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/**
*
* 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.hbase.favored;
import static org.apache.hadoop.hbase.ServerName.NON_STARTCODE;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.Set;
import org.apache.commons.lang3.StringUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell.Type;
import org.apache.hadoop.hbase.CellBuilderFactory;
import org.apache.hadoop.hbase.CellBuilderType;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.MetaTableAccessor;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.client.Table;
import org.apache.hadoop.hbase.master.RackManager;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
import org.apache.hbase.thirdparty.com.google.common.collect.Sets;
import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.HBaseProtos;
import org.apache.hadoop.hbase.shaded.protobuf.generated.HBaseProtos.FavoredNodes;
/**
* Helper class for {@link FavoredNodeLoadBalancer} that has all the intelligence for racks,
* meta scans, etc. Instantiated by the {@link FavoredNodeLoadBalancer} when needed (from
* within calls like {@link FavoredNodeLoadBalancer#randomAssignment(RegionInfo, List)}).
* All updates to favored nodes should only be done from {@link FavoredNodesManager} and not
* through this helper class (except for tests).
*/
@InterfaceAudience.Private
public class FavoredNodeAssignmentHelper {
private static final Logger LOG = LoggerFactory.getLogger(FavoredNodeAssignmentHelper.class);
private RackManager rackManager;
private Map> rackToRegionServerMap;
private List uniqueRackList;
// This map serves as a cache for rack to sn lookups. The num of
// region server entries might not match with that is in servers.
private Map regionServerToRackMap;
private Random random;
private List servers;
public static final byte [] FAVOREDNODES_QUALIFIER = Bytes.toBytes("fn");
public final static short FAVORED_NODES_NUM = 3;
public final static short MAX_ATTEMPTS_FN_GENERATION = 10;
public FavoredNodeAssignmentHelper(final List servers, Configuration conf) {
this(servers, new RackManager(conf));
}
public FavoredNodeAssignmentHelper(final List servers,
final RackManager rackManager) {
this.servers = servers;
this.rackManager = rackManager;
this.rackToRegionServerMap = new HashMap<>();
this.regionServerToRackMap = new HashMap<>();
this.uniqueRackList = new ArrayList<>();
this.random = new Random();
}
// Always initialize() when FavoredNodeAssignmentHelper is constructed.
public void initialize() {
for (ServerName sn : this.servers) {
String rackName = getRackOfServer(sn);
List serverList = this.rackToRegionServerMap.get(rackName);
if (serverList == null) {
serverList = Lists.newArrayList();
// Add the current rack to the unique rack list
this.uniqueRackList.add(rackName);
this.rackToRegionServerMap.put(rackName, serverList);
}
for (ServerName serverName : serverList) {
if (ServerName.isSameAddress(sn, serverName)) {
// The server is already present, ignore.
break;
}
}
serverList.add((sn));
this.regionServerToRackMap.put(sn.getHostname(), rackName);
}
}
/**
* Update meta table with favored nodes info
* @param regionToFavoredNodes map of RegionInfo's to their favored nodes
* @param connection connection to be used
* @throws IOException
*/
public static void updateMetaWithFavoredNodesInfo(
Map> regionToFavoredNodes,
Connection connection) throws IOException {
List puts = new ArrayList<>();
for (Map.Entry> entry : regionToFavoredNodes.entrySet()) {
Put put = makePutFromRegionInfo(entry.getKey(), entry.getValue());
if (put != null) {
puts.add(put);
}
}
MetaTableAccessor.putsToMetaTable(connection, puts);
LOG.info("Added " + puts.size() + " regions in META");
}
/**
* Update meta table with favored nodes info
* @param regionToFavoredNodes
* @param conf
* @throws IOException
*/
public static void updateMetaWithFavoredNodesInfo(
Map> regionToFavoredNodes,
Configuration conf) throws IOException {
List puts = new ArrayList<>();
for (Map.Entry> entry : regionToFavoredNodes.entrySet()) {
Put put = makePutFromRegionInfo(entry.getKey(), entry.getValue());
if (put != null) {
puts.add(put);
}
}
// Write the region assignments to the meta table.
