/**
* 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 static org.apache.hadoop.util.Time.monotonicNow;
import java.util.*;
import com.google.common.base.Preconditions;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.StorageType;
import org.apache.hadoop.hdfs.protocol.BlockStoragePolicy;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.net.NetworkTopology;
import org.apache.hadoop.net.Node;
import org.apache.hadoop.net.NodeBase;
import com.google.common.annotations.VisibleForTesting;
/**
* The class is responsible for choosing the desired number of targets
* for placing block replicas.
* The replica placement strategy is that if the writer is on a datanode,
* the 1st replica is placed on the local machine,
* otherwise a random datanode. The 2nd replica is placed on a datanode
* that is on a different rack. The 3rd replica is placed on a datanode
* which is on a different node of the rack as the second replica.
*/
@InterfaceAudience.Private
public class BlockPlacementPolicyDefault extends BlockPlacementPolicy {
private static final String enableDebugLogging =
"For more information, please enable DEBUG log level on "
+ BlockPlacementPolicy.class.getName() + " and "
+ NetworkTopology.class.getName();
private static final ThreadLocal<StringBuilder> debugLoggingBuilder
= new ThreadLocal<StringBuilder>() {
@Override
protected StringBuilder initialValue() {
return new StringBuilder();
}
};
protected boolean considerLoad;
private boolean preferLocalNode;
protected NetworkTopology clusterMap;
protected Host2NodesMap host2datanodeMap;
private FSClusterStats stats;
protected long heartbeatInterval; // interval for DataNode heartbeats
private long staleInterval; // interval used to identify stale DataNodes
/**
* A miss of that many heartbeats is tolerated for replica deletion policy.
*/
protected int tolerateHeartbeatMultiplier;
protected BlockPlacementPolicyDefault() {
}
@Override
public void initialize(Configuration conf, FSClusterStats stats,
NetworkTopology clusterMap,
Host2NodesMap host2datanodeMap) {
this.considerLoad = conf.getBoolean(
DFSConfigKeys.DFS_NAMENODE_REPLICATION_CONSIDERLOAD_KEY, true);
this.stats = stats;
this.clusterMap = clusterMap;
this.host2datanodeMap = host2datanodeMap;
this.heartbeatInterval = conf.getLong(
DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY,
DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_DEFAULT) * 1000;
this.tolerateHeartbeatMultiplier = conf.getInt(
DFSConfigKeys.DFS_NAMENODE_TOLERATE_HEARTBEAT_MULTIPLIER_KEY,
DFSConfigKeys.DFS_NAMENODE_TOLERATE_HEARTBEAT_MULTIPLIER_DEFAULT);
this.staleInterval = conf.getLong(
DFSConfigKeys.DFS_NAMENODE_STALE_DATANODE_INTERVAL_KEY,
DFSConfigKeys.DFS_NAMENODE_STALE_DATANODE_INTERVAL_DEFAULT);
this.preferLocalNode = conf.getBoolean(
DFSConfigKeys.
DFS_NAMENODE_BLOCKPLACEMENTPOLICY_DEFAULT_PREFER_LOCAL_NODE_KEY,
DFSConfigKeys.
DFS_NAMENODE_BLOCKPLACEMENTPOLICY_DEFAULT_PREFER_LOCAL_NODE_DEFAULT);
}
@Override
public DatanodeStorageInfo[] chooseTarget(String srcPath,
int numOfReplicas,
Node writer,
List<DatanodeStorageInfo> chosenNodes,
boolean returnChosenNodes,
Set<Node> excludedNodes,
long blocksize,
final BlockStoragePolicy storagePolicy) {
return chooseTarget(numOfReplicas, writer, chosenNodes, returnChosenNodes,
excludedNodes, blocksize, storagePolicy);
}
@Override
DatanodeStorageInfo[] chooseTarget(String src,
int numOfReplicas,
Node writer,
Set<Node> excludedNodes,
long blocksize,
List<DatanodeDescriptor> favoredNodes,
BlockStoragePolicy storagePolicy) {
try {
if (favoredNodes == null || favoredNodes.size() == 0) {
// Favored nodes not specified, fall back to regular block placement.
return chooseTarget(src, numOfReplicas, writer,
new ArrayList<DatanodeStorageInfo>(numOfReplicas), false,
excludedNodes, blocksize, storagePolicy);
}
Set<Node> favoriteAndExcludedNodes = excludedNodes == null ?
