Java tutorial
/** * 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.protocol; import java.io.Serializable; import java.util.Arrays; import java.util.Comparator; import java.util.List; import com.google.common.base.Preconditions; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.fs.StorageType; import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier; import org.apache.hadoop.security.token.Token; import com.google.common.collect.Lists; /** * Associates a block with the Datanodes that contain its replicas * and other block metadata (E.g. the file offset associated with this * block, whether it is corrupt, a location is cached in memory, * security token, etc). */ @InterfaceAudience.Private @InterfaceStability.Evolving public class LocatedBlock { /** * Comparator that ensures that a PROVIDED storage type is greater than any * other storage type. Any other storage types are considered equal. */ private static class ProvidedLastComparator implements Comparator<DatanodeInfoWithStorage>, Serializable { private static final long serialVersionUID = 6441720011443190984L; @Override public int compare(DatanodeInfoWithStorage dns1, DatanodeInfoWithStorage dns2) { if (StorageType.PROVIDED.equals(dns1.getStorageType()) && !StorageType.PROVIDED.equals(dns2.getStorageType())) { return 1; } if (!StorageType.PROVIDED.equals(dns1.getStorageType()) && StorageType.PROVIDED.equals(dns2.getStorageType())) { return -1; } // Storage types of dns1 and dns2 are now both provided or not provided; // thus, are essentially equal for the purpose of this comparator. return 0; } } private final ExtendedBlock b; private long offset; // offset of the first byte of the block in the file private final DatanodeInfoWithStorage[] locs; /** Cached storage ID for each replica */ private final String[] storageIDs; /** Cached storage type for each replica, if reported. */ private final StorageType[] storageTypes; // corrupt flag is true if all of the replicas of a block are corrupt. // else false. If block has few corrupt replicas, they are filtered and // their locations are not part of this object private boolean corrupt; private Token<BlockTokenIdentifier> blockToken = new Token<>(); // use one instance of the Provided comparator as it uses no state. private static ProvidedLastComparator providedLastComparator = new ProvidedLastComparator(); /** * List of cached datanode locations */ private DatanodeInfo[] cachedLocs; // Used when there are no locations static final DatanodeInfoWithStorage[] EMPTY_LOCS = new DatanodeInfoWithStorage[0]; public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs) { // By default, startOffset is unknown(-1) and corrupt is false. this(b, convert(locs, null, null), null, null, -1, false, EMPTY_LOCS); } public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, String[] storageIDs, StorageType[] storageTypes) { this(b, convert(locs, storageIDs, storageTypes), storageIDs, storageTypes, -1, false, EMPTY_LOCS); } public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, String[] storageIDs, StorageType[] storageTypes, long startOffset, boolean corrupt, DatanodeInfo[] cachedLocs) { this(b, convert(locs, storageIDs, storageTypes), storageIDs, storageTypes, startOffset, corrupt, null == cachedLocs || 0 == cachedLocs.length ? EMPTY_LOCS : cachedLocs); } public LocatedBlock(ExtendedBlock b, DatanodeInfoWithStorage[] locs, String[] storageIDs, StorageType[] storageTypes, long startOffset, boolean corrupt, DatanodeInfo[] cachedLocs) { this.b = b; this.offset = startOffset; this.corrupt = corrupt; this.locs = null == locs ? EMPTY_LOCS : locs; this.storageIDs = storageIDs; this.storageTypes = storageTypes; this.cachedLocs = null == cachedLocs || 0 == cachedLocs.length ? EMPTY_LOCS : cachedLocs; } private static DatanodeInfoWithStorage[] convert(DatanodeInfo[] infos, String[] storageIDs, StorageType[] storageTypes) { if (null == infos) { return EMPTY_LOCS; } DatanodeInfoWithStorage[] ret = new DatanodeInfoWithStorage[infos.length]; for (int i = 0; i < infos.length; i++) { ret[i] = new DatanodeInfoWithStorage(infos[i], storageIDs != null ? storageIDs[i] : null, storageTypes != null ? storageTypes[i] : null); } return ret; } public Token<BlockTokenIdentifier> getBlockToken() { return blockToken; } public void setBlockToken(Token<BlockTokenIdentifier> token) { this.blockToken = token; } public ExtendedBlock getBlock() { return b; } /** * Returns the locations associated with this block. The returned array is not * expected to be modified. If it is, caller must immediately invoke * {@link org.apache.hadoop.hdfs.protocol.LocatedBlock#updateCachedStorageInfo} * to update the cached Storage ID/Type arrays. */ public DatanodeInfo[] getLocations() { return locs; } public StorageType[] getStorageTypes() { return storageTypes; } public String[] getStorageIDs() { return storageIDs; } /** * Updates the cached StorageID and StorageType information. Must be * called when the locations array is modified. */ public void updateCachedStorageInfo() { if (storageIDs != null) { for (int i = 0; i < locs.length; i++) { storageIDs[i] = locs[i].getStorageID(); } } if (storageTypes != null) { for (int i = 0; i < locs.length; i++) { storageTypes[i] = locs[i].getStorageType(); } } } /** * Moves all locations that have {@link StorageType} * {@code PROVIDED} to the end of the locations array without * changing the relative ordering of the remaining locations * Only the first {@code activeLen} locations are considered. * The caller must immediately invoke {@link * org.apache.hadoop.hdfs.protocol.LocatedBlock#updateCachedStorageInfo} * to update the cached Storage ID/Type arrays. * @param activeLen */ public void moveProvidedToEnd(int activeLen) { if (activeLen <= 0) { return; } // as this is a stable sort, for elements that are equal, // the current order of the elements is maintained Arrays.sort(locs, 0, (activeLen < locs.length) ? activeLen : locs.length, providedLastComparator); } public long getStartOffset() { return offset; } public long getBlockSize() { return b.getNumBytes(); } public void setStartOffset(long value) { this.offset = value; } public void setCorrupt(boolean corrupt) { this.corrupt = corrupt; } public boolean isCorrupt() { return this.corrupt; } /** * Add a the location of a cached replica of the block. * * @param loc of datanode with the cached replica */ public void addCachedLoc(DatanodeInfo loc) { List<DatanodeInfo> cachedList = Lists.newArrayList(cachedLocs); if (cachedList.contains(loc)) { return; } // Try to re-use a DatanodeInfo already in loc for (DatanodeInfoWithStorage di : locs) { if (loc.equals(di)) { cachedList.add(di); cachedLocs = cachedList.toArray(cachedLocs); return; } } // Not present in loc, add it and go cachedList.add(loc); Preconditions.checkArgument(cachedLocs != EMPTY_LOCS, "Cached locations should only be added when having a backing" + " disk replica!", loc, locs.length, Arrays.toString(locs)); cachedLocs = cachedList.toArray(cachedLocs); } /** * @return Datanodes with a cached block replica */ public DatanodeInfo[] getCachedLocations() { return cachedLocs; } @Override public String toString() { return getClass().getSimpleName() + "{" + b + "; getBlockSize()=" + getBlockSize() + "; corrupt=" + corrupt + "; offset=" + offset + "; locs=" + Arrays.asList(locs) + "}"; } public boolean isStriped() { return false; } public BlockType getBlockType() { return BlockType.CONTIGUOUS; } }