| /** |
| * 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.blockmanagement; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.hdfs.protocol.Block; |
| import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager; |
| import org.apache.hadoop.hdfs.server.namenode.INodeId; |
| import org.apache.hadoop.util.SequentialNumber; |
| |
| /** |
| * Generate the next valid block ID by incrementing the maximum block |
| * ID allocated so far, starting at 2^30+1. |
| * |
| * Block IDs used to be allocated randomly in the past. Hence we may |
| * find some conflicts while stepping through the ID space sequentially. |
| * However given the sparsity of the ID space, conflicts should be rare |
| * and can be skipped over when detected. |
| */ |
| @InterfaceAudience.Private |
| public class SequentialBlockIdGenerator extends SequentialNumber { |
| /** |
| * The last reserved block ID. |
| */ |
| public static final long LAST_RESERVED_BLOCK_ID = 1024L * 1024 * 1024; |
| |
| private final BlockManager blockManager; |
| |
| SequentialBlockIdGenerator(BlockManager blockManagerRef) { |
| super(LAST_RESERVED_BLOCK_ID); |
| this.blockManager = blockManagerRef; |
| } |
| |
| @Override // NumberGenerator |
| public long nextValue() { |
| Block b = new Block(super.nextValue()); |
| |
| // There may be an occasional conflict with randomly generated |
| // block IDs. Skip over the conflicts. |
| while(isValidBlock(b)) { |
| b.setBlockId(super.nextValue()); |
| } |
| return b.getBlockId(); |
| } |
| |
| /** |
| * Returns whether the given block is one pointed-to by a file. |
| */ |
| private boolean isValidBlock(Block b) { |
| BlockInfo bi = blockManager.getStoredBlock(b); |
| return bi != null && bi.getBlockCollectionId() != |
| INodeId.INVALID_INODE_ID; |
| } |
| } |