new HashSet<Node>() : new HashSet<Node>(excludedNodes);
final List<StorageType> requiredStorageTypes = storagePolicy
.chooseStorageTypes((short)numOfReplicas);
final EnumMap<StorageType, Integer> storageTypes =
getRequiredStorageTypes(requiredStorageTypes);
// Choose favored nodes
List<DatanodeStorageInfo> results = new ArrayList<DatanodeStorageInfo>();
boolean avoidStaleNodes = stats != null
&& stats.isAvoidingStaleDataNodesForWrite();
int maxNodesAndReplicas[] = getMaxNodesPerRack(0, numOfReplicas);
numOfReplicas = maxNodesAndReplicas[0];
int maxNodesPerRack = maxNodesAndReplicas[1];
for (int i = 0; i < favoredNodes.size() && results.size() < numOfReplicas; i++) {
DatanodeDescriptor favoredNode = favoredNodes.get(i);
// Choose a single node which is local to favoredNode.
// 'results' is updated within chooseLocalNode
final DatanodeStorageInfo target = chooseLocalStorage(favoredNode,
favoriteAndExcludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes, false);
if (target == null) {
LOG.warn("Could not find a target for file " + src
+ " with favored node " + favoredNode);
continue;
}
favoriteAndExcludedNodes.add(target.getDatanodeDescriptor());
}
if (results.size() < numOfReplicas) {
// Not enough favored nodes, choose other nodes.
numOfReplicas -= results.size();
DatanodeStorageInfo[] remainingTargets =
chooseTarget(src, numOfReplicas, writer, results,
false, favoriteAndExcludedNodes, blocksize, storagePolicy);
for (int i = 0; i < remainingTargets.length; i++) {
results.add(remainingTargets[i]);
}
}
return getPipeline(writer,
results.toArray(new DatanodeStorageInfo[results.size()]));
} catch (NotEnoughReplicasException nr) {
if (LOG.isDebugEnabled()) {
LOG.debug("Failed to choose with favored nodes (=" + favoredNodes
+ "), disregard favored nodes hint and retry.", nr);
}
// Fall back to regular block placement disregarding favored nodes hint
return chooseTarget(src, numOfReplicas, writer,
new ArrayList<DatanodeStorageInfo>(numOfReplicas), false,
excludedNodes, blocksize, storagePolicy);
}
}
/** This is the implementation. */
private DatanodeStorageInfo[] chooseTarget(int numOfReplicas,
Node writer,
List<DatanodeStorageInfo> chosenStorage,
boolean returnChosenNodes,
Set<Node> excludedNodes,
long blocksize,
final BlockStoragePolicy storagePolicy) {
if (numOfReplicas == 0 || clusterMap.getNumOfLeaves()==0) {
return DatanodeStorageInfo.EMPTY_ARRAY;
}
if (excludedNodes == null) {
excludedNodes = new HashSet<Node>();
}
int[] result = getMaxNodesPerRack(chosenStorage.size(), numOfReplicas);
numOfReplicas = result[0];
int maxNodesPerRack = result[1];
final List<DatanodeStorageInfo> results = new ArrayList<DatanodeStorageInfo>(chosenStorage);
for (DatanodeStorageInfo storage : chosenStorage) {
// add localMachine and related nodes to excludedNodes
addToExcludedNodes(storage.getDatanodeDescriptor(), excludedNodes);
}
boolean avoidStaleNodes = (stats != null
&& stats.isAvoidingStaleDataNodesForWrite());
final Node localNode = chooseTarget(numOfReplicas, writer, excludedNodes,
blocksize, maxNodesPerRack, results, avoidStaleNodes, storagePolicy,
EnumSet.noneOf(StorageType.class), results.isEmpty());
if (!returnChosenNodes) {
results.removeAll(chosenStorage);
}
// sorting nodes to form a pipeline
return getPipeline(
(writer != null && writer instanceof DatanodeDescriptor) ? writer
: localNode,
results.toArray(new DatanodeStorageInfo[results.size()]));
}
/**
* Calculate the maximum number of replicas to allocate per rack. It also
* limits the total number of replicas to the total number of nodes in the
* cluster. Caller should adjust the replica count to the return value.
*
* @param numOfChosen The number of already chosen nodes.
* @param numOfReplicas The number of additional nodes to allocate.
* @return integer array. Index 0: The number of nodes allowed to allocate
* in addition to already chosen nodes.
* Index 1: The maximum allowed number of nodes per rack. This
* is independent of the number of chosen nodes, as it is calculated
* using the target number of replicas.
