/**
* 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.master.balancer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;
import java.util.Random;
import java.util.Set;
import java.util.TreeMap;
import java.util.function.Predicate;
import org.apache.commons.lang.NotImplementedException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterStatus;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.HDFSBlocksDistribution;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.ServerLoad;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.RegionReplicaUtil;
import org.apache.hadoop.hbase.master.LoadBalancer;
import org.apache.hadoop.hbase.master.MasterServices;
import org.apache.hadoop.hbase.master.RackManager;
import org.apache.hadoop.hbase.master.RegionPlan;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.Action.Type;
import org.apache.hadoop.hbase.security.access.AccessControlLists;
import org.apache.hadoop.util.StringUtils;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
/**
* The base class for load balancers. It provides functions used by
* {@link org.apache.hadoop.hbase.master.AssignmentManager} to assign regions in the edge cases.
* It doesn't provide an implementation of the actual balancing algorithm.
*/
public abstract class BaseLoadBalancer implements LoadBalancer {
protected static final int MIN_SERVER_BALANCE = 2;
private volatile boolean stopped = false;
private static final List<HRegionInfo> EMPTY_REGION_LIST = new ArrayList<>(0);
static final Predicate<ServerLoad> IDLE_SERVER_PREDICATOR
= load -> load.getNumberOfRegions() == 0;
protected final RegionLocationFinder regionFinder = new RegionLocationFinder();
private static class DefaultRackManager extends RackManager {
@Override
public String getRack(ServerName server) {
return UNKNOWN_RACK;
}
}
/**
* The constructor that uses the basic MetricsBalancer
*/
protected BaseLoadBalancer() {
metricsBalancer = new MetricsBalancer();
}
/**
* This Constructor accepts an instance of MetricsBalancer,
* which will be used instead of creating a new one
*/
protected BaseLoadBalancer(MetricsBalancer metricsBalancer) {
this.metricsBalancer = (metricsBalancer != null) ? metricsBalancer : new MetricsBalancer();
}
/**
* An efficient array based implementation similar to ClusterState for keeping
* the status of the cluster in terms of region assignment and distribution.
* LoadBalancers, such as StochasticLoadBalancer uses this Cluster object because of
* hundreds of thousands of hashmap manipulations are very costly, which is why this
* class uses mostly indexes and arrays.
*
* Cluster tracks a list of unassigned regions, region assignments, and the server
* topology in terms of server names, hostnames and racks.
*/
protected static class Cluster {
ServerName[] servers;
String[] hosts; // ServerName uniquely identifies a region server. multiple RS can run on the same host
String[] racks;
boolean multiServersPerHost = false; // whether or not any host has more than one server
ArrayList<String> tables;
HRegionInfo[] regions;
Deque<BalancerRegionLoad>[] regionLoads;
private RegionLocationFinder regionFinder;
int[][] regionLocations; //regionIndex -> list of serverIndex sorted by locality
int[] serverIndexToHostIndex; //serverIndex -> host index
int[] serverIndexToRackIndex; //serverIndex -> rack index
int[][] regionsPerServer; //serverIndex -> region list
int[][] regionsPerHost; //hostIndex -> list of regions
int[][] regionsPerRack; //rackIndex -> region list
int[][] primariesOfRegionsPerServer; //serverIndex -> sorted list of regions by primary region index
int[][] primariesOfRegionsPerHost; //hostIndex -> sorted list of regions by primary region index
int[][] primariesOfRegionsPerRack; //rackIndex -> sorted list of regions by primary region index
int[][] serversPerHost; //hostIndex -> list of server indexes
int[][] serversPerRack; //rackIndex -> list of server indexes
int[] regionIndexToServerIndex; //regionIndex -> serverIndex
int[] initialRegionIndexToServerIndex; //regionIndex -> serverIndex (initial cluster state)
int[] regionIndexToTableIndex; //regionIndex -> tableIndex
int[][] numRegionsPerServerPerTable; //serverIndex -> tableIndex -> # regions
int[] numMaxRegionsPerTable; //tableIndex -> max number of regions in a single RS
int[] regionIndexToPrimaryIndex; //regionIndex -> regionIndex of the primary
boolean hasRegionReplicas = false; //whether there is regions with replicas
Integer[] serverIndicesSortedByRegionCount;
Integer[] serverIndicesSortedByLocality;
Map<String, Integer> serversToIndex;
Map<String, Integer> hostsToIndex;
Map<String, Integer> racksToIndex;
Map<String, Integer> tablesToIndex;
Map<HRegionInfo, Integer> regionsToIndex;
float[] localityPerServer;
int numServers;
int numHosts;
int numRacks;
int numTables;
int numRegions;
int numMovedRegions = 0; //num moved regions from the initial configuration
Map<ServerName, List<HRegionInfo>> clusterState;
protected final RackManager rackManager;
protected Cluster(
Map<ServerName, List<HRegionInfo>> clusterState,
Map<String, Deque<BalancerRegionLoad>> loads,
RegionLocationFinder regionFinder,
RackManager rackManager) {
this(null, clusterState, loads, regionFinder, rackManager);
}
@SuppressWarnings("unchecked")
protected Cluster(
Collection<HRegionInfo> unassignedRegions,
Map<ServerName, List<HRegionInfo>> clusterState,
Map<String, Deque<BalancerRegionLoad>> loads,
RegionLocationFinder regionFinder,
RackManager rackManager) {
if (unassignedRegions == null) {
unassignedRegions = EMPTY_REGION_LIST;
}
serversToIndex = new HashMap<>();
hostsToIndex = new HashMap<>();
racksToIndex = new HashMap<>();
tablesToIndex = new HashMap<>();
//TODO: We should get the list of tables from master
tables = new ArrayList<>();
this.rackManager = rackManager != null ? rackManager : new DefaultRackManager();
numRegions = 0;
List<List<Integer>> serversPerHostList = new ArrayList<>();
List<List<Integer>> serversPerRackList = new ArrayList<>();
this.clusterState = clusterState;
this.regionFinder = regionFinder;
// Use servername and port as there can be dead servers in this list. We want everything with
// a matching hostname and port to have the same index.
for (ServerName sn : clusterState.keySet()) {
if (serversToIndex.get(sn.getHostAndPort()) == null) {
serversToIndex.put(sn.getHostAndPort(), numServers++);
}
if (!hostsToIndex.containsKey(sn.getHostname())) {
hostsToIndex.put(sn.getHostname(), numHosts++);
serversPerHostList.add(new ArrayList<>(1));
}
int serverIndex = serversToIndex.get(sn.getHostAndPort());
int hostIndex = hostsToIndex.get(sn.getHostname());
serversPerHostList.get(hostIndex).add(serverIndex);
String rack = this.rackManager.getRack(sn);
if (!racksToIndex.containsKey(rack)) {
racksToIndex.put(rack, numRacks++);
serversPerRackList.add(new ArrayList<>());
}
int rackIndex = racksToIndex.get(rack);
serversPerRackList.get(rackIndex).add(serverIndex);
}
// Count how many regions there are.