// TODO: See above overrides take a Connection rather than a Configuration only the
// Connection is a short circuit connection. That is not going to good in all cases, when
// master and meta are not colocated. Fix when this favored nodes feature is actually used
// someday.
try (Connection connection = ConnectionFactory.createConnection(conf)) {
try (Table metaTable = connection.getTable(TableName.META_TABLE_NAME)) {
metaTable.put(puts);
}
}
LOG.info("Added " + puts.size() + " regions in META");
}
/**
* Generates and returns a Put containing the region info for the catalog table and the servers
* @return Put object
*/
private static Put makePutFromRegionInfo(RegionInfo regionInfo, List favoredNodeList)
throws IOException {
Put put = null;
if (favoredNodeList != null) {
long time = EnvironmentEdgeManager.currentTime();
put = MetaTableAccessor.makePutFromRegionInfo(regionInfo, time);
byte[] favoredNodes = getFavoredNodes(favoredNodeList);
put.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY)
.setRow(put.getRow())
.setFamily(HConstants.CATALOG_FAMILY)
.setQualifier(FAVOREDNODES_QUALIFIER)
.setTimestamp(time)
.setType(Type.Put)
.setValue(favoredNodes)
.build());
LOG.debug("Create the region {} with favored nodes {}", regionInfo.getRegionNameAsString(),
favoredNodeList);
}
return put;
}
/**
* @param favoredNodes The PB'ed bytes of favored nodes
* @return the array of {@link ServerName} for the byte array of favored nodes.
* @throws IOException
*/
public static ServerName[] getFavoredNodesList(byte[] favoredNodes) throws IOException {
FavoredNodes f = FavoredNodes.parseFrom(favoredNodes);
List protoNodes = f.getFavoredNodeList();
ServerName[] servers = new ServerName[protoNodes.size()];
int i = 0;
for (HBaseProtos.ServerName node : protoNodes) {
servers[i++] = ProtobufUtil.toServerName(node);
}
return servers;
}
/**
* @param serverAddrList
* @return PB'ed bytes of {@link FavoredNodes} generated by the server list.
*/
public static byte[] getFavoredNodes(List serverAddrList) {
FavoredNodes.Builder f = FavoredNodes.newBuilder();
for (ServerName s : serverAddrList) {
HBaseProtos.ServerName.Builder b = HBaseProtos.ServerName.newBuilder();
b.setHostName(s.getHostname());
b.setPort(s.getPort());
b.setStartCode(ServerName.NON_STARTCODE);
f.addFavoredNode(b.build());
}
return f.build().toByteArray();
}
// Place the regions round-robin across the racks picking one server from each
// rack at a time. Start with a random rack, and a random server from every rack.
// If a rack doesn't have enough servers it will go to the next rack and so on.
// for choosing a primary.
// For example, if 4 racks (r1 .. r4) with 8 servers (s1..s8) each, one possible
// placement could be r2:s5, r3:s5, r4:s5, r1:s5, r2:s6, r3:s6..
// If there were fewer servers in one rack, say r3, which had 3 servers, one possible
// placement could be r2:s5, , r4:s5, r1:s5, r2:s6, ...
// The regions should be distributed proportionately to the racksizes
public void placePrimaryRSAsRoundRobin(Map> assignmentMap,
Map primaryRSMap, List regions) {
List rackList = new ArrayList<>(rackToRegionServerMap.size());
rackList.addAll(rackToRegionServerMap.keySet());
int rackIndex = random.nextInt(rackList.size());
int maxRackSize = 0;
for (Map.Entry> r : rackToRegionServerMap.entrySet()) {
if (r.getValue().size() > maxRackSize) {
maxRackSize = r.getValue().size();
}
}
int numIterations = 0;
// Initialize the current processing host index.
