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Regionserver Groups for HBase
/*
* 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.rsgroup;
import com.google.errorprone.annotations.RestrictedApi;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.TreeMap;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterMetrics;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.constraint.ConstraintException;
import org.apache.hadoop.hbase.master.LoadBalancer;
import org.apache.hadoop.hbase.master.MasterServices;
import org.apache.hadoop.hbase.master.RegionPlan;
import org.apache.hadoop.hbase.master.balancer.LoadBalancerFactory;
import org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer;
import org.apache.hadoop.hbase.net.Address;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.hbase.util.ReflectionUtils;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.collect.ArrayListMultimap;
import org.apache.hbase.thirdparty.com.google.common.collect.ListMultimap;
import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
import org.apache.hbase.thirdparty.com.google.common.collect.Maps;
/**
* GroupBasedLoadBalancer, used when Region Server Grouping is configured (HBase-6721) It does
* region balance based on a table's group membership. Most assignment methods contain two exclusive
* code paths: Online - when the group table is online and Offline - when it is unavailable. During
* Offline, assignments are assigned based on cached information in zookeeper. If unavailable (ie
* bootstrap) then regions are assigned randomly. Once the GROUP table has been assigned, the
* balancer switches to Online and will then start providing appropriate assignments for user
* tables.
*/
@InterfaceAudience.Private
public class RSGroupBasedLoadBalancer implements RSGroupableBalancer {
private static final Logger LOG = LoggerFactory.getLogger(RSGroupBasedLoadBalancer.class);
private MasterServices masterServices;
private volatile RSGroupInfoManager rsGroupInfoManager;
private volatile LoadBalancer internalBalancer;
/**
* Set this key to {@code true} to allow region fallback. Fallback to the default rsgroup first,
* then fallback to any group if no online servers in default rsgroup. Please keep balancer switch
* on at the same time, which is relied on to correct misplaced regions
*/
public static final String FALLBACK_GROUP_ENABLE_KEY = "hbase.rsgroup.fallback.enable";
private volatile boolean fallbackEnabled = false;
/**
* Used by reflection in {@link org.apache.hadoop.hbase.master.balancer.LoadBalancerFactory}.
*/
@InterfaceAudience.Private
public RSGroupBasedLoadBalancer() {
}
// must be called after calling initialize
@Override
public synchronized void updateClusterMetrics(ClusterMetrics sm) {
assert internalBalancer != null;
internalBalancer.updateClusterMetrics(sm);
}
@Override
public synchronized void
updateBalancerLoadInfo(Map>> loadOfAllTable) {
internalBalancer.updateBalancerLoadInfo(loadOfAllTable);
}
public void setMasterServices(MasterServices masterServices) {
this.masterServices = masterServices;
}
@RestrictedApi(explanation = "Should only be called in tests", link = "",
allowedOnPath = ".*/src/test/.*")
public void setRsGroupInfoManager(RSGroupInfoManager rsGroupInfoManager) {
this.rsGroupInfoManager = rsGroupInfoManager;
}
/**
* Balance by RSGroup.