for (Entry<ServerName, List<HRegionInfo>> entry : clusterState.entrySet()) {
numRegions += entry.getValue().size();
}
numRegions += unassignedRegions.size();
regionsToIndex = new HashMap<>(numRegions);
servers = new ServerName[numServers];
serversPerHost = new int[numHosts][];
serversPerRack = new int[numRacks][];
regions = new HRegionInfo[numRegions];
regionIndexToServerIndex = new int[numRegions];
initialRegionIndexToServerIndex = new int[numRegions];
regionIndexToTableIndex = new int[numRegions];
regionIndexToPrimaryIndex = new int[numRegions];
regionLoads = new Deque[numRegions];
regionLocations = new int[numRegions][];
serverIndicesSortedByRegionCount = new Integer[numServers];
serverIndicesSortedByLocality = new Integer[numServers];
localityPerServer = new float[numServers];
serverIndexToHostIndex = new int[numServers];
serverIndexToRackIndex = new int[numServers];
regionsPerServer = new int[numServers][];
regionsPerHost = new int[numHosts][];
regionsPerRack = new int[numRacks][];
primariesOfRegionsPerServer = new int[numServers][];
primariesOfRegionsPerHost = new int[numHosts][];
primariesOfRegionsPerRack = new int[numRacks][];
int tableIndex = 0, regionIndex = 0, regionPerServerIndex = 0;
for (Entry<ServerName, List<HRegionInfo>> entry : clusterState.entrySet()) {
int serverIndex = serversToIndex.get(entry.getKey().getHostAndPort());
// keep the servername if this is the first server name for this hostname
// or this servername has the newest startcode.
if (servers[serverIndex] == null ||
servers[serverIndex].getStartcode() < entry.getKey().getStartcode()) {
servers[serverIndex] = entry.getKey();
}
if (regionsPerServer[serverIndex] != null) {
// there is another server with the same hostAndPort in ClusterState.
// allocate the array for the total size
regionsPerServer[serverIndex] = new int[entry.getValue().size() + regionsPerServer[serverIndex].length];
} else {
regionsPerServer[serverIndex] = new int[entry.getValue().size()];
}
primariesOfRegionsPerServer[serverIndex] = new int[regionsPerServer[serverIndex].length];
serverIndicesSortedByRegionCount[serverIndex] = serverIndex;
serverIndicesSortedByLocality[serverIndex] = serverIndex;
}
hosts = new String[numHosts];
for (Entry<String, Integer> entry : hostsToIndex.entrySet()) {
hosts[entry.getValue()] = entry.getKey();
}
racks = new String[numRacks];
for (Entry<String, Integer> entry : racksToIndex.entrySet()) {
racks[entry.getValue()] = entry.getKey();
}
for (Entry<ServerName, List<HRegionInfo>> entry : clusterState.entrySet()) {
int serverIndex = serversToIndex.get(entry.getKey().getHostAndPort());
regionPerServerIndex = 0;
int hostIndex = hostsToIndex.get(entry.getKey().getHostname());
serverIndexToHostIndex[serverIndex] = hostIndex;
int rackIndex = racksToIndex.get(this.rackManager.getRack(entry.getKey()));
serverIndexToRackIndex[serverIndex] = rackIndex;
for (HRegionInfo region : entry.getValue()) {
registerRegion(region, regionIndex, serverIndex, loads, regionFinder);
regionsPerServer[serverIndex][regionPerServerIndex++] = regionIndex;
regionIndex++;
}
}
for (HRegionInfo region : unassignedRegions) {
registerRegion(region, regionIndex, -1, loads, regionFinder);
regionIndex++;
}
for (int i = 0; i < serversPerHostList.size(); i++) {
serversPerHost[i] = new int[serversPerHostList.get(i).size()];
for (int j = 0; j < serversPerHost[i].length; j++) {
serversPerHost[i][j] = serversPerHostList.get(i).get(j);
}
if (serversPerHost[i].length > 1) {
multiServersPerHost = true;
}
}
for (int i = 0; i < serversPerRackList.size(); i++) {
serversPerRack[i] = new int[serversPerRackList.get(i).size()];
for (int j = 0; j < serversPerRack[i].length; j++) {
serversPerRack[i][j] = serversPerRackList.get(i).get(j);
}
}
numTables = tables.size();
numRegionsPerServerPerTable = new int[numServers][numTables];
for (int i = 0; i < numServers; i++) {
for (int j = 0; j < numTables; j++) {
numRegionsPerServerPerTable[i][j] = 0;
}
}
for (int i=0; i < regionIndexToServerIndex.length; i++) {
if (regionIndexToServerIndex[i] >= 0) {
numRegionsPerServerPerTable[regionIndexToServerIndex[i]][regionIndexToTableIndex[i]]++;
}
}
numMaxRegionsPerTable = new int[numTables];
for (int serverIndex = 0 ; serverIndex < numRegionsPerServerPerTable.length; serverIndex++) {
for (tableIndex = 0 ; tableIndex < numRegionsPerServerPerTable[serverIndex].length; tableIndex++) {
if (numRegionsPerServerPerTable[serverIndex][tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = numRegionsPerServerPerTable[serverIndex][tableIndex];
}
}
}
for (int i = 0; i < regions.length; i ++) {
HRegionInfo info = regions[i];
if (RegionReplicaUtil.isDefaultReplica(info)) {
regionIndexToPrimaryIndex[i] = i;
} else {
hasRegionReplicas = true;
HRegionInfo primaryInfo = RegionReplicaUtil.getRegionInfoForDefaultReplica(info);
regionIndexToPrimaryIndex[i] =
regionsToIndex.containsKey(primaryInfo) ?
regionsToIndex.get(primaryInfo):
-1;
}
}
for (int i = 0; i < regionsPerServer.length; i++) {
primariesOfRegionsPerServer[i] = new int[regionsPerServer[i].length];
for (int j = 0; j < regionsPerServer[i].length; j++) {
int primaryIndex = regionIndexToPrimaryIndex[regionsPerServer[i][j]];
primariesOfRegionsPerServer[i][j] = primaryIndex;
}
// sort the regions by primaries.