int serverIndex = random.nextInt(maxRackSize);
for (RegionInfo regionInfo : regions) {
List currentServerList;
String rackName;
while (true) {
rackName = rackList.get(rackIndex);
numIterations++;
// Get the server list for the current rack
currentServerList = rackToRegionServerMap.get(rackName);
if (serverIndex >= currentServerList.size()) { //not enough machines in this rack
if (numIterations % rackList.size() == 0) {
if (++serverIndex >= maxRackSize) serverIndex = 0;
}
if ((++rackIndex) >= rackList.size()) {
rackIndex = 0; // reset the rack index to 0
}
} else break;
}
// Get the current process region server
ServerName currentServer = currentServerList.get(serverIndex);
// Place the current region with the current primary region server
primaryRSMap.put(regionInfo, currentServer);
if (assignmentMap != null) {
List regionsForServer = assignmentMap.get(currentServer);
if (regionsForServer == null) {
regionsForServer = new ArrayList<>();
assignmentMap.put(currentServer, regionsForServer);
}
regionsForServer.add(regionInfo);
}
// Set the next processing index
if (numIterations % rackList.size() == 0) {
++serverIndex;
}
if ((++rackIndex) >= rackList.size()) {
rackIndex = 0; // reset the rack index to 0
}
}
}
public Map placeSecondaryAndTertiaryRS(
Map primaryRSMap) {
Map secondaryAndTertiaryMap = new HashMap<>();
for (Map.Entry entry : primaryRSMap.entrySet()) {
// Get the target region and its primary region server rack
RegionInfo regionInfo = entry.getKey();
ServerName primaryRS = entry.getValue();
try {
// Create the secondary and tertiary region server pair object.
ServerName[] favoredNodes = getSecondaryAndTertiary(regionInfo, primaryRS);
if (favoredNodes != null) {
secondaryAndTertiaryMap.put(regionInfo, favoredNodes);
LOG.debug("Place the secondary and tertiary region server for region "
+ regionInfo.getRegionNameAsString());
}
} catch (Exception e) {
LOG.warn("Cannot place the favored nodes for region " +
regionInfo.getRegionNameAsString() + " because " + e, e);
continue;
}
}
return secondaryAndTertiaryMap;
}
public ServerName[] getSecondaryAndTertiary(RegionInfo regionInfo, ServerName primaryRS)
throws IOException {
ServerName[] favoredNodes;// Get the rack for the primary region server
String primaryRack = getRackOfServer(primaryRS);
if (getTotalNumberOfRacks() == 1) {
favoredNodes = singleRackCase(regionInfo, primaryRS, primaryRack);
} else {
favoredNodes = multiRackCase(regionInfo, primaryRS, primaryRack);
}
return favoredNodes;
}
private Map> mapRSToPrimaries(
Map primaryRSMap) {
Map> primaryServerMap = new HashMap<>();
for (Entry e : primaryRSMap.entrySet()) {
Set currentSet = primaryServerMap.get(e.getValue());
if (currentSet == null) {
currentSet = new HashSet<>();
}
currentSet.add(e.getKey());
primaryServerMap.put(e.getValue(), currentSet);
}
return primaryServerMap;
}
/**
* For regions that share the primary, avoid placing the secondary and tertiary
* on a same RS. Used for generating new assignments for the
* primary/secondary/tertiary RegionServers
* @param primaryRSMap
* @return the map of regions to the servers the region-files should be hosted on
*/
public Map placeSecondaryAndTertiaryWithRestrictions(
Map primaryRSMap) {
Map> serverToPrimaries =
mapRSToPrimaries(primaryRSMap);
Map secondaryAndTertiaryMap = new HashMap<>();
for (Entry entry : primaryRSMap.entrySet()) {
// Get the target region and its primary region server rack
RegionInfo regionInfo = entry.getKey();
ServerName primaryRS = entry.getValue();
try {
// Get the rack for the primary region server
String primaryRack = getRackOfServer(primaryRS);
ServerName[] favoredNodes = null;
if (getTotalNumberOfRacks() == 1) {
// Single rack case: have to pick the secondary and tertiary
// from the same rack
favoredNodes = singleRackCase(regionInfo, primaryRS, primaryRack);
} else {
favoredNodes = multiRackCaseWithRestrictions(serverToPrimaries,
secondaryAndTertiaryMap, primaryRack, primaryRS, regionInfo);
}
if (favoredNodes != null) {
secondaryAndTertiaryMap.put(regionInfo, favoredNodes);
LOG.debug("Place the secondary and tertiary region server for region "
+ regionInfo.getRegionNameAsString());
}
} catch (Exception e) {
LOG.warn("Cannot place the favored nodes for region "
+ regionInfo.getRegionNameAsString() + " because " + e, e);
continue;
}
}
return secondaryAndTertiaryMap;
}