*/
private int[] getMaxNodesPerRack(int numOfChosen, int numOfReplicas) {
int clusterSize = clusterMap.getNumOfLeaves();
int totalNumOfReplicas = numOfChosen + numOfReplicas;
if (totalNumOfReplicas > clusterSize) {
numOfReplicas -= (totalNumOfReplicas-clusterSize);
totalNumOfReplicas = clusterSize;
}
// No calculation needed when there is only one rack or picking one node.
int numOfRacks = clusterMap.getNumOfRacks();
if (numOfRacks == 1 || totalNumOfReplicas <= 1) {
return new int[] {numOfReplicas, totalNumOfReplicas};
}
int maxNodesPerRack = (totalNumOfReplicas-1)/numOfRacks + 2;
// At this point, there are more than one racks and more than one replicas
// to store. Avoid all replicas being in the same rack.
//
// maxNodesPerRack has the following properties at this stage.
// 1) maxNodesPerRack >= 2
// 2) (maxNodesPerRack-1) * numOfRacks > totalNumOfReplicas
// when numOfRacks > 1
//
// Thus, the following adjustment will still result in a value that forces
// multi-rack allocation and gives enough number of total nodes.
if (maxNodesPerRack == totalNumOfReplicas) {
maxNodesPerRack--;
}
return new int[] {numOfReplicas, maxNodesPerRack};
}
private EnumMap<StorageType, Integer> getRequiredStorageTypes(
List<StorageType> types) {
EnumMap<StorageType, Integer> map = new EnumMap<StorageType,
Integer>(StorageType.class);
for (StorageType type : types) {
if (!map.containsKey(type)) {
map.put(type, 1);
} else {
int num = map.get(type);
map.put(type, num + 1);
}
}
return map;
}
/**
* choose <i>numOfReplicas</i> from all data nodes
* @param numOfReplicas additional number of replicas wanted
* @param writer the writer's machine, could be a non-DatanodeDescriptor node
* @param excludedNodes datanodes that should not be considered as targets
* @param blocksize size of the data to be written
* @param maxNodesPerRack max nodes allowed per rack
* @param results the target nodes already chosen
* @param avoidStaleNodes avoid stale nodes in replica choosing
* @return local node of writer (not chosen node)
*/
private Node chooseTarget(int numOfReplicas,
Node writer,
final Set<Node> excludedNodes,
final long blocksize,
final int maxNodesPerRack,
final List<DatanodeStorageInfo> results,
final boolean avoidStaleNodes,
final BlockStoragePolicy storagePolicy,
final EnumSet<StorageType> unavailableStorages,
final boolean newBlock) {
if (numOfReplicas == 0 || clusterMap.getNumOfLeaves()==0) {
return (writer instanceof DatanodeDescriptor) ? writer : null;
}
final int numOfResults = results.size();
final int totalReplicasExpected = numOfReplicas + numOfResults;
if ((writer == null || !(writer instanceof DatanodeDescriptor)) && !newBlock) {
writer = results.get(0).getDatanodeDescriptor();
}
// Keep a copy of original excludedNodes
final Set<Node> oldExcludedNodes = new HashSet<Node>(excludedNodes);
// choose storage types; use fallbacks for unavailable storages
final List<StorageType> requiredStorageTypes = storagePolicy
.chooseStorageTypes((short) totalReplicasExpected,
DatanodeStorageInfo.toStorageTypes(results),
unavailableStorages, newBlock);
final EnumMap<StorageType, Integer> storageTypes =
getRequiredStorageTypes(requiredStorageTypes);
if (LOG.isTraceEnabled()) {
LOG.trace("storageTypes=" + storageTypes);
}
try {
if ((numOfReplicas = requiredStorageTypes.size()) == 0) {
throw new NotEnoughReplicasException(
"All required storage types are unavailable: "
+ " unavailableStorages=" + unavailableStorages
+ ", storagePolicy=" + storagePolicy);
}
if (numOfResults == 0) {
writer = chooseLocalStorage(writer, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes, true)
.getDatanodeDescriptor();
if (--numOfReplicas == 0) {
return writer;
}
}
final DatanodeDescriptor dn0 = results.get(0).getDatanodeDescriptor();
if (numOfResults <= 1) {
chooseRemoteRack(1, dn0, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
if (--numOfReplicas == 0) {
return writer;
}
}
if (numOfResults <= 2) {
final DatanodeDescriptor dn1 = results.get(1).getDatanodeDescriptor();
if (clusterMap.isOnSameRack(dn0, dn1)) {
chooseRemoteRack(1, dn0, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
} else if (newBlock){
chooseLocalRack(dn1, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
} else {
chooseLocalRack(writer, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
}
if (--numOfReplicas == 0) {
return writer;
}
}
chooseRandom(numOfReplicas, NodeBase.ROOT, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
} catch (NotEnoughReplicasException e) {
final String message = "Failed to place enough replicas, still in need of "
+ (totalReplicasExpected - results.size()) + " to reach "
+ totalReplicasExpected
+ " (unavailableStorages=" + unavailableStorages
+ ", storagePolicy=" + storagePolicy
+ ", newBlock=" + newBlock + ")";
if (LOG.isTraceEnabled()) {
LOG.trace(message, e);
} else {
LOG.warn(message + " " + e.getMessage());
}
if (avoidStaleNodes) {
// Retry chooseTarget again, this time not avoiding stale nodes.