Arrays.sort(primariesOfRegionsPerServer[i]);
}
// compute regionsPerHost
if (multiServersPerHost) {
for (int i = 0 ; i < serversPerHost.length; i++) {
int numRegionsPerHost = 0;
for (int j = 0; j < serversPerHost[i].length; j++) {
numRegionsPerHost += regionsPerServer[serversPerHost[i][j]].length;
}
regionsPerHost[i] = new int[numRegionsPerHost];
primariesOfRegionsPerHost[i] = new int[numRegionsPerHost];
}
for (int i = 0 ; i < serversPerHost.length; i++) {
int numRegionPerHostIndex = 0;
for (int j = 0; j < serversPerHost[i].length; j++) {
for (int k = 0; k < regionsPerServer[serversPerHost[i][j]].length; k++) {
int region = regionsPerServer[serversPerHost[i][j]][k];
regionsPerHost[i][numRegionPerHostIndex] = region;
int primaryIndex = regionIndexToPrimaryIndex[region];
primariesOfRegionsPerHost[i][numRegionPerHostIndex] = primaryIndex;
numRegionPerHostIndex++;
}
}
// sort the regions by primaries.
Arrays.sort(primariesOfRegionsPerHost[i]);
}
}
// compute regionsPerRack
if (numRacks > 1) {
for (int i = 0 ; i < serversPerRack.length; i++) {
int numRegionsPerRack = 0;
for (int j = 0; j < serversPerRack[i].length; j++) {
numRegionsPerRack += regionsPerServer[serversPerRack[i][j]].length;
}
regionsPerRack[i] = new int[numRegionsPerRack];
primariesOfRegionsPerRack[i] = new int[numRegionsPerRack];
}
for (int i = 0 ; i < serversPerRack.length; i++) {
int numRegionPerRackIndex = 0;
for (int j = 0; j < serversPerRack[i].length; j++) {
for (int k = 0; k < regionsPerServer[serversPerRack[i][j]].length; k++) {
int region = regionsPerServer[serversPerRack[i][j]][k];
regionsPerRack[i][numRegionPerRackIndex] = region;
int primaryIndex = regionIndexToPrimaryIndex[region];
primariesOfRegionsPerRack[i][numRegionPerRackIndex] = primaryIndex;
numRegionPerRackIndex++;
}
}
// sort the regions by primaries.
Arrays.sort(primariesOfRegionsPerRack[i]);
}
}
}
/** Helper for Cluster constructor to handle a region */
private void registerRegion(HRegionInfo region, int regionIndex,
int serverIndex, Map<String, Deque<BalancerRegionLoad>> loads,
RegionLocationFinder regionFinder) {
String tableName = region.getTable().getNameAsString();
if (!tablesToIndex.containsKey(tableName)) {
tables.add(tableName);
tablesToIndex.put(tableName, tablesToIndex.size());
}
int tableIndex = tablesToIndex.get(tableName);
regionsToIndex.put(region, regionIndex);
regions[regionIndex] = region;
regionIndexToServerIndex[regionIndex] = serverIndex;
initialRegionIndexToServerIndex[regionIndex] = serverIndex;
regionIndexToTableIndex[regionIndex] = tableIndex;
// region load
if (loads != null) {
Deque<BalancerRegionLoad> rl = loads.get(region.getRegionNameAsString());
// That could have failed if the RegionLoad is using the other regionName
if (rl == null) {
// Try getting the region load using encoded name.
rl = loads.get(region.getEncodedName());
}
regionLoads[regionIndex] = rl;
}
if (regionFinder != null) {
// region location
List<ServerName> loc = regionFinder.getTopBlockLocations(region);
regionLocations[regionIndex] = new int[loc.size()];
for (int i = 0; i < loc.size(); i++) {
regionLocations[regionIndex][i] = loc.get(i) == null ? -1
: (serversToIndex.get(loc.get(i).getHostAndPort()) == null ? -1
: serversToIndex.get(loc.get(i).getHostAndPort()));
}
}
}
/** An action to move or swap a region */
public static class Action {
public static enum Type {
ASSIGN_REGION,
MOVE_REGION,
SWAP_REGIONS,
NULL,
}
public Type type;
public Action (Type type) {this.type = type;}
/** Returns an Action which would undo this action */
public Action undoAction() { return this; }
@Override
public String toString() { return type + ":";}
}
public static class AssignRegionAction extends Action {
public int region;
public int server;
public AssignRegionAction(int region, int server) {
super(Type.ASSIGN_REGION);
this.region = region;
this.server = server;
}
@Override
public Action undoAction() {
// TODO implement this. This action is not being used by the StochasticLB for now
// in case it uses it, we should implement this function.
throw new NotImplementedException();
}
@Override
public String toString() {
return type + ": " + region + ":" + server;
}
}
public static class MoveRegionAction extends Action {
public int region;
public int fromServer;
public int toServer;
public MoveRegionAction(int region, int fromServer, int toServer) {
super(Type.MOVE_REGION);
this.fromServer = fromServer;
this.region = region;
this.toServer = toServer;
}
@Override
public Action undoAction() {
return new MoveRegionAction (region, toServer, fromServer);
}
@Override
public String toString() {
return type + ": " + region + ":" + fromServer + " -> " + toServer;
}
}
public static class SwapRegionsAction extends Action {
public int fromServer;
public int fromRegion;
public int toServer;
public int toRegion;
public SwapRegionsAction(int fromServer, int fromRegion, int toServer, int toRegion) {
super(Type.SWAP_REGIONS);
this.fromServer = fromServer;
this.fromRegion = fromRegion;
this.toServer = toServer;
this.toRegion = toRegion;
}
@Override
public Action undoAction() {
return new SwapRegionsAction (fromServer, toRegion, toServer, fromRegion);
}
@Override
public String toString() {
return type + ": " + fromRegion + ":" + fromServer + " <-> " + toRegion + ":" + toServer;
}
}
@edu.umd.cs.findbugs.annotations.SuppressWarnings(value="NM_FIELD_NAMING_CONVENTION",
justification="Mistake. Too disruptive to change now")
public static final Action NullAction = new Action(Type.NULL);
public void doAction(Action action) {
switch (action.type) {
case NULL: break;
case ASSIGN_REGION:
// FindBugs: Having the assert quietens FB BC_UNCONFIRMED_CAST warnings
assert action instanceof AssignRegionAction: action.getClass();
AssignRegionAction ar = (AssignRegionAction) action;
regionsPerServer[ar.server] = addRegion(regionsPerServer[ar.server], ar.region);
regionMoved(ar.region, -1, ar.server);
break;
case MOVE_REGION:
assert action instanceof MoveRegionAction: action.getClass();
MoveRegionAction mra = (MoveRegionAction) action;
regionsPerServer[mra.fromServer] = removeRegion(regionsPerServer[mra.fromServer], mra.region);
regionsPerServer[mra.toServer] = addRegion(regionsPerServer[mra.toServer], mra.region);
regionMoved(mra.region, mra.fromServer, mra.toServer);
break;
case SWAP_REGIONS:
assert action instanceof SwapRegionsAction: action.getClass();
SwapRegionsAction a = (SwapRegionsAction) action;
regionsPerServer[a.fromServer] = replaceRegion(regionsPerServer[a.fromServer], a.fromRegion, a.toRegion);
regionsPerServer[a.toServer] = replaceRegion(regionsPerServer[a.toServer], a.toRegion, a.fromRegion);
regionMoved(a.fromRegion, a.fromServer, a.toServer);
regionMoved(a.toRegion, a.toServer, a.fromServer);
break;
default:
throw new RuntimeException("Uknown action:" + action.type);
}
}
/**
* Return true if the placement of region on server would lower the availability
* of the region in question
* @param server
* @param region
* @return true or false
*/
boolean wouldLowerAvailability(HRegionInfo regionInfo, ServerName serverName) {
if (!serversToIndex.containsKey(serverName.getHostAndPort())) {