private ServerName[] multiRackCaseWithRestrictions(
Map> serverToPrimaries,
Map secondaryAndTertiaryMap,
String primaryRack, ServerName primaryRS, RegionInfo regionInfo) throws IOException {
// Random to choose the secondary and tertiary region server
// from another rack to place the secondary and tertiary
// Random to choose one rack except for the current rack
Set rackSkipSet = new HashSet<>();
rackSkipSet.add(primaryRack);
String secondaryRack = getOneRandomRack(rackSkipSet);
List serverList = getServersFromRack(secondaryRack);
Set serverSet = new HashSet<>(serverList);
ServerName[] favoredNodes;
if (serverList.size() >= 2) {
// Randomly pick up two servers from this secondary rack
// Skip the secondary for the tertiary placement
// skip the servers which share the primary already
Set primaries = serverToPrimaries.get(primaryRS);
Set skipServerSet = new HashSet<>();
while (true) {
ServerName[] secondaryAndTertiary = null;
if (primaries.size() > 1) {
// check where his tertiary and secondary are
for (RegionInfo primary : primaries) {
secondaryAndTertiary = secondaryAndTertiaryMap.get(primary);
if (secondaryAndTertiary != null) {
if (getRackOfServer(secondaryAndTertiary[0]).equals(secondaryRack)) {
skipServerSet.add(secondaryAndTertiary[0]);
}
if (getRackOfServer(secondaryAndTertiary[1]).equals(secondaryRack)) {
skipServerSet.add(secondaryAndTertiary[1]);
}
}
}
}
if (skipServerSet.size() + 2 <= serverSet.size())
break;
skipServerSet.clear();
rackSkipSet.add(secondaryRack);
// we used all racks
if (rackSkipSet.size() == getTotalNumberOfRacks()) {
// remove the last two added and break
skipServerSet.remove(secondaryAndTertiary[0]);
skipServerSet.remove(secondaryAndTertiary[1]);
break;
}
secondaryRack = getOneRandomRack(rackSkipSet);
serverList = getServersFromRack(secondaryRack);
serverSet = new HashSet<>(serverList);
}
// Place the secondary RS
ServerName secondaryRS = getOneRandomServer(secondaryRack, skipServerSet);
skipServerSet.add(secondaryRS);
// Place the tertiary RS
ServerName tertiaryRS = getOneRandomServer(secondaryRack, skipServerSet);
if (secondaryRS == null || tertiaryRS == null) {
LOG.error("Cannot place the secondary and tertiary"
+ " region server for region "
+ regionInfo.getRegionNameAsString());
}
// Create the secondary and tertiary pair
favoredNodes = new ServerName[2];
favoredNodes[0] = secondaryRS;
favoredNodes[1] = tertiaryRS;
} else {
// Pick the secondary rs from this secondary rack
// and pick the tertiary from another random rack
favoredNodes = new ServerName[2];
ServerName secondary = getOneRandomServer(secondaryRack);
favoredNodes[0] = secondary;
// Pick the tertiary
if (getTotalNumberOfRacks() == 2) {
// Pick the tertiary from the same rack of the primary RS
Set serverSkipSet = new HashSet<>();
serverSkipSet.add(primaryRS);
favoredNodes[1] = getOneRandomServer(primaryRack, serverSkipSet);
} else {
// Pick the tertiary from another rack
rackSkipSet.add(secondaryRack);
String tertiaryRandomRack = getOneRandomRack(rackSkipSet);
favoredNodes[1] = getOneRandomServer(tertiaryRandomRack);
}
}
return favoredNodes;
}
private ServerName[] singleRackCase(RegionInfo regionInfo,
ServerName primaryRS,
String primaryRack) throws IOException {
// Single rack case: have to pick the secondary and tertiary
// from the same rack
List serverList = getServersFromRack(primaryRack);
if ((serverList == null) || (serverList.size() <= 2)) {
// Single region server case: cannot not place the favored nodes
// on any server;
return null;
} else {
// Randomly select two region servers from the server list and make sure
// they are not overlap with the primary region server;
Set serverSkipSet = new HashSet<>();
serverSkipSet.add(primaryRS);
// Place the secondary RS
ServerName secondaryRS = getOneRandomServer(primaryRack, serverSkipSet);
// Skip the secondary for the tertiary placement
serverSkipSet.add(secondaryRS);
ServerName tertiaryRS = getOneRandomServer(primaryRack, serverSkipSet);
if (secondaryRS == null || tertiaryRS == null) {
LOG.error("Cannot place the secondary, tertiary favored node for region " +
regionInfo.getRegionNameAsString());
}
// Create the secondary and tertiary pair
ServerName[] favoredNodes = new ServerName[2];
favoredNodes[0] = secondaryRS;
favoredNodes[1] = tertiaryRS;
return favoredNodes;
}
}
/**
* Place secondary and tertiary nodes in a multi rack case.