// excludedNodes contains the initial excludedNodes and nodes that were
// not chosen because they were stale, decommissioned, etc.
// We need to additionally exclude the nodes that were added to the
// result list in the successful calls to choose*() above.
for (DatanodeStorageInfo resultStorage : results) {
addToExcludedNodes(resultStorage.getDatanodeDescriptor(), oldExcludedNodes);
}
// Set numOfReplicas, since it can get out of sync with the result list
// if the NotEnoughReplicasException was thrown in chooseRandom().
numOfReplicas = totalReplicasExpected - results.size();
return chooseTarget(numOfReplicas, writer, oldExcludedNodes, blocksize,
maxNodesPerRack, results, false, storagePolicy, unavailableStorages,
newBlock);
}
boolean retry = false;
// simply add all the remaining types into unavailableStorages and give
// another try. No best effort is guaranteed here.
for (StorageType type : storageTypes.keySet()) {
if (!unavailableStorages.contains(type)) {
unavailableStorages.add(type);
retry = true;
}
}
if (retry) {
for (DatanodeStorageInfo resultStorage : results) {
addToExcludedNodes(resultStorage.getDatanodeDescriptor(),
oldExcludedNodes);
}
numOfReplicas = totalReplicasExpected - results.size();
return chooseTarget(numOfReplicas, writer, oldExcludedNodes, blocksize,
maxNodesPerRack, results, false, storagePolicy, unavailableStorages,
newBlock);
}
}
return writer;
}
protected DatanodeStorageInfo chooseLocalStorage(Node localMachine,
Set<Node> excludedNodes, long blocksize, int maxNodesPerRack,
List<DatanodeStorageInfo> results, boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes)
throws NotEnoughReplicasException {
// if no local machine, randomly choose one node
if (localMachine == null) {
return chooseRandom(NodeBase.ROOT, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
if (preferLocalNode && localMachine instanceof DatanodeDescriptor) {
DatanodeDescriptor localDatanode = (DatanodeDescriptor) localMachine;
// otherwise try local machine first
if (excludedNodes.add(localMachine) // was not in the excluded list
&& isGoodDatanode(localDatanode, maxNodesPerRack, false,
results, avoidStaleNodes)) {
for (Iterator<Map.Entry<StorageType, Integer>> iter = storageTypes
.entrySet().iterator(); iter.hasNext(); ) {
Map.Entry<StorageType, Integer> entry = iter.next();
DatanodeStorageInfo localStorage = chooseStorage4Block(
localDatanode, blocksize, results, entry.getKey());
if (localStorage != null) {
// add node and related nodes to excludedNode
addToExcludedNodes(localDatanode, excludedNodes);
int num = entry.getValue();
if (num == 1) {
iter.remove();
} else {
entry.setValue(num - 1);
}
return localStorage;
}
}
}
}
return null;
}
/**
* Choose <i>localMachine</i> as the target.
* if <i>localMachine</i> is not available,
* choose a node on the same rack
* @return the chosen storage
*/
protected DatanodeStorageInfo chooseLocalStorage(Node localMachine,
Set<Node> excludedNodes, long blocksize, int maxNodesPerRack,
List<DatanodeStorageInfo> results, boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes, boolean fallbackToLocalRack)
throws NotEnoughReplicasException {
DatanodeStorageInfo localStorage = chooseLocalStorage(localMachine,
excludedNodes, blocksize, maxNodesPerRack, results,
avoidStaleNodes, storageTypes);
if (localStorage != null) {
return localStorage;
}
if (!fallbackToLocalRack) {
return null;
}
// try a node on local rack
return chooseLocalRack(localMachine, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
/**
* Add <i>localMachine</i> and related nodes to <i>excludedNodes</i>
* for next replica choosing. In sub class, we can add more nodes within
* the same failure domain of localMachine
* @return number of new excluded nodes
*/
protected int addToExcludedNodes(DatanodeDescriptor localMachine,
Set<Node> excludedNodes) {
return excludedNodes.add(localMachine) ? 1 : 0;
}
/**
* Choose one node from the rack that <i>localMachine</i> is on.