return false; // safeguard against race between cluster.servers and servers from LB method args
}
int server = serversToIndex.get(serverName.getHostAndPort());
int region = regionsToIndex.get(regionInfo);
int primary = regionIndexToPrimaryIndex[region];
// there is a subset relation for server < host < rack
// check server first
if (contains(primariesOfRegionsPerServer[server], primary)) {
// check for whether there are other servers that we can place this region
for (int i = 0; i < primariesOfRegionsPerServer.length; i++) {
if (i != server && !contains(primariesOfRegionsPerServer[i], primary)) {
return true; // meaning there is a better server
}
}
return false; // there is not a better server to place this
}
// check host
if (multiServersPerHost) { // these arrays would only be allocated if we have more than one server per host
int host = serverIndexToHostIndex[server];
if (contains(primariesOfRegionsPerHost[host], primary)) {
// check for whether there are other hosts that we can place this region
for (int i = 0; i < primariesOfRegionsPerHost.length; i++) {
if (i != host && !contains(primariesOfRegionsPerHost[i], primary)) {
return true; // meaning there is a better host
}
}
return false; // there is not a better host to place this
}
}
// check rack
if (numRacks > 1) {
int rack = serverIndexToRackIndex[server];
if (contains(primariesOfRegionsPerRack[rack], primary)) {
// check for whether there are other racks that we can place this region
for (int i = 0; i < primariesOfRegionsPerRack.length; i++) {
if (i != rack && !contains(primariesOfRegionsPerRack[i], primary)) {
return true; // meaning there is a better rack
}
}
return false; // there is not a better rack to place this
}
}
return false;
}
void doAssignRegion(HRegionInfo regionInfo, ServerName serverName) {
if (!serversToIndex.containsKey(serverName.getHostAndPort())) {
return;
}
int server = serversToIndex.get(serverName.getHostAndPort());
int region = regionsToIndex.get(regionInfo);
doAction(new AssignRegionAction(region, server));
}
void regionMoved(int region, int oldServer, int newServer) {
regionIndexToServerIndex[region] = newServer;
if (initialRegionIndexToServerIndex[region] == newServer) {
numMovedRegions--; //region moved back to original location
} else if (oldServer >= 0 && initialRegionIndexToServerIndex[region] == oldServer) {
numMovedRegions++; //region moved from original location
}
int tableIndex = regionIndexToTableIndex[region];
if (oldServer >= 0) {
numRegionsPerServerPerTable[oldServer][tableIndex]--;
}
numRegionsPerServerPerTable[newServer][tableIndex]++;
//check whether this caused maxRegionsPerTable in the new Server to be updated
if (numRegionsPerServerPerTable[newServer][tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = numRegionsPerServerPerTable[newServer][tableIndex];
} else if (oldServer >= 0 && (numRegionsPerServerPerTable[oldServer][tableIndex] + 1)
== numMaxRegionsPerTable[tableIndex]) {
//recompute maxRegionsPerTable since the previous value was coming from the old server
for (int serverIndex = 0 ; serverIndex < numRegionsPerServerPerTable.length; serverIndex++) {
if (numRegionsPerServerPerTable[serverIndex][tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = numRegionsPerServerPerTable[serverIndex][tableIndex];
}
}
}
// update for servers
int primary = regionIndexToPrimaryIndex[region];
if (oldServer >= 0) {
primariesOfRegionsPerServer[oldServer] = removeRegion(
primariesOfRegionsPerServer[oldServer], primary);
}
primariesOfRegionsPerServer[newServer] = addRegionSorted(
primariesOfRegionsPerServer[newServer], primary);
// update for hosts
if (multiServersPerHost) {
int oldHost = oldServer >= 0 ? serverIndexToHostIndex[oldServer] : -1;
int newHost = serverIndexToHostIndex[newServer];
if (newHost != oldHost) {
regionsPerHost[newHost] = addRegion(regionsPerHost[newHost], region);
primariesOfRegionsPerHost[newHost] = addRegionSorted(primariesOfRegionsPerHost[newHost], primary);
if (oldHost >= 0) {
regionsPerHost[oldHost] = removeRegion(regionsPerHost[oldHost], region);
primariesOfRegionsPerHost[oldHost] = removeRegion(
primariesOfRegionsPerHost[oldHost], primary); // will still be sorted
}
}
}
// update for racks
if (numRacks > 1) {
int oldRack = oldServer >= 0 ? serverIndexToRackIndex[oldServer] : -1;
int newRack = serverIndexToRackIndex[newServer];
if (newRack != oldRack) {
regionsPerRack[newRack] = addRegion(regionsPerRack[newRack], region);
primariesOfRegionsPerRack[newRack] = addRegionSorted(primariesOfRegionsPerRack[newRack], primary);
if (oldRack >= 0) {
regionsPerRack[oldRack] = removeRegion(regionsPerRack[oldRack], region);
primariesOfRegionsPerRack[oldRack] = removeRegion(
primariesOfRegionsPerRack[oldRack], primary); // will still be sorted
}
}
}
}
int[] removeRegion(int[] regions, int regionIndex) {
//TODO: this maybe costly. Consider using linked lists
int[] newRegions = new int[regions.length - 1];
int i = 0;
for (i = 0; i < regions.length; i++) {
if (regions[i] == regionIndex) {
break;
}
newRegions[i] = regions[i];
}
System.arraycopy(regions, i+1, newRegions, i, newRegions.length - i);
return newRegions;
}
int[] addRegion(int[] regions, int regionIndex) {
int[] newRegions = new int[regions.length + 1];
System.arraycopy(regions, 0, newRegions, 0, regions.length);
newRegions[newRegions.length - 1] = regionIndex;
return newRegions;
}
int[] addRegionSorted(int[] regions, int regionIndex) {
int[] newRegions = new int[regions.length + 1];
int i = 0;
for (i = 0; i < regions.length; i++) { // find the index to insert
if (regions[i] > regionIndex) {
break;
}
}
System.arraycopy(regions, 0, newRegions, 0, i); // copy first half
System.arraycopy(regions, i, newRegions, i+1, regions.length - i); // copy second half
newRegions[i] = regionIndex;
return newRegions;
}
int[] replaceRegion(int[] regions, int regionIndex, int newRegionIndex) {
int i = 0;
for (i = 0; i < regions.length; i++) {
if (regions[i] == regionIndex) {
regions[i] = newRegionIndex;
break;
}
}
return regions;
}
void sortServersByRegionCount() {
Arrays.sort(serverIndicesSortedByRegionCount, numRegionsComparator);
}
int getNumRegions(int server) {
return regionsPerServer[server].length;
}
boolean contains(int[] arr, int val) {
return Arrays.binarySearch(arr, val) >= 0;
}
private Comparator<Integer> numRegionsComparator = new Comparator<Integer>() {
@Override
public int compare(Integer integer, Integer integer2) {
return Integer.valueOf(getNumRegions(integer)).compareTo(getNumRegions(integer2));
}
};
void sortServersByLocality() {
Arrays.sort(serverIndicesSortedByLocality, localityComparator);
}
float getLocality(int server) {
return localityPerServer[server];
}
private Comparator<Integer> localityComparator = new Comparator<Integer>() {
@Override
public int compare(Integer integer, Integer integer2) {
float locality1 = getLocality(integer);
float locality2 = getLocality(integer2);
if (locality1 < locality2) {
return -1;
} else if (locality1 > locality2) {
return 1;
} else {
return 0;
}
}
};
int getLowestLocalityRegionServer() {
if (regionFinder == null) {
return -1;
} else {
sortServersByLocality();
// We want to find server with non zero regions having lowest locality.
