/**
* 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.Iterator;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.util.GSet;
import org.apache.hadoop.hdfs.util.LightWeightGSet;
/**
* This class maintains the map from a block to its metadata.
* block's metadata currently includes INode it belongs to and
* the datanodes that store the block.
*/
class BlocksMap {
/**
* Internal class for block metadata.
*/
static class BlockInfo extends Block implements LightWeightGSet.LinkedElement {
private INodeFile inode;
/** For implementing {@link LightWeightGSet.LinkedElement} interface */
private LightWeightGSet.LinkedElement nextLinkedElement;
/**
* This array contains triplets of references.
* For each i-th data-node the block belongs to
* triplets[3*i] is the reference to the DatanodeDescriptor
* and triplets[3*i+1] and triplets[3*i+2] are references
* to the previous and the next blocks, respectively, in the
* list of blocks belonging to this data-node.
*/
private Object[] triplets;
BlockInfo(Block blk, int replication) {
super(blk);
this.triplets = new Object[3*replication];
this.inode = null;
}
INodeFile getINode() {
return inode;
}
void setINode(INodeFile inode) {
this.inode = inode;
}
DatanodeDescriptor getDatanode(int index) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3 < triplets.length : "Index is out of bound";
DatanodeDescriptor node = (DatanodeDescriptor)triplets[index*3];
assert node == null ||
DatanodeDescriptor.class.getName().equals(node.getClass().getName()) :
"DatanodeDescriptor is expected at " + index*3;
return node;
}
BlockInfo getPrevious(int index) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3+1 < triplets.length : "Index is out of bound";
BlockInfo info = (BlockInfo)triplets[index*3+1];
assert info == null ||
BlockInfo.class.getName().equals(info.getClass().getName()) :
"BlockInfo is expected at " + index*3;
return info;
}
BlockInfo getNext(int index) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3+2 < triplets.length : "Index is out of bound";
BlockInfo info = (BlockInfo)triplets[index*3+2];
assert info == null ||
BlockInfo.class.getName().equals(info.getClass().getName()) :
"BlockInfo is expected at " + index*3;
return info;
}
void setDatanode(int index, DatanodeDescriptor node) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3 < triplets.length : "Index is out of bound";
triplets[index*3] = node;
}
void setPrevious(int index, BlockInfo to) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3+1 < triplets.length : "Index is out of bound";
triplets[index*3+1] = to;
}
void setNext(int index, BlockInfo to) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3+2 < triplets.length : "Index is out of bound";
triplets[index*3+2] = to;
}
private int getCapacity() {
assert this.triplets != null : "BlockInfo is not initialized";
assert triplets.length % 3 == 0 : "Malformed BlockInfo";
return triplets.length / 3;
}
/**
* Ensure that there is enough space to include num more triplets.
* * @return first free triplet index.
*/
private int ensureCapacity(int num) {
assert this.triplets != null : "BlockInfo is not initialized";
int last = numNodes();
if(triplets.length >= (last+num)*3)
return last;
/* Not enough space left. Create a new array. Should normally
* happen only when replication is manually increased by the user. */
Object[] old = triplets;
triplets = new Object[(last+num)*3];
for(int i=0; i < last*3; i++) {
triplets[i] = old[i];
}
return last;
}
/**
* Count the number of data-nodes the block belongs to.
*/
int numNodes() {
assert this.triplets != null : "BlockInfo is not initialized";
assert triplets.length % 3 == 0 : "Malformed BlockInfo";
for(int idx = getCapacity()-1; idx >= 0; idx--) {
if(getDatanode(idx) != null)
return idx+1;
}
return 0;
}
/**
* Add data-node this block belongs to.
*/
boolean addNode(DatanodeDescriptor node) {
if(findDatanode(node) >= 0) // the node is already there
return false;
// find the last null node
int lastNode = ensureCapacity(1);
setDatanode(lastNode, node);
setNext(lastNode, null);
setPrevious(lastNode, null);
return true;
}
/**
* Remove data-node from the block.