* if no such node is available, choose one node from the rack where
* a second replica is on.
* if still no such node is available, choose a random node
* in the cluster.
* @return the chosen node
*/
protected DatanodeStorageInfo chooseLocalRack(Node localMachine,
Set<Node> excludedNodes,
long blocksize,
int maxNodesPerRack,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes)
throws NotEnoughReplicasException {
// no local machine, so choose a random machine
if (localMachine == null) {
return chooseRandom(NodeBase.ROOT, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
final String localRack = localMachine.getNetworkLocation();
try {
// choose one from the local rack
return chooseRandom(localRack, excludedNodes,
blocksize, maxNodesPerRack, results, avoidStaleNodes, storageTypes);
} catch (NotEnoughReplicasException e) {
// find the next replica and retry with its rack
for(DatanodeStorageInfo resultStorage : results) {
DatanodeDescriptor nextNode = resultStorage.getDatanodeDescriptor();
if (nextNode != localMachine) {
if (LOG.isDebugEnabled()) {
LOG.debug("Failed to choose from local rack (location = " + localRack
+ "), retry with the rack of the next replica (location = "
+ nextNode.getNetworkLocation() + ")", e);
}
return chooseFromNextRack(nextNode, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
}
if (LOG.isDebugEnabled()) {
LOG.debug("Failed to choose from local rack (location = " + localRack
+ "); the second replica is not found, retry choosing ramdomly", e);
}
//the second replica is not found, randomly choose one from the network
return chooseRandom(NodeBase.ROOT, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
}
private DatanodeStorageInfo chooseFromNextRack(Node next,
Set<Node> excludedNodes,
long blocksize,
int maxNodesPerRack,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes) throws NotEnoughReplicasException {
final String nextRack = next.getNetworkLocation();
try {
return chooseRandom(nextRack, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
} catch(NotEnoughReplicasException e) {
if (LOG.isDebugEnabled()) {
LOG.debug("Failed to choose from the next rack (location = " + nextRack
+ "), retry choosing ramdomly", e);
}
//otherwise randomly choose one from the network
return chooseRandom(NodeBase.ROOT, excludedNodes, blocksize,
maxNodesPerRack, results, avoidStaleNodes, storageTypes);
}
}
/**
* Choose <i>numOfReplicas</i> nodes from the racks
* that <i>localMachine</i> is NOT on.
* If not enough nodes are available, choose the remaining ones
* from the local rack
*/
protected void chooseRemoteRack(int numOfReplicas,
DatanodeDescriptor localMachine,
Set<Node> excludedNodes,
long blocksize,
int maxReplicasPerRack,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes)
throws NotEnoughReplicasException {
int oldNumOfReplicas = results.size();
// randomly choose one node from remote racks
try {
chooseRandom(numOfReplicas, "~" + localMachine.getNetworkLocation(),
excludedNodes, blocksize, maxReplicasPerRack, results,
avoidStaleNodes, storageTypes);
} catch (NotEnoughReplicasException e) {
if (LOG.isDebugEnabled()) {
LOG.debug("Failed to choose remote rack (location = ~"
+ localMachine.getNetworkLocation() + "), fallback to local rack", e);
}
chooseRandom(numOfReplicas-(results.size()-oldNumOfReplicas),
localMachine.getNetworkLocation(), excludedNodes, blocksize,
maxReplicasPerRack, results, avoidStaleNodes, storageTypes);
}
}
/**
* Randomly choose one target from the given <i>scope</i>.
* @return the chosen storage, if there is any.
*/
protected DatanodeStorageInfo chooseRandom(String scope,
Set<Node> excludedNodes,
long blocksize,
int maxNodesPerRack,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes)
throws NotEnoughReplicasException {
return chooseRandom(1, scope, excludedNodes, blocksize, maxNodesPerRack,
results, avoidStaleNodes, storageTypes);
}
/**
* Randomly choose <i>numOfReplicas</i> targets from the given <i>scope</i>.
* @return the first chosen node, if there is any.