int i = 0;
int lowestLocalityServerIndex = serverIndicesSortedByLocality[i];
while (localityPerServer[lowestLocalityServerIndex] == 0
&& (regionsPerServer[lowestLocalityServerIndex].length == 0)) {
i++;
lowestLocalityServerIndex = serverIndicesSortedByLocality[i];
}
if (LOG.isTraceEnabled()) {
LOG.trace("Lowest locality region server with non zero regions is "
+ servers[lowestLocalityServerIndex].getHostname() + " with locality "
+ localityPerServer[lowestLocalityServerIndex]);
}
return lowestLocalityServerIndex;
}
}
int getLowestLocalityRegionOnServer(int serverIndex) {
if (regionFinder != null) {
float lowestLocality = 1.0f;
int lowestLocalityRegionIndex = -1;
if (regionsPerServer[serverIndex].length == 0) {
// No regions on that region server
return -1;
}
for (int j = 0; j < regionsPerServer[serverIndex].length; j++) {
int regionIndex = regionsPerServer[serverIndex][j];
HDFSBlocksDistribution distribution = regionFinder
.getBlockDistribution(regions[regionIndex]);
float locality = distribution.getBlockLocalityIndex(servers[serverIndex].getHostname());
// skip empty region
if (distribution.getUniqueBlocksTotalWeight() == 0) {
continue;
}
if (locality < lowestLocality) {
lowestLocality = locality;
lowestLocalityRegionIndex = j;
}
}
if (lowestLocalityRegionIndex == -1) {
return -1;
}
if (LOG.isTraceEnabled()) {
LOG.trace("Lowest locality region is "
+ regions[regionsPerServer[serverIndex][lowestLocalityRegionIndex]]
.getRegionNameAsString() + " with locality " + lowestLocality
+ " and its region server contains " + regionsPerServer[serverIndex].length
+ " regions");
}
return regionsPerServer[serverIndex][lowestLocalityRegionIndex];
} else {
return -1;
}
}
float getLocalityOfRegion(int region, int server) {
if (regionFinder != null) {
HDFSBlocksDistribution distribution = regionFinder.getBlockDistribution(regions[region]);
return distribution.getBlockLocalityIndex(servers[server].getHostname());
} else {
return 0f;
}
}
/**
* Returns a least loaded server which has better locality for this region
* than the current server.
*/
int getLeastLoadedTopServerForRegion(int region, int currentServer) {
if (regionFinder != null) {
List<ServerName> topLocalServers = regionFinder.getTopBlockLocations(regions[region],
servers[currentServer].getHostname());
int leastLoadedServerIndex = -1;
int load = Integer.MAX_VALUE;
for (ServerName sn : topLocalServers) {
if (!serversToIndex.containsKey(sn.getHostAndPort())) {
continue;
}
int index = serversToIndex.get(sn.getHostAndPort());
if (regionsPerServer[index] == null) {
continue;
}
int tempLoad = regionsPerServer[index].length;
if (tempLoad <= load) {
leastLoadedServerIndex = index;
load = tempLoad;
}
}
if (leastLoadedServerIndex != -1) {
LOG.debug("Pick the least loaded server " + servers[leastLoadedServerIndex].getHostname()
+ " with better locality for region " + regions[region]);
}
return leastLoadedServerIndex;
} else {
return -1;
}
}
void calculateRegionServerLocalities() {
if (regionFinder == null) {
LOG.warn("Region location finder found null, skipping locality calculations.");
return;
}
for (int i = 0; i < regionsPerServer.length; i++) {
HDFSBlocksDistribution distribution = new HDFSBlocksDistribution();
if (regionsPerServer[i].length > 0) {
for (int j = 0; j < regionsPerServer[i].length; j++) {
int regionIndex = regionsPerServer[i][j];
distribution.add(regionFinder.getBlockDistribution(regions[regionIndex]));
}
} else {
LOG.debug("Server " + servers[i].getHostname() + " had 0 regions.");
}
localityPerServer[i] = distribution.getBlockLocalityIndex(servers[i].getHostname());
}
}
@VisibleForTesting
protected void setNumRegions(int numRegions) {
this.numRegions = numRegions;
}
@VisibleForTesting
protected void setNumMovedRegions(int numMovedRegions) {
this.numMovedRegions = numMovedRegions;
}
@edu.umd.cs.findbugs.annotations.SuppressWarnings(value="SBSC_USE_STRINGBUFFER_CONCATENATION",
justification="Not important but should be fixed")
@Override
public String toString() {
String desc = "Cluster{" +
"servers=[";
for(ServerName sn:servers) {
desc += sn.getHostAndPort() + ", ";
}
desc +=
", serverIndicesSortedByRegionCount="+
Arrays.toString(serverIndicesSortedByRegionCount) +
", regionsPerServer=[";
for (int[]r:regionsPerServer) {
desc += Arrays.toString(r);
}
desc += "]" +
", numMaxRegionsPerTable=" +
Arrays.toString(numMaxRegionsPerTable) +
", numRegions=" +
numRegions +
", numServers=" +
numServers +
", numTables=" +
numTables +
", numMovedRegions=" +
numMovedRegions +
'}';
return desc;
}
}
// slop for regions
protected float slop;
// overallSlop to controll simpleLoadBalancer's cluster level threshold
protected float overallSlop;
protected Configuration config;
protected RackManager rackManager;
private static final Random RANDOM = new Random(System.currentTimeMillis());
private static final Log LOG = LogFactory.getLog(BaseLoadBalancer.class);
// Regions of these tables are put on the master by default.
