hadoop NullBlockAliasMap 源码
haddop NullBlockAliasMap 代码
文件路径：/hadoop-tools/hadoop-fs2img/src/main/java/org/apache/hadoop/hdfs/server/namenode/NullBlockAliasMap.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.server.namenode;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Optional;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.server.common.FileRegion;
import org.apache.hadoop.hdfs.server.common.blockaliasmap.BlockAliasMap;
/**
* Null sink for region information emitted from FSImage.
*/
@InterfaceAudience.Public
@InterfaceStability.Unstable
public class NullBlockAliasMap extends BlockAliasMap<FileRegion> {
@Override
public Reader<FileRegion> getReader(Reader.Options opts, String blockPoolID)
throws IOException {
return new Reader<FileRegion>() {
@Override
public Iterator<FileRegion> iterator() {
return new Iterator<FileRegion>() {
@Override
public boolean hasNext() {
return false;
}
@Override
public FileRegion next() {
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override
public void close() throws IOException {
// do nothing
}
@Override
public Optional<FileRegion> resolve(Block ident) throws IOException {
throw new UnsupportedOperationException();
}
};
}
@Override
public Writer getWriter(Writer.Options opts, String blockPoolID)
throws IOException {
return new Writer<FileRegion>() {
@Override
public void store(FileRegion token) throws IOException {
// do nothing
}
@Override
public void close() throws IOException {
// do nothing
}
};
}
@Override
public void refresh() throws IOException {
// do nothing
}
@Override
public void close() throws IOException {
}
}
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