*/
protected DatanodeStorageInfo chooseRandom(int numOfReplicas,
String scope,
Set<Node> excludedNodes,
long blocksize,
int maxNodesPerRack,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes,
EnumMap<StorageType, Integer> storageTypes)
throws NotEnoughReplicasException {
StringBuilder builder = null;
if (LOG.isDebugEnabled()) {
builder = debugLoggingBuilder.get();
builder.setLength(0);
builder.append("[");
}
boolean badTarget = false;
DatanodeStorageInfo firstChosen = null;
while (numOfReplicas > 0) {
DatanodeDescriptor chosenNode = chooseDataNode(scope, excludedNodes);
if (chosenNode == null) {
break;
}
Preconditions.checkState(excludedNodes.add(chosenNode), "chosenNode "
+ chosenNode + " is already in excludedNodes " + excludedNodes);
if (LOG.isDebugEnabled()) {
builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
.append(" [");
}
DatanodeStorageInfo storage = null;
if (isGoodDatanode(chosenNode, maxNodesPerRack, considerLoad,
results, avoidStaleNodes)) {
for (Iterator<Map.Entry<StorageType, Integer>> iter = storageTypes
.entrySet().iterator(); iter.hasNext();) {
Map.Entry<StorageType, Integer> entry = iter.next();
storage = chooseStorage4Block(
chosenNode, blocksize, results, entry.getKey());
if (storage != null) {
numOfReplicas--;
if (firstChosen == null) {
firstChosen = storage;
}
// add node (subclasses may also add related nodes) to excludedNode
addToExcludedNodes(chosenNode, excludedNodes);
int num = entry.getValue();
if (num == 1) {
iter.remove();
} else {
entry.setValue(num - 1);
}
break;
}
}
if (LOG.isDebugEnabled()) {
builder.append("\n]");
}
// If no candidate storage was found on this DN then set badTarget.
badTarget = (storage == null);
}
}
if (numOfReplicas>0) {
String detail = enableDebugLogging;
if (LOG.isDebugEnabled()) {
if (badTarget && builder != null) {
detail = builder.toString();
builder.setLength(0);
} else {
detail = "";
}
}
throw new NotEnoughReplicasException(detail);
}
return firstChosen;
}
/**
* Choose a datanode from the given <i>scope</i>.
* @return the chosen node, if there is any.
*/
protected DatanodeDescriptor chooseDataNode(final String scope,
final Collection<Node> excludedNodes) {
return (DatanodeDescriptor) clusterMap.chooseRandom(scope, excludedNodes);
}
/**
* Choose a good storage of given storage type from datanode, and add it to
* the result list.
*
* @param dnd datanode descriptor
* @param blockSize requested block size
* @param results the result storages
* @param storageType requested storage type
* @return the chosen datanode storage
*/
DatanodeStorageInfo chooseStorage4Block(DatanodeDescriptor dnd,
long blockSize,
List<DatanodeStorageInfo> results,
StorageType storageType) {
DatanodeStorageInfo storage =
dnd.chooseStorage4Block(storageType, blockSize);
if (storage != null) {
results.add(storage);
} else {
logNodeIsNotChosen(dnd, "no good storage to place the block ");
}
return storage;
}
private static void logNodeIsNotChosen(DatanodeDescriptor node,
String reason) {
if (LOG.isDebugEnabled()) {
// build the error message for later use.
debugLoggingBuilder.get()
.append("\n Datanode ").append(node)
.append(" is not chosen since ").append(reason).append(".");
}
}
/**
* Determine if a datanode is good for placing block.
*
* @param node The target datanode
* @param maxTargetPerRack Maximum number of targets per rack. The value of
* this parameter depends on the number of racks in
* the cluster and total number of replicas for a block
* @param considerLoad whether or not to consider load of the target node
* @param results A list containing currently chosen nodes. Used to check if
* too many nodes has been chosen in the target rack.
* @param avoidStaleNodes Whether or not to avoid choosing stale nodes
* @return Reture true if the datanode is good candidate, otherwise false
*/
boolean isGoodDatanode(DatanodeDescriptor node,
int maxTargetPerRack, boolean considerLoad,
List<DatanodeStorageInfo> results,
boolean avoidStaleNodes) {
// check if the node is (being) decommissioned
if (node.isDecommissionInProgress() || node.isDecommissioned()) {
logNodeIsNotChosen(node, "the node is (being) decommissioned ");
return false;
}
if (avoidStaleNodes) {
if (node.isStale(this.staleInterval)) {
logNodeIsNotChosen(node, "the node is stale ");
return false;
}
}
// check the communication traffic of the target machine
if (considerLoad) {
final double maxLoad = 2.0 * stats.getInServiceXceiverAverage();
final int nodeLoad = node.getXceiverCount();
if (nodeLoad > maxLoad) {
logNodeIsNotChosen(node, "the node is too busy (load: " + nodeLoad
+ " > " + maxLoad + ") ");
return false;
}
}
// check if the target rack has chosen too many nodes
String rackname = node.getNetworkLocation();
int counter=1;
for(DatanodeStorageInfo resultStorage : results) {
if (rackname.equals(
resultStorage.getDatanodeDescriptor().getNetworkLocation())) {
counter++;
}
}
if (counter > maxTargetPerRack) {
logNodeIsNotChosen(node, "the rack has too many chosen nodes ");
return false;
}
return true;
}
/**
* Return a pipeline of nodes.