* If there are only two racks, then we try the place the secondary
* and tertiary on different rack than primary. But if the other rack has
* only one region server, then we place primary and tertiary on one rack
* and secondary on another. The aim is two distribute the three favored nodes
* on >= 2 racks.
* TODO: see how we can use generateMissingFavoredNodeMultiRack API here
* @param regionInfo Region for which we are trying to generate FN
* @param primaryRS The primary favored node.
* @param primaryRack The rack of the primary favored node.
* @return Array containing secondary and tertiary favored nodes.
* @throws IOException Signals that an I/O exception has occurred.
*/
private ServerName[] multiRackCase(RegionInfo regionInfo, ServerName primaryRS,
String primaryRack) throws IOException {
ListfavoredNodes = Lists.newArrayList(primaryRS);
// Create the secondary and tertiary pair
ServerName secondaryRS = generateMissingFavoredNodeMultiRack(favoredNodes);
favoredNodes.add(secondaryRS);
String secondaryRack = getRackOfServer(secondaryRS);
ServerName tertiaryRS;
if (primaryRack.equals(secondaryRack)) {
tertiaryRS = generateMissingFavoredNode(favoredNodes);
} else {
// Try to place tertiary in secondary RS rack else place on primary rack.
tertiaryRS = getOneRandomServer(secondaryRack, Sets.newHashSet(secondaryRS));
if (tertiaryRS == null) {
tertiaryRS = getOneRandomServer(primaryRack, Sets.newHashSet(primaryRS));
}
// We couldn't find anything in secondary rack, get any FN
if (tertiaryRS == null) {
tertiaryRS = generateMissingFavoredNode(Lists.newArrayList(primaryRS, secondaryRS));
}
}
return new ServerName[]{ secondaryRS, tertiaryRS };
}
public boolean canPlaceFavoredNodes() {
return (this.servers.size() >= FAVORED_NODES_NUM);
}
private int getTotalNumberOfRacks() {
return this.uniqueRackList.size();
}
private List getServersFromRack(String rack) {
return this.rackToRegionServerMap.get(rack);
}
/**
* Gets a random server from the specified rack and skips anything specified.
* @param rack rack from a server is needed
* @param skipServerSet the server shouldn't belong to this set
*/
protected ServerName getOneRandomServer(String rack, Set skipServerSet) {
// Is the rack valid? Do we recognize it?
if (rack == null || getServersFromRack(rack) == null ||
getServersFromRack(rack).isEmpty()) {
return null;
}
// Lets use a set so we can eliminate duplicates
Set serversToChooseFrom = Sets.newHashSet();
for (ServerName sn : getServersFromRack(rack)) {
serversToChooseFrom.add(StartcodeAgnosticServerName.valueOf(sn));
}
if (skipServerSet != null && skipServerSet.size() > 0) {
for (ServerName sn : skipServerSet) {
serversToChooseFrom.remove(StartcodeAgnosticServerName.valueOf(sn));
}
// Do we have any servers left to choose from?
if (serversToChooseFrom.isEmpty()) {
return null;
}
}
ServerName randomServer = null;
int randomIndex = random.nextInt(serversToChooseFrom.size());
int j = 0;
for (StartcodeAgnosticServerName sn : serversToChooseFrom) {
if (j == randomIndex) {
randomServer = sn;
break;
}
j++;
}
if (randomServer != null) {
return ServerName.valueOf(randomServer.getAddress(), randomServer.getStartcode());
} else {
return null;
}
}
private ServerName getOneRandomServer(String rack) throws IOException {
return this.getOneRandomServer(rack, null);
}
protected String getOneRandomRack(Set skipRackSet) throws IOException {
if (skipRackSet == null || uniqueRackList.size() <= skipRackSet.size()) {
throw new IOException("Cannot randomly pick another random server");
}
String randomRack;
do {
int randomIndex = random.nextInt(this.uniqueRackList.size());
randomRack = this.uniqueRackList.get(randomIndex);
} while (skipRackSet.contains(randomRack));
return randomRack;
}
public static String getFavoredNodesAsString(List nodes) {
StringBuilder strBuf = new StringBuilder();
int i = 0;
for (ServerName node : nodes) {
strBuf.append(node.getAddress());
if (++i != nodes.size()) strBuf.append(";");
}
return strBuf.toString();
}
/*
* Generates a missing favored node based on the input favored nodes. This helps to generate
* new FN when there is already 2 FN and we need a third one. For eg, while generating new FN
* for split daughters after inheriting 2 FN from the parent. If the cluster has only one rack
* it generates from the same rack. If the cluster has multiple racks, then it ensures the new
* FN respects the rack constraints similar to HDFS. For eg: if there are 3 FN, they will be
* spread across 2 racks.
