/**
* 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 java.util.LinkedList;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.BlockUCState;
import org.apache.hadoop.util.LightWeightGSet;
/**
* BlockInfo class maintains for a given block
* the {@link INodeFile} it is part of and datanodes where the replicas of
* the block are stored.
* BlockInfo class maintains for a given block
* the {@link BlockCollection} it is part of and datanodes where the replicas of
* the block are stored.
*/
@InterfaceAudience.Private
public class BlockInfo extends Block implements LightWeightGSet.LinkedElement {
public static final BlockInfo[] EMPTY_ARRAY = {};
private BlockCollection bc;
/** For implementing {@link LightWeightGSet.LinkedElement} interface */
private LightWeightGSet.LinkedElement nextLinkedElement;
/**
* This array contains triplets of references. For each i-th datanode 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.
*
* Using previous and next in Object triplets is done instead of a
* {@link LinkedList} list to efficiently use memory. With LinkedList the cost
* per replica is 42 bytes (LinkedList#Entry object per replica) versus 16
* bytes using the triplets.
*/
private Object[] triplets;
/**
* Construct an entry for blocksmap
* @param replication the block's replication factor
*/
public BlockInfo(int replication) {
this.triplets = new Object[3*replication];
this.bc = null;
}
public BlockInfo(Block blk, int replication) {
super(blk);
this.triplets = new Object[3*replication];
this.bc = null;
}
/**
* Copy construction.
* This is used to convert BlockInfoUnderConstruction
* @param from BlockInfo to copy from.
*/
protected BlockInfo(BlockInfo from) {
this(from, from.bc.getBlockReplication());
this.bc = from.bc;
}
public BlockCollection getBlockCollection() {
return bc;
}
public void setBlockCollection(BlockCollection bc) {
this.bc = bc;
}
DatanodeDescriptor getDatanode(int index) {
assert this.triplets != null : "BlockInfo is not initialized";
assert index >= 0 && index*3 < triplets.length : "Index is out of bound";
return (DatanodeDescriptor)triplets[index*3];
}
private 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 ||
info.getClass().getName().startsWith(BlockInfo.class.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 ||
info.getClass().getName().startsWith(BlockInfo.class.getName()) :
"BlockInfo is expected at " + index*3;
return info;
}
private void setDatanode(int index, DatanodeDescriptor node, BlockInfo previous,
BlockInfo next) {
assert this.triplets != null : "BlockInfo is not initialized";
int i = index * 3;
assert index >= 0 && i+2 < triplets.length : "Index is out of bound";
triplets[i] = node;
triplets[i+1] = previous;
triplets[i+2] = next;
}
/**
* Return the previous block on the block list for the datanode at
* position index. Set the previous block on the list to "to".
*
* @param index - the datanode index
* @param to - block to be set to previous on the list of blocks
* @return current previous block on the list of blocks
*/
private BlockInfo 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";
BlockInfo info = (BlockInfo)triplets[index*3+1];
triplets[index*3+1] = to;
return info;
}
/**
* Return the next block on the block list for the datanode at
* position index. Set the next block on the list to "to".
*
* @param index - the datanode index
* @param to - block to be set to next on the list of blocks
* * @return current next block on the list of blocks
*/
private BlockInfo 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";
BlockInfo info = (BlockInfo)triplets[index*3+2];
triplets[index*3+2] = to;
return info;
}
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];
System.arraycopy(old, 0, triplets, 0, last*3);
return last;
}
/**
* Count the number of data-nodes the block belongs to.
*/
public 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.
*/
public 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, null, null);
return true;
}
/**
* Remove data-node from the block.
*/
public 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), getPrevious(lastNode),
getNext(lastNode));
// set the last triplet to null
setDatanode(lastNode, null, null, 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.
*/
public 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
* empty after deletion.
*/
public 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;
}
/**
* Remove this block from the list of blocks related to the specified
* DatanodeDescriptor. Insert it into the head of the list of blocks.
*
* @return the new head of the list.
*/
public BlockInfo moveBlockToHead(BlockInfo head, DatanodeDescriptor dn,
int curIndex, int headIndex) {
if (head == this) {
return this;
}
BlockInfo next = this.setNext(curIndex, head);
BlockInfo prev = this.setPrevious(curIndex, null);
head.setPrevious(headIndex, this);
prev.setNext(prev.findDatanode(dn), next);
if (next != null)
next.setPrevious(next.findDatanode(dn), prev);
return this;
}
/**
* BlockInfo represents a block that is not being constructed.
* In order to start modifying the block, the BlockInfo should be converted
* to {@link BlockInfoUnderConstruction}.
* @return {@link BlockUCState#COMPLETE}
*/
public BlockUCState getBlockUCState() {
return BlockUCState.COMPLETE;
}
/**
* Is this block complete?
*
* @return true if the state of the block is {@link BlockUCState#COMPLETE}
*/
public boolean isComplete() {
return getBlockUCState().equals(BlockUCState.COMPLETE);
}
/**
* Convert a complete block to an under construction block.
* @return BlockInfoUnderConstruction - an under construction block.
*/
public BlockInfoUnderConstruction convertToBlockUnderConstruction(
BlockUCState s, DatanodeDescriptor[] targets) {
if(isComplete()) {
return new BlockInfoUnderConstruction(
this, getBlockCollection().getBlockReplication(), s, targets);
}
// the block is already under construction
BlockInfoUnderConstruction ucBlock = (BlockInfoUnderConstruction)this;
ucBlock.setBlockUCState(s);
ucBlock.setExpectedLocations(targets);
return ucBlock;
}
@Override
public int hashCode() {
// Super implementation is sufficient
return super.hashCode();
}
@Override
public boolean equals(Object obj) {
// Sufficient to rely on super's implementation
return (this == obj) || super.equals(obj);
}
@Override
public LightWeightGSet.LinkedElement getNext() {
return nextLinkedElement;
}
@Override
public void setNext(LightWeightGSet.LinkedElement next) {
this.nextLinkedElement = next;
}
}