*/
boolean removeNode(DatanodeDescriptor node) {
int dnIndex = findDatanode(node);
if(dnIndex < 0) // the node is not found
return false;
assert getPrevious(dnIndex) == null && getNext(dnIndex) == null :
"Block is still in the list and must be removed first.";
// find the last not null node
int lastNode = numNodes()-1;
// replace current node triplet by the lastNode one
setDatanode(dnIndex, getDatanode(lastNode));
setNext(dnIndex, getNext(lastNode));
setPrevious(dnIndex, getPrevious(lastNode));
// set the last triplet to null
setDatanode(lastNode, null);
setNext(lastNode, null);
setPrevious(lastNode, null);
return true;
}
/**
* Find specified DatanodeDescriptor.
* @param dn
* @return index or -1 if not found.
*/
int findDatanode(DatanodeDescriptor dn) {
int len = getCapacity();
for(int idx = 0; idx < len; idx++) {
DatanodeDescriptor cur = getDatanode(idx);
if(cur == dn)
return idx;
if(cur == null)
break;
}
return -1;
}
/**
* Insert this block into the head of the list of blocks
* related to the specified DatanodeDescriptor.
* If the head is null then form a new list.
* @return current block as the new head of the list.
*/
BlockInfo listInsert(BlockInfo head, DatanodeDescriptor dn) {
int dnIndex = this.findDatanode(dn);
assert dnIndex >= 0 : "Data node is not found: current";
assert getPrevious(dnIndex) == null && getNext(dnIndex) == null :
"Block is already in the list and cannot be inserted.";
this.setPrevious(dnIndex, null);
this.setNext(dnIndex, head);
if(head != null)
head.setPrevious(head.findDatanode(dn), this);
return this;
}
/**
* Remove this block from the list of blocks
* related to the specified DatanodeDescriptor.
* If this block is the head of the list then return the next block as
* the new head.
* @return the new head of the list or null if the list becomes
* empy after deletion.
*/
BlockInfo listRemove(BlockInfo head, DatanodeDescriptor dn) {
if(head == null)
return null;
int dnIndex = this.findDatanode(dn);
if(dnIndex < 0) // this block is not on the data-node list
return head;
BlockInfo next = this.getNext(dnIndex);
BlockInfo prev = this.getPrevious(dnIndex);
this.setNext(dnIndex, null);
this.setPrevious(dnIndex, null);
if(prev != null)
prev.setNext(prev.findDatanode(dn), next);
if(next != null)
next.setPrevious(next.findDatanode(dn), prev);
if(this == head) // removing the head
head = next;
return head;
}
int listCount(DatanodeDescriptor dn) {
int count = 0;
for(BlockInfo cur = this; cur != null;
cur = cur.getNext(cur.findDatanode(dn)))
count++;
return count;
}
boolean listIsConsistent(DatanodeDescriptor dn) {
// going forward
int count = 0;
BlockInfo next, nextPrev;
BlockInfo cur = this;
while(cur != null) {
next = cur.getNext(cur.findDatanode(dn));
if(next != null) {
nextPrev = next.getPrevious(next.findDatanode(dn));
if(cur != nextPrev) {
System.out.println("Inconsistent list: cur->next->prev != cur");
return false;
}
}
cur = next;
count++;
}
return true;
}
@Override
public LightWeightGSet.LinkedElement getNext() {
return nextLinkedElement;
}
@Override
public void setNext(LightWeightGSet.LinkedElement next) {
this.nextLinkedElement = next;
}
}
private static class NodeIterator implements Iterator<DatanodeDescriptor> {
private BlockInfo blockInfo;
private int nextIdx = 0;
NodeIterator(BlockInfo blkInfo) {
this.blockInfo = blkInfo;
}
public boolean hasNext() {
return blockInfo != null && nextIdx < blockInfo.getCapacity()
&& blockInfo.getDatanode(nextIdx) != null;
}
public DatanodeDescriptor next() {
return blockInfo.getDatanode(nextIdx++);
}
public void remove() {
throw new UnsupportedOperationException("Sorry. can't remove.");
}
}
/** Constant {@link LightWeightGSet} capacity. */
private final int capacity;
private GSet<Block, BlockInfo> blocks;
BlocksMap(int initialCapacity, float loadFactor) {
// Use 2% of total memory to size the GSet capacity
this.capacity = LightWeightGSet.computeCapacity(2.0, "BlocksMap");
this.blocks = new LightWeightGSet<Block, BlockInfo>(capacity);
}
void close() {
blocks.clear();
}
/**
* Add BlockInfo if mapping does not exist.
