop ClientMmap 代码
文件路径：/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ClientMmap.java
/**
* 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.shortcircuit;
import org.apache.hadoop.classification.InterfaceAudience;
import java.io.Closeable;
import java.nio.MappedByteBuffer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A reference to a memory-mapped region used by an HDFS client.
*/
@InterfaceAudience.Private
public class ClientMmap implements Closeable {
static final Logger LOG = LoggerFactory.getLogger(ClientMmap.class);
/**
* A reference to the block replica which this mmap relates to.
*/
private ShortCircuitReplica replica;
/**
* The java ByteBuffer object.
*/
private final MappedByteBuffer map;
/**
* Whether or not this ClientMmap anchors the replica into memory while
* it exists. Closing an anchored ClientMmap unanchors the replica.
*/
private final boolean anchored;
ClientMmap(ShortCircuitReplica replica, MappedByteBuffer map,
boolean anchored) {
this.replica = replica;
this.map = map;
this.anchored = anchored;
}
/**
* Close the ClientMmap object.
*/
@Override
public void close() {
if (replica != null) {
if (anchored) {
replica.removeNoChecksumAnchor();
}
replica.unref();
}
replica = null;
}
public MappedByteBuffer getMappedByteBuffer() {
return map;
}
}
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