private static final String[] DEFAULT_TABLES_ON_MASTER =
new String[] {AccessControlLists.ACL_TABLE_NAME.getNameAsString(),
TableName.NAMESPACE_TABLE_NAME.getNameAsString(),
TableName.META_TABLE_NAME.getNameAsString()};
public static final String TABLES_ON_MASTER =
"hbase.balancer.tablesOnMaster";
protected final Set<String> tablesOnMaster = new HashSet<>();
protected MetricsBalancer metricsBalancer = null;
protected ClusterStatus clusterStatus = null;
protected ServerName masterServerName;
protected MasterServices services;
/**
* By default, regions of some small system tables such as meta,
* namespace, and acl are assigned to the active master. If you don't
* want to assign any region to the active master, you need to
* configure "hbase.balancer.tablesOnMaster" to "none".
*/
protected static String[] getTablesOnMaster(Configuration conf) {
String valueString = conf.get(TABLES_ON_MASTER);
if (valueString == null) {
return DEFAULT_TABLES_ON_MASTER;
}
valueString = valueString.trim();
if (valueString.equalsIgnoreCase("none")) {
return null;
}
return StringUtils.getStrings(valueString);
}
/**
* Check if configured to put any tables on the active master
*/
public static boolean tablesOnMaster(Configuration conf) {
String[] tables = getTablesOnMaster(conf);
return tables != null && tables.length > 0;
}
public static boolean userTablesOnMaster(Configuration conf) {
String[] tables = getTablesOnMaster(conf);
if (tables == null || tables.length == 0) {
return false;
}
for (String tn:tables) {
if (!tn.startsWith("hbase:")) {
return true;
}
}
return false;
}
@Override
public void setConf(Configuration conf) {
setSlop(conf);
if (slop < 0) slop = 0;
else if (slop > 1) slop = 1;
if (overallSlop < 0) overallSlop = 0;
else if (overallSlop > 1) overallSlop = 1;
this.config = conf;
String[] tables = getTablesOnMaster(conf);
if (tables != null && tables.length > 0) {
Collections.addAll(tablesOnMaster, tables);
}
this.rackManager = new RackManager(getConf());
regionFinder.setConf(conf);
}
protected void setSlop(Configuration conf) {
this.slop = conf.getFloat("hbase.regions.slop", (float) 0.2);
this.overallSlop = conf.getFloat("hbase.regions.overallSlop", slop);
}
/**
* Check if a region belongs to some small system table.
* If so, the primary replica may be expected to be put on the master regionserver.
*/
public boolean shouldBeOnMaster(HRegionInfo region) {
return tablesOnMaster.contains(region.getTable().getNameAsString())
&& region.getReplicaId() == HRegionInfo.DEFAULT_REPLICA_ID;
}
/**
* Balance the regions that should be on master regionserver.
*/
protected List<RegionPlan> balanceMasterRegions(
Map<ServerName, List<HRegionInfo>> clusterMap) {
if (masterServerName == null
|| clusterMap == null || clusterMap.size() <= 1) return null;
List<RegionPlan> plans = null;
List<HRegionInfo> regions = clusterMap.get(masterServerName);
if (regions != null) {
Iterator<ServerName> keyIt = null;
for (HRegionInfo region: regions) {
if (shouldBeOnMaster(region)) continue;
// Find a non-master regionserver to host the region
if (keyIt == null || !keyIt.hasNext()) {
keyIt = clusterMap.keySet().iterator();
}
ServerName dest = keyIt.next();
if (masterServerName.equals(dest)) {
if (!keyIt.hasNext()) {
keyIt = clusterMap.keySet().iterator();
}
dest = keyIt.next();
}
// Move this region away from the master regionserver
RegionPlan plan = new RegionPlan(region, masterServerName, dest);
if (plans == null) {
plans = new ArrayList<>();
}
plans.add(plan);
}
}
for (Map.Entry<ServerName, List<HRegionInfo>> server: clusterMap.entrySet()) {
if (masterServerName.equals(server.getKey())) continue;
for (HRegionInfo region: server.getValue()) {
if (!shouldBeOnMaster(region)) continue;
// Move this region to the master regionserver
RegionPlan plan = new RegionPlan(region, server.getKey(), masterServerName);
if (plans == null) {
plans = new ArrayList<>();
}
plans.add(plan);
}
}
return plans;
}
/**
* Assign the regions that should be on master regionserver.
*/
protected Map<ServerName, List<HRegionInfo>> assignMasterRegions(
Collection<HRegionInfo> regions, List<ServerName> servers) {
if (servers == null || regions == null || regions.isEmpty()) {
return null;
}
Map<ServerName, List<HRegionInfo>> assignments = new TreeMap<>();
if (masterServerName != null && servers.contains(masterServerName)) {
assignments.put(masterServerName, new ArrayList<>());
for (HRegionInfo region: regions) {
if (shouldBeOnMaster(region)) {
assignments.get(masterServerName).add(region);
}
}
}
return assignments;
}
@Override
public Configuration getConf() {
return this.config;
}
@Override
public synchronized void setClusterStatus(ClusterStatus st) {
this.clusterStatus = st;
regionFinder.setClusterStatus(st);
}
@Override
public void setClusterLoad(Map<TableName, Map<ServerName, List<HRegionInfo>>> clusterLoad){
}
@Override
public void setMasterServices(MasterServices masterServices) {
masterServerName = masterServices.getServerName();
this.services = masterServices;
this.regionFinder.setServices(masterServices);
}
public void setRackManager(RackManager rackManager) {
this.rackManager = rackManager;
}
protected boolean needsBalance(Cluster c) {
ClusterLoadState cs = new ClusterLoadState(c.clusterState);
if (cs.getNumServers() < MIN_SERVER_BALANCE) {
if (LOG.isDebugEnabled()) {
LOG.debug("Not running balancer because only " + cs.getNumServers()
+ " active regionserver(s)");
}
return false;
}
if(areSomeRegionReplicasColocated(c)) return true;
// Check if we even need to do any load balancing
// HBASE-3681 check sloppiness first
float average = cs.getLoadAverage(); // for logging
int floor = (int) Math.floor(average * (1 - slop));
int ceiling = (int) Math.ceil(average * (1 + slop));
if (!(cs.getMaxLoad() > ceiling || cs.getMinLoad() < floor)) {
NavigableMap<ServerAndLoad, List<HRegionInfo>> serversByLoad = cs.getServersByLoad();
if (LOG.isTraceEnabled()) {
// If nothing to balance, then don't say anything unless trace-level logging.