* The pipeline is formed finding a shortest path that
* starts from the writer and traverses all <i>nodes</i>
* This is basically a traveling salesman problem.
*/
private DatanodeStorageInfo[] getPipeline(Node writer,
DatanodeStorageInfo[] storages) {
if (storages.length == 0) {
return storages;
}
synchronized(clusterMap) {
int index=0;
if (writer == null || !clusterMap.contains(writer)) {
writer = storages[0].getDatanodeDescriptor();
}
for(; index < storages.length; index++) {
DatanodeStorageInfo shortestStorage = storages[index];
int shortestDistance = clusterMap.getDistance(writer,
shortestStorage.getDatanodeDescriptor());
int shortestIndex = index;
for(int i = index + 1; i < storages.length; i++) {
int currentDistance = clusterMap.getDistance(writer,
storages[i].getDatanodeDescriptor());
if (shortestDistance>currentDistance) {
shortestDistance = currentDistance;
shortestStorage = storages[i];
shortestIndex = i;
}
}
//switch position index & shortestIndex
if (index != shortestIndex) {
storages[shortestIndex] = storages[index];
storages[index] = shortestStorage;
}
writer = shortestStorage.getDatanodeDescriptor();
}
}
return storages;
}
@Override
public BlockPlacementStatus verifyBlockPlacement(DatanodeInfo[] locs,
int numberOfReplicas) {
if (locs == null)
locs = DatanodeDescriptor.EMPTY_ARRAY;
if (!clusterMap.hasClusterEverBeenMultiRack()) {
// only one rack
return new BlockPlacementStatusDefault(1, 1);
}
int minRacks = 2;
minRacks = Math.min(minRacks, numberOfReplicas);
// 1. Check that all locations are different.
// 2. Count locations on different racks.
Set<String> racks = new TreeSet<String>();
for (DatanodeInfo dn : locs)
racks.add(dn.getNetworkLocation());
return new BlockPlacementStatusDefault(racks.size(), minRacks);
}
/**
* Decide whether deleting the specified replica of the block still makes
* the block conform to the configured block placement policy.
* @param moreThanOne The replica locations of this block that are present
* on more than one unique racks.
* @param exactlyOne Replica locations of this block that are present
* on exactly one unique racks.
* @param excessTypes The excess {@link StorageType}s according to the
* {@link BlockStoragePolicy}.
*
* @return the replica that is the best candidate for deletion
*/
@VisibleForTesting
public DatanodeStorageInfo chooseReplicaToDelete(
Collection<DatanodeStorageInfo> moreThanOne,
Collection<DatanodeStorageInfo> exactlyOne,
final List<StorageType> excessTypes,
Map<String, List<DatanodeStorageInfo>> rackMap) {
long oldestHeartbeat =
monotonicNow() - heartbeatInterval * tolerateHeartbeatMultiplier;
DatanodeStorageInfo oldestHeartbeatStorage = null;
long minSpace = Long.MAX_VALUE;
DatanodeStorageInfo minSpaceStorage = null;
// Pick the node with the oldest heartbeat or with the least free space,
// if all hearbeats are within the tolerable heartbeat interval
for(DatanodeStorageInfo storage : pickupReplicaSet(moreThanOne,
exactlyOne, rackMap)) {
if (!excessTypes.contains(storage.getStorageType())) {
continue;
}
final DatanodeDescriptor node = storage.getDatanodeDescriptor();
long free = node.getRemaining();
long lastHeartbeat = node.getLastUpdateMonotonic();
if (lastHeartbeat < oldestHeartbeat) {
oldestHeartbeat = lastHeartbeat;
oldestHeartbeatStorage = storage;
}
if (minSpace > free) {
minSpace = free;
minSpaceStorage = storage;
}
}
final DatanodeStorageInfo storage;
if (oldestHeartbeatStorage != null) {
storage = oldestHeartbeatStorage;
} else if (minSpaceStorage != null) {
storage = minSpaceStorage;
} else {
return null;
}
excessTypes.remove(storage.getStorageType());
return storage;
}
@Override
public List<DatanodeStorageInfo> chooseReplicasToDelete(