*/
public ServerName generateMissingFavoredNode(List favoredNodes) throws IOException {
if (this.uniqueRackList.size() == 1) {
return generateMissingFavoredNodeSingleRack(favoredNodes, null);
} else {
return generateMissingFavoredNodeMultiRack(favoredNodes, null);
}
}
public ServerName generateMissingFavoredNode(List favoredNodes,
List excludeNodes) throws IOException {
if (this.uniqueRackList.size() == 1) {
return generateMissingFavoredNodeSingleRack(favoredNodes, excludeNodes);
} else {
return generateMissingFavoredNodeMultiRack(favoredNodes, excludeNodes);
}
}
/*
* Generate FN for a single rack scenario, don't generate from one of the excluded nodes. Helps
* when we would like to find a replacement node.
*/
private ServerName generateMissingFavoredNodeSingleRack(List favoredNodes,
List excludeNodes) throws IOException {
ServerName newServer = null;
Set excludeFNSet = Sets.newHashSet(favoredNodes);
if (excludeNodes != null && excludeNodes.size() > 0) {
excludeFNSet.addAll(excludeNodes);
}
if (favoredNodes.size() < FAVORED_NODES_NUM) {
newServer = this.getOneRandomServer(this.uniqueRackList.get(0), excludeFNSet);
}
return newServer;
}
private ServerName generateMissingFavoredNodeMultiRack(List favoredNodes)
throws IOException {
return generateMissingFavoredNodeMultiRack(favoredNodes, null);
}
/*
* Generates a missing FN based on the input favoredNodes and also the nodes to be skipped.
*
* Get the current layout of favored nodes arrangement and nodes to be excluded and get a
* random node that goes with HDFS block placement. Eg: If the existing nodes are on one rack,
* generate one from another rack. We exclude as much as possible so the random selection
* has more chance to generate a node within a few iterations, ideally 1.
*/
private ServerName generateMissingFavoredNodeMultiRack(List favoredNodes,
List excludeNodes) throws IOException {
Set racks = Sets.newHashSet();
Map> rackToFNMapping = new HashMap<>();
// Lets understand the current rack distribution of the FN
for (ServerName sn : favoredNodes) {
String rack = getRackOfServer(sn);
racks.add(rack);
Set serversInRack = rackToFNMapping.get(rack);
if (serversInRack == null) {
serversInRack = Sets.newHashSet();
rackToFNMapping.put(rack, serversInRack);
}
serversInRack.add(sn);
}
// What racks should be skipped while getting a FN?
Set skipRackSet = Sets.newHashSet();
/*
* If both the FN are from the same rack, then we don't want to generate another FN on the
* same rack. If that rack fails, the region would be unavailable.
*/
if (racks.size() == 1 && favoredNodes.size() > 1) {
skipRackSet.add(racks.iterator().next());
}
/*
* If there are no free nodes on the existing racks, we should skip those racks too. We can
* reduce the number of iterations for FN selection.
*/
for (String rack : racks) {
if (getServersFromRack(rack) != null &&
rackToFNMapping.get(rack).size() == getServersFromRack(rack).size()) {
skipRackSet.add(rack);
}
}
Set favoredNodeSet = Sets.newHashSet(favoredNodes);
if (excludeNodes != null && excludeNodes.size() > 0) {
favoredNodeSet.addAll(excludeNodes);
}
/*
* Lets get a random rack by excluding skipRackSet and generate a random FN from that rack.