LOG.trace("Skipping load balancing because balanced cluster; " +
"servers=" + cs.getNumServers() +
" regions=" + cs.getNumRegions() + " average=" + average +
" mostloaded=" + serversByLoad.lastKey().getLoad() +
" leastloaded=" + serversByLoad.firstKey().getLoad());
}
return false;
}
return true;
}
/**
* Subclasses should implement this to return true if the cluster has nodes that hosts
* multiple replicas for the same region, or, if there are multiple racks and the same
* rack hosts replicas of the same region
* @param c Cluster information
* @return whether region replicas are currently co-located
*/
protected boolean areSomeRegionReplicasColocated(Cluster c) {
return false;
}
/**
* Generates a bulk assignment plan to be used on cluster startup using a
* simple round-robin assignment.
* <p>
* Takes a list of all the regions and all the servers in the cluster and
* returns a map of each server to the regions that it should be assigned.
* <p>
* Currently implemented as a round-robin assignment. Same invariant as load
* balancing, all servers holding floor(avg) or ceiling(avg).
*
* TODO: Use block locations from HDFS to place regions with their blocks
*
* @param regions all regions
* @param servers all servers
* @return map of server to the regions it should take, or null if no
* assignment is possible (ie. no regions or no servers)
*/
@Override
public Map<ServerName, List<HRegionInfo>> roundRobinAssignment(List<HRegionInfo> regions,
List<ServerName> servers) throws HBaseIOException {
metricsBalancer.incrMiscInvocations();
Map<ServerName, List<HRegionInfo>> assignments = assignMasterRegions(regions, servers);
if (assignments != null && !assignments.isEmpty()) {
servers = new ArrayList<>(servers);
// Guarantee not to put other regions on master
servers.remove(masterServerName);
List<HRegionInfo> masterRegions = assignments.get(masterServerName);
if (!masterRegions.isEmpty()) {
regions = new ArrayList<>(regions);
for (HRegionInfo region: masterRegions) {
regions.remove(region);
}
}
}
if (regions == null || regions.isEmpty()) {
return assignments;
}
int numServers = servers == null ? 0 : servers.size();
if (numServers == 0) {
LOG.warn("Wanted to do round robin assignment but no servers to assign to");
return null;
}
// TODO: instead of retainAssignment() and roundRobinAssignment(), we should just run the
// normal LB.balancerCluster() with unassignedRegions. We only need to have a candidate
// generator for AssignRegionAction. The LB will ensure the regions are mostly local
// and balanced. This should also run fast with fewer number of iterations.
if (numServers == 1) { // Only one server, nothing fancy we can do here
ServerName server = servers.get(0);
assignments.put(server, new ArrayList<>(regions));
return assignments;
}
Cluster cluster = createCluster(servers, regions, false);
List<HRegionInfo> unassignedRegions = new ArrayList<>();
roundRobinAssignment(cluster, regions, unassignedRegions,
servers, assignments);
List<HRegionInfo> lastFewRegions = new ArrayList<>();
// assign the remaining by going through the list and try to assign to servers one-by-one
int serverIdx = RANDOM.nextInt(numServers);
for (HRegionInfo region : unassignedRegions) {
boolean assigned = false;
for (int j = 0; j < numServers; j++) { // try all servers one by one
ServerName serverName = servers.get((j + serverIdx) % numServers);
if (!cluster.wouldLowerAvailability(region, serverName)) {
List<HRegionInfo> serverRegions = assignments.get(serverName);
if (serverRegions == null) {
serverRegions = new ArrayList<>();
assignments.put(serverName, serverRegions);
}
serverRegions.add(region);
cluster.doAssignRegion(region, serverName);
serverIdx = (j + serverIdx + 1) % numServers; //remain from next server
assigned = true;
break;
}
}
if (!assigned) {
lastFewRegions.add(region);
}
}
// just sprinkle the rest of the regions on random regionservers. The balanceCluster will
// make it optimal later. we can end up with this if numReplicas > numServers.
for (HRegionInfo region : lastFewRegions) {
int i = RANDOM.nextInt(numServers);
ServerName server = servers.get(i);
List<HRegionInfo> serverRegions = assignments.get(server);
if (serverRegions == null) {
serverRegions = new ArrayList<>();
assignments.put(server, serverRegions);
}
serverRegions.add(region);
cluster.doAssignRegion(region, server);
}
return assignments;
}
protected Cluster createCluster(List<ServerName> servers,
Collection<HRegionInfo> regions, boolean forceRefresh) {
if (forceRefresh == true) {
regionFinder.refreshAndWait(regions);
}
// Get the snapshot of the current assignments for the regions in question, and then create
// a cluster out of it. Note that we might have replicas already assigned to some servers
// earlier. So we want to get the snapshot to see those assignments, but this will only contain
// replicas of the regions that are passed (for performance).
Map<ServerName, List<HRegionInfo>> clusterState = getRegionAssignmentsByServer(regions);
for (ServerName server : servers) {
if (!clusterState.containsKey(server)) {
clusterState.put(server, EMPTY_REGION_LIST);
}
}
return new Cluster(regions, clusterState, null, this.regionFinder,
rackManager);
}
private List<ServerName> findIdleServers(List<ServerName> servers) {
return this.services.getServerManager()
.getOnlineServersListWithPredicator(servers, IDLE_SERVER_PREDICATOR);
}
/**
* Used to assign a single region to a random server.
*/
@Override
public ServerName randomAssignment(HRegionInfo regionInfo, List<ServerName> servers)
throws HBaseIOException {
metricsBalancer.incrMiscInvocations();
if (servers != null && servers.contains(masterServerName)) {
if (shouldBeOnMaster(regionInfo)) {
return masterServerName;
}
servers = new ArrayList<>(servers);
// Guarantee not to put other regions on master
servers.remove(masterServerName);
}
int numServers = servers == null ? 0 : servers.size();
if (numServers == 0) {
LOG.warn("Wanted to retain assignment but no servers to assign to");
return null;
}
if (numServers == 1) { // Only one server, nothing fancy we can do here
return servers.get(0);
}
List<ServerName> idleServers = findIdleServers(servers);
if (idleServers.size() == 1) {
return idleServers.get(0);
}
final List<ServerName> finalServers = idleServers.isEmpty() ?
servers : idleServers;
List<HRegionInfo> regions = Lists.newArrayList(regionInfo);
Cluster cluster = createCluster(finalServers, regions, false);
return randomAssignment(cluster, regionInfo, finalServers);
}
/**
* Generates a bulk assignment startup plan, attempting to reuse the existing
* assignment information from META, but adjusting for the specified list of
* available/online servers available for assignment.