Collection<DatanodeStorageInfo> candidates,
int expectedNumOfReplicas,
List<StorageType> excessTypes,
DatanodeDescriptor addedNode,
DatanodeDescriptor delNodeHint) {
List<DatanodeStorageInfo> excessReplicas = new ArrayList<>();
final Map<String, List<DatanodeStorageInfo>> rackMap = new HashMap<>();
final List<DatanodeStorageInfo> moreThanOne = new ArrayList<>();
final List<DatanodeStorageInfo> exactlyOne = new ArrayList<>();
// split nodes into two sets
// moreThanOne contains nodes on rack with more than one replica
// exactlyOne contains the remaining nodes
splitNodesWithRack(candidates, rackMap, moreThanOne, exactlyOne);
// pick one node to delete that favors the delete hint
// otherwise pick one with least space from priSet if it is not empty
// otherwise one node with least space from remains
boolean firstOne = true;
final DatanodeStorageInfo delNodeHintStorage =
DatanodeStorageInfo.getDatanodeStorageInfo(candidates, delNodeHint);
final DatanodeStorageInfo addedNodeStorage =
DatanodeStorageInfo.getDatanodeStorageInfo(candidates, addedNode);
while (candidates.size() - expectedNumOfReplicas > excessReplicas.size()) {
final DatanodeStorageInfo cur;
if (useDelHint(firstOne, delNodeHintStorage, addedNodeStorage,
moreThanOne, excessTypes)) {
cur = delNodeHintStorage;
} else { // regular excessive replica removal
cur = chooseReplicaToDelete(moreThanOne, exactlyOne, excessTypes,
rackMap);
}
firstOne = false;
if (cur == null) {
if (LOG.isDebugEnabled()) {
LOG.debug("No excess replica can be found. excessTypes: {}." +
" moreThanOne: {}. exactlyOne: {}.", excessTypes,
moreThanOne, exactlyOne);
}
break;
}
// adjust rackmap, moreThanOne, and exactlyOne
adjustSetsWithChosenReplica(rackMap, moreThanOne, exactlyOne, cur);
excessReplicas.add(cur);
}
return excessReplicas;
}
/** Check if we can use delHint. */
@VisibleForTesting
static boolean useDelHint(boolean isFirst, DatanodeStorageInfo delHint,
DatanodeStorageInfo added, List<DatanodeStorageInfo> moreThan1Racks,
List<StorageType> excessTypes) {
if (!isFirst) {
return false; // only consider delHint for the first case
} else if (delHint == null) {
return false; // no delHint
} else if (!excessTypes.contains(delHint.getStorageType())) {
return false; // delHint storage type is not an excess type
} else {
// check if removing delHint reduces the number of racks
if (moreThan1Racks.contains(delHint)) {
return true; // delHint and some other nodes are under the same rack
} else if (added != null && !moreThan1Racks.contains(added)) {
return true; // the added node adds a new rack
}
return false; // removing delHint reduces the number of racks;
}
}
/**
* Pick up replica node set for deleting replica as over-replicated.
* First set contains replica nodes on rack with more than one
* replica while second set contains remaining replica nodes.
* If only 1 rack, pick all. If 2 racks, pick all that have more than
* 1 replicas on the same rack; if no such replicas, pick all.
* If 3 or more racks, pick all.
*/
protected Collection<DatanodeStorageInfo> pickupReplicaSet(
Collection<DatanodeStorageInfo> moreThanOne,
Collection<DatanodeStorageInfo> exactlyOne,
Map<String, List<DatanodeStorageInfo>> rackMap) {
Collection<DatanodeStorageInfo> ret = new ArrayList<>();
if (rackMap.size() == 2) {
for (List<DatanodeStorageInfo> dsi : rackMap.values()) {
if (dsi.size() >= 2) {
ret.addAll(dsi);
}
}
}
if (ret.isEmpty()) {
// Return all replicas if rackMap.size() != 2
// or rackMap.size() == 2 but no shared replicas on any rack
ret.addAll(moreThanOne);
ret.addAll(exactlyOne);
}
return ret;
}
@VisibleForTesting
void setPreferLocalNode(boolean prefer) {
this.preferLocalNode = prefer;
}
}