*/
int i = 0;
Set randomRacks = Sets.newHashSet();
ServerName newServer = null;
do {
String randomRack = this.getOneRandomRack(skipRackSet);
newServer = this.getOneRandomServer(randomRack, favoredNodeSet);
randomRacks.add(randomRack);
i++;
} while ((i < MAX_ATTEMPTS_FN_GENERATION) && (newServer == null));
if (newServer == null) {
if (LOG.isTraceEnabled()) {
LOG.trace(String.format("Unable to generate additional favored nodes for %s after "
+ "considering racks %s and skip rack %s with a unique rack list of %s and rack "
+ "to RS map of %s and RS to rack map of %s",
StringUtils.join(favoredNodes, ","), randomRacks, skipRackSet, uniqueRackList,
rackToRegionServerMap, regionServerToRackMap));
}
throw new IOException(" Unable to generate additional favored nodes for "
+ StringUtils.join(favoredNodes, ","));
}
return newServer;
}
/*
* Generate favored nodes for a region.
*
* Choose a random server as primary and then choose secondary and tertiary FN so its spread
* across two racks.
*/
public List generateFavoredNodes(RegionInfo hri) throws IOException {
List favoredNodesForRegion = new ArrayList<>(FAVORED_NODES_NUM);
ServerName primary = servers.get(random.nextInt(servers.size()));
favoredNodesForRegion.add(ServerName.valueOf(primary.getAddress(), ServerName.NON_STARTCODE));
Map primaryRSMap = new HashMap<>(1);
primaryRSMap.put(hri, primary);
Map secondaryAndTertiaryRSMap =
placeSecondaryAndTertiaryRS(primaryRSMap);
ServerName[] secondaryAndTertiaryNodes = secondaryAndTertiaryRSMap.get(hri);
if (secondaryAndTertiaryNodes != null && secondaryAndTertiaryNodes.length == 2) {
for (ServerName sn : secondaryAndTertiaryNodes) {
favoredNodesForRegion.add(ServerName.valueOf(sn.getAddress(), ServerName.NON_STARTCODE));
}
return favoredNodesForRegion;
} else {
throw new HBaseIOException("Unable to generate secondary and tertiary favored nodes.");
}
}
public Map> generateFavoredNodesRoundRobin(
Map> assignmentMap, List regions)
throws IOException {
if (regions.size() > 0) {
if (canPlaceFavoredNodes()) {
Map primaryRSMap = new HashMap<>();
// Lets try to have an equal distribution for primary favored node
placePrimaryRSAsRoundRobin(assignmentMap, primaryRSMap, regions);
return generateFavoredNodes(primaryRSMap);
} else {
throw new HBaseIOException("Not enough nodes to generate favored nodes");
}
}
return null;
}
/*
* Generate favored nodes for a set of regions when we know where they are currently hosted.
*/
private Map> generateFavoredNodes(
Map primaryRSMap) {
Map> generatedFavNodes = new HashMap<>();
Map secondaryAndTertiaryRSMap =
placeSecondaryAndTertiaryRS(primaryRSMap);
for (Entry entry : primaryRSMap.entrySet()) {
List favoredNodesForRegion = new ArrayList<>(FAVORED_NODES_NUM);
RegionInfo region = entry.getKey();
ServerName primarySN = entry.getValue();
favoredNodesForRegion.add(ServerName.valueOf(primarySN.getHostname(), primarySN.getPort(),
NON_STARTCODE));
ServerName[] secondaryAndTertiaryNodes = secondaryAndTertiaryRSMap.get(region);
if (secondaryAndTertiaryNodes != null) {
favoredNodesForRegion.add(ServerName.valueOf(
secondaryAndTertiaryNodes[0].getHostname(), secondaryAndTertiaryNodes[0].getPort(),
NON_STARTCODE));
favoredNodesForRegion.add(ServerName.valueOf(
secondaryAndTertiaryNodes[1].getHostname(), secondaryAndTertiaryNodes[1].getPort(),
NON_STARTCODE));
}
generatedFavNodes.put(region, favoredNodesForRegion);
}
return generatedFavNodes;
}
/*
* Get the rack of server from local mapping when present, saves lookup by the RackManager.
*/
private String getRackOfServer(ServerName sn) {
if (this.regionServerToRackMap.containsKey(sn.getHostname())) {
return this.regionServerToRackMap.get(sn.getHostname());
} else {
String rack = this.rackManager.getRack(sn);
this.regionServerToRackMap.put(sn.getHostname(), rack);
return rack;
}
}
}