* <p>
* Takes a map of all regions to their existing assignment from META. Also
* takes a list of online servers for regions to be assigned to. Attempts to
* retain all assignment, so in some instances initial assignment will not be
* completely balanced.
* <p>
* Any leftover regions without an existing server to be assigned to will be
* assigned randomly to available servers.
*
* @param regions regions and existing assignment from meta
* @param servers available servers
* @return map of servers and regions to be assigned to them
*/
@Override
public Map<ServerName, List<HRegionInfo>> retainAssignment(Map<HRegionInfo, ServerName> regions,
List<ServerName> servers) throws HBaseIOException {
// Update metrics
metricsBalancer.incrMiscInvocations();
Map<ServerName, List<HRegionInfo>> assignments
= assignMasterRegions(regions.keySet(), servers);
if (assignments != null && !assignments.isEmpty()) {
servers = new ArrayList<>(servers);
// Guarantee not to put other regions on master
servers.remove(masterServerName);
List<HRegionInfo> masterRegions = assignments.get(masterServerName);
if (!masterRegions.isEmpty()) {
regions = new HashMap<>(regions);
for (HRegionInfo region: masterRegions) {
regions.remove(region);
}
}
}
if (regions == null || regions.isEmpty()) {
return assignments;
}
int numServers = servers == null ? 0 : servers.size();
if (numServers == 0) {
LOG.warn("Wanted to do retain assignment but no servers to assign to");
return null;
}
if (numServers == 1) { // Only one server, nothing fancy we can do here
ServerName server = servers.get(0);
assignments.put(server, new ArrayList<>(regions.keySet()));
return assignments;
}
// Group all of the old assignments by their hostname.
// We can't group directly by ServerName since the servers all have
// new start-codes.
// Group the servers by their hostname. It's possible we have multiple
// servers on the same host on different ports.
ArrayListMultimap<String, ServerName> serversByHostname = ArrayListMultimap.create();
for (ServerName server : servers) {
assignments.put(server, new ArrayList<>());
serversByHostname.put(server.getHostname(), server);
}
// Collection of the hostnames that used to have regions
// assigned, but for which we no longer have any RS running
// after the cluster restart.
Set<String> oldHostsNoLongerPresent = Sets.newTreeSet();
int numRandomAssignments = 0;
int numRetainedAssigments = 0;
Cluster cluster = createCluster(servers, regions.keySet(), true);
for (Map.Entry<HRegionInfo, ServerName> entry : regions.entrySet()) {
HRegionInfo region = entry.getKey();
ServerName oldServerName = entry.getValue();
List<ServerName> localServers = new ArrayList<>();
if (oldServerName != null) {
localServers = serversByHostname.get(oldServerName.getHostname());
}
if (localServers.isEmpty()) {
// No servers on the new cluster match up with this hostname,
// assign randomly.
ServerName randomServer = randomAssignment(cluster, region, servers);
assignments.get(randomServer).add(region);
numRandomAssignments++;
if (oldServerName != null) oldHostsNoLongerPresent.add(oldServerName.getHostname());
} else if (localServers.size() == 1) {
// the usual case - one new server on same host
ServerName target = localServers.get(0);
assignments.get(target).add(region);
cluster.doAssignRegion(region, target);
numRetainedAssigments++;
} else {
// multiple new servers in the cluster on this same host
if (localServers.contains(oldServerName)) {
assignments.get(oldServerName).add(region);
cluster.doAssignRegion(region, oldServerName);
} else {
ServerName target = null;
for (ServerName tmp: localServers) {
if (tmp.getPort() == oldServerName.getPort()) {
target = tmp;
break;
}
}
if (target == null) {
target = randomAssignment(cluster, region, localServers);
}
assignments.get(target).add(region);
}
numRetainedAssigments++;
}
}
String randomAssignMsg = "";
if (numRandomAssignments > 0) {
randomAssignMsg =
numRandomAssignments + " regions were assigned "
+ "to random hosts, since the old hosts for these regions are no "
+ "longer present in the cluster. These hosts were:\n "
+ Joiner.on("\n ").join(oldHostsNoLongerPresent);
}
LOG.info("Reassigned " + regions.size() + " regions. " + numRetainedAssigments
+ " retained the pre-restart assignment. " + randomAssignMsg);
return assignments;
}
@Override
public void initialize() throws HBaseIOException{
}
@Override
public void regionOnline(HRegionInfo regionInfo, ServerName sn) {
}
@Override
public void regionOffline(HRegionInfo regionInfo) {
}
@Override
public boolean isStopped() {
return stopped;
}
@Override
public void stop(String why) {
LOG.info("Load Balancer stop requested: "+why);
stopped = true;
}
/**
* Used to assign a single region to a random server.
*/
private ServerName randomAssignment(Cluster cluster, HRegionInfo regionInfo,
List<ServerName> servers) {
int numServers = servers.size(); // servers is not null, numServers > 1
ServerName sn = null;
final int maxIterations = numServers * 4;
int iterations = 0;
do {
int i = RANDOM.nextInt(numServers);
sn = servers.get(i);
} while (cluster.wouldLowerAvailability(regionInfo, sn)
&& iterations++ < maxIterations);
cluster.doAssignRegion(regionInfo, sn);
return sn;
}
/**
* Round robin a list of regions to a list of servers
*/
private void roundRobinAssignment(Cluster cluster, List<HRegionInfo> regions,
List<HRegionInfo> unassignedRegions, List<ServerName> servers,
Map<ServerName, List<HRegionInfo>> assignments) {
int numServers = servers.size();
int numRegions = regions.size();
int max = (int) Math.ceil((float) numRegions / numServers);
int serverIdx = 0;
if (numServers > 1) {
serverIdx = RANDOM.nextInt(numServers);
}
int regionIdx = 0;
for (int j = 0; j < numServers; j++) {
ServerName server = servers.get((j + serverIdx) % numServers);
List<HRegionInfo> serverRegions = new ArrayList<>(max);
for (int i = regionIdx; i < numRegions; i += numServers) {
HRegionInfo region = regions.get(i % numRegions);
if (cluster.wouldLowerAvailability(region, server)) {
unassignedRegions.add(region);
} else {
serverRegions.add(region);
cluster.doAssignRegion(region, server);
}
}
assignments.put(server, serverRegions);
regionIdx++;
}
}
protected Map<ServerName, List<HRegionInfo>> getRegionAssignmentsByServer(
Collection<HRegionInfo> regions) {
if (this.services != null && this.services.getAssignmentManager() != null) {
return this.services.getAssignmentManager().getSnapShotOfAssignment(regions);
} else {
return new HashMap<>();
}
}
@Override
public void onConfigurationChange(Configuration conf) {
}
}