hadoop BlockResolver 源码
haddop BlockResolver 代码
文件路径：/hadoop-tools/hadoop-fs2img/src/main/java/org/apache/hadoop/hdfs/server/namenode/BlockResolver.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.util.ArrayList;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.BlockProto;
/**
* Given an external reference, create a sequence of blocks and associated
* metadata.
*/
@InterfaceAudience.Public
@InterfaceStability.Unstable
public abstract class BlockResolver {
protected BlockProto buildBlock(long blockId, long bytes) {
return buildBlock(blockId, bytes, 1001);
}
protected BlockProto buildBlock(long blockId, long bytes, long genstamp) {
BlockProto.Builder b = BlockProto.newBuilder()
.setBlockId(blockId)
.setNumBytes(bytes)
.setGenStamp(genstamp);
return b.build();
}
/**
* @param s the external reference.
* @return sequence of blocks that make up the reference.
*/
public Iterable<BlockProto> resolve(FileStatus s) {
List<Long> lengths = blockLengths(s);
ArrayList<BlockProto> ret = new ArrayList<>(lengths.size());
long tot = 0;
for (long l : lengths) {
tot += l;
ret.add(buildBlock(nextId(), l));
}
if (tot != s.getLen()) {
// log a warning?
throw new IllegalStateException(
"Expected " + s.getLen() + " found " + tot);
}
return ret;
}
/**
* @return the next block id.
*/
public abstract long nextId();
/**
* @return the maximum sequentially allocated block ID for this filesystem.
*/
protected abstract long lastId();
/**
* @param status the external reference.
* @return the lengths of the resultant blocks.
*/
protected abstract List<Long> blockLengths(FileStatus status);
/**
* @param status the external reference.
* @return the block size to assign to this external reference.
*/
public long preferredBlockSize(FileStatus status) {
return status.getBlockSize();
}
/**
* @param status the external reference.
* @return the replication to assign to this external reference.
*/
public abstract int getReplication(FileStatus status);
}
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