*/
@Override
public synchronized List balanceCluster(
Map>> loadOfAllTable) throws IOException {
if (!isOnline()) {
throw new ConstraintException(
RSGroupInfoManager.RSGROUP_TABLE_NAME + " is not online, unable to perform balance");
}
// Calculate correct assignments and a list of RegionPlan for mis-placed regions
Pair>>,
List> correctedStateAndRegionPlans = correctAssignments(loadOfAllTable);
Map>> correctedLoadOfAllTable =
correctedStateAndRegionPlans.getFirst();
List regionPlans = correctedStateAndRegionPlans.getSecond();
// Add RegionPlan for the regions which have been placed according to the region server group
// assignment into the movement list
try {
// For each rsgroup
for (RSGroupInfo rsgroup : rsGroupInfoManager.listRSGroups()) {
Map>> loadOfTablesInGroup = new HashMap<>();
for (Map.Entry>> entry : correctedLoadOfAllTable
.entrySet()) {
TableName tableName = entry.getKey();
String targetRSGroupName = rsGroupInfoManager.getRSGroupOfTable(tableName);
if (targetRSGroupName == null) {
targetRSGroupName = RSGroupInfo.DEFAULT_GROUP;
}
if (targetRSGroupName.equals(rsgroup.getName())) {
loadOfTablesInGroup.put(tableName, entry.getValue());
}
}
List groupPlans = null;
if (!loadOfTablesInGroup.isEmpty()) {
LOG.info("Start Generate Balance plan for group: " + rsgroup.getName());
groupPlans = this.internalBalancer.balanceCluster(loadOfTablesInGroup);
}
if (groupPlans != null) {
regionPlans.addAll(groupPlans);
}
}
} catch (IOException exp) {
LOG.warn("Exception while balancing cluster.", exp);
regionPlans.clear();
}
return regionPlans;
}
@Override
@NonNull
public Map> roundRobinAssignment(List regions,
List servers) throws HBaseIOException {
Map> assignments = Maps.newHashMap();
List, List>> pairs =
generateGroupAssignments(regions, servers);
for (Pair, List> pair : pairs) {
Map> result =
this.internalBalancer.roundRobinAssignment(pair.getFirst(), pair.getSecond());
result.forEach((server, regionInfos) -> assignments
.computeIfAbsent(server, s -> Lists.newArrayList()).addAll(regionInfos));
}
return assignments;
}
@Override
@NonNull
public Map> retainAssignment(Map regions,
List servers) throws HBaseIOException {
try {
Map> assignments = new TreeMap<>();
List, List>> pairs =
generateGroupAssignments(Lists.newArrayList(regions.keySet()), servers);
for (Pair, List> pair : pairs) {
List regionList = pair.getFirst();
Map currentAssignmentMap = Maps.newTreeMap();
regionList.forEach(r -> currentAssignmentMap.put(r, regions.get(r)));
Map> pairResult =
this.internalBalancer.retainAssignment(currentAssignmentMap, pair.getSecond());
pairResult.forEach((server, rs) -> assignments
.computeIfAbsent(server, s -> Lists.newArrayList()).addAll(rs));
}
return assignments;
} catch (IOException e) {
throw new HBaseIOException("Failed to do online retain assignment", e);
}
}
@Override
public ServerName randomAssignment(RegionInfo region, List servers)
throws HBaseIOException {
List, List>> pairs =
generateGroupAssignments(Lists.newArrayList(region), servers);
List filteredServers = pairs.iterator().next().getSecond();
return this.internalBalancer.randomAssignment(region, filteredServers);
}
private List, List>> generateGroupAssignments(
List regions, List servers) throws HBaseIOException {
try {
ListMultimap regionMap = ArrayListMultimap.create();
ListMultimap serverMap = ArrayListMultimap.create();
RSGroupInfo defaultInfo = rsGroupInfoManager.getRSGroup(RSGroupInfo.DEFAULT_GROUP);
for (RegionInfo region : regions) {
String groupName =
Optional.ofNullable(rsGroupInfoManager.getRSGroupOfTable(region.getTable()))
.orElse(defaultInfo.getName());
regionMap.put(groupName, region);
}
for (String groupKey : regionMap.keySet()) {
RSGroupInfo info = rsGroupInfoManager.getRSGroup(groupKey);
serverMap.putAll(groupKey, filterOfflineServers(info, servers));
}
List, List>> result = Lists.newArrayList();
List fallbackRegions = Lists.newArrayList();
for (String groupKey : regionMap.keySet()) {
if (serverMap.get(groupKey).isEmpty()) {
fallbackRegions.addAll(regionMap.get(groupKey));
} else {
result.add(Pair.newPair(regionMap.get(groupKey), serverMap.get(groupKey)));
}
}
if (!fallbackRegions.isEmpty()) {
List candidates = null;
if (isFallbackEnabled()) {
candidates = getFallBackCandidates(servers);
}
candidates = (candidates == null || candidates.isEmpty())
? Lists.newArrayList(BOGUS_SERVER_NAME)
: candidates;
result.add(Pair.newPair(fallbackRegions, candidates));
}
return result;
} catch (IOException e) {
throw new HBaseIOException("Failed to generate group assignments", e);
}
}
private List filterOfflineServers(RSGroupInfo RSGroupInfo,
List onlineServers) {
if (RSGroupInfo != null) {
return filterServers(RSGroupInfo.getServers(), onlineServers);
} else {
LOG.warn("RSGroup Information found to be null. Some regions might be unassigned.");
return Collections.emptyList();
}
}
/**
* Filter servers based on the online servers.