*/
private BlockInfo checkBlockInfo(Block b, int replication) {
BlockInfo info = blocks.get(b);
if (info == null) {
info = new BlockInfo(b, replication);
blocks.put(info);
}
return info;
}
INodeFile getINode(Block b) {
BlockInfo info = blocks.get(b);
return (info != null) ? info.inode : null;
}
/**
* Add block b belonging to the specified file inode to the map.
*/
BlockInfo addINode(Block b, INodeFile iNode) {
BlockInfo info = checkBlockInfo(b, iNode.getReplication());
info.inode = iNode;
return info;
}
/**
* Remove INode reference from block b.
* If it does not belong to any file and data-nodes,
* then remove the block from the block map.
*/
void removeINode(Block b) {
BlockInfo info = blocks.get(b);
if (info != null) {
info.inode = null;
if (info.getDatanode(0) == null) { // no datanodes left
blocks.remove(b); // remove block from the map
}
}
}
/**
* Remove the block from the block map;
* remove it from all data-node lists it belongs to;
* and remove all data-node locations associated with the block.
*/
void removeBlock(BlockInfo blockInfo) {
if (blockInfo == null)
return;
blockInfo.inode = null;
for(int idx = blockInfo.numNodes()-1; idx >= 0; idx--) {
DatanodeDescriptor dn = blockInfo.getDatanode(idx);
dn.removeBlock(blockInfo); // remove from the list and wipe the location
}
blocks.remove(blockInfo); // remove block from the map
}
/** Returns the block object it it exists in the map. */
BlockInfo getStoredBlock(Block b) {
return blocks.get(b);
}
/** Return the block object without matching against generation stamp. */
BlockInfo getStoredBlockWithoutMatchingGS(Block b) {
return blocks.get(new Block(b.getBlockId()));
}
/** Returned Iterator does not support. */
Iterator<DatanodeDescriptor> nodeIterator(Block b) {
return new NodeIterator(blocks.get(b));
}
/** counts number of containing nodes. Better than using iterator. */
int numNodes(Block b) {
BlockInfo info = blocks.get(b);
return info == null ? 0 : info.numNodes();
}
/** returns true if the node does not already exists and is added.
* false if the node already exists.*/
boolean addNode(Block b, DatanodeDescriptor node, int replication) {
// insert into the map if not there yet
BlockInfo info = checkBlockInfo(b, replication);
// add block to the data-node list and the node to the block info
return node.addBlock(info);
}
/**
* Remove data-node reference from the block.
* Remove the block from the block map
* only if it does not belong to any file and data-nodes.
*/
boolean removeNode(Block b, DatanodeDescriptor node) {
BlockInfo info = blocks.get(b);
if (info == null)
return false;
// remove block from the data-node list and the node from the block info
boolean removed = node.removeBlock(info);
if (info.getDatanode(0) == null // no datanodes left
&& info.inode == null) { // does not belong to a file
blocks.remove(b); // remove block from the map
}
return removed;
}
int size() {
return blocks.size();
}
Iterable<BlockInfo> getBlocks() {
return blocks;
}
/**
* Check if the block exists in map
*/
boolean contains(Block block) {
return blocks.contains(block);
}
/**
* Check if the replica at the given datanode exists in map
*/
boolean contains(Block block, DatanodeDescriptor datanode) {
BlockInfo info = blocks.get(block);
if (info == null)
return false;
if (-1 == info.findDatanode(datanode))
return false;
return true;
}
/** Get the capacity of the HashMap that stores blocks */
public int getCapacity() {
return capacity;
}
}