*
* servers is actually a TreeSet (see {@link org.apache.hadoop.hbase.rsgroup.RSGroupInfo}), having
* its contains()'s time complexity as O(logn), which is good enough.
*
* TODO: consider using HashSet to pursue O(1) for contains() throughout the calling chain if
* needed.
* @param servers the servers
* @param onlineServers List of servers which are online.
* @return the list
*/
private List filterServers(Set servers, List onlineServers) {
ArrayList finalList = new ArrayList<>();
for (ServerName onlineServer : onlineServers) {
if (servers.contains(onlineServer.getAddress())) {
finalList.add(onlineServer);
}
}
return finalList;
}
private Pair>>, List>
correctAssignments(Map>> existingAssignments)
throws IOException {
// To return
Map>> correctAssignments = new HashMap<>();
List regionPlansForMisplacedRegions = new ArrayList<>();
for (Map.Entry>> assignments : existingAssignments
.entrySet()) {
TableName tableName = assignments.getKey();
Map> clusterLoad = assignments.getValue();
Map> correctServerRegion = new TreeMap<>();
RSGroupInfo targetRSGInfo = null;
try {
String groupName = rsGroupInfoManager.getRSGroupOfTable(tableName);
if (groupName == null) {
LOG.debug("Group not found for table " + tableName + ", using default");
groupName = RSGroupInfo.DEFAULT_GROUP;
}
targetRSGInfo = rsGroupInfoManager.getRSGroup(groupName);
} catch (IOException exp) {
LOG.debug("RSGroup information null for region of table " + tableName, exp);
}
for (Map.Entry> serverRegionMap : clusterLoad.entrySet()) {
ServerName currentHostServer = serverRegionMap.getKey();
List regionInfoList = serverRegionMap.getValue();
if (
targetRSGInfo == null || !targetRSGInfo.containsServer(currentHostServer.getAddress())
) {
regionInfoList.forEach(regionInfo -> {
regionPlansForMisplacedRegions.add(new RegionPlan(regionInfo, currentHostServer, null));
});
} else {
correctServerRegion.put(currentHostServer, regionInfoList);
}
}
correctAssignments.put(tableName, correctServerRegion);
}
// Return correct assignments and region movement plan for mis-placed regions together
return new Pair>>, List>(
correctAssignments, regionPlansForMisplacedRegions);
}
@Override
public void initialize() throws HBaseIOException {
try {
if (rsGroupInfoManager == null) {
List cps =
masterServices.getMasterCoprocessorHost().findCoprocessors(RSGroupAdminEndpoint.class);
if (cps.size() != 1) {
String msg = "Expected one implementation of GroupAdminEndpoint but found " + cps.size();
LOG.error(msg);
throw new HBaseIOException(msg);
}
rsGroupInfoManager = cps.get(0).getGroupInfoManager();
if (rsGroupInfoManager == null) {
String msg = "RSGroupInfoManager hasn't been initialized";
LOG.error(msg);
throw new HBaseIOException(msg);
}
rsGroupInfoManager.start();
}
} catch (IOException e) {
throw new HBaseIOException("Failed to initialize GroupInfoManagerImpl", e);
}
Configuration conf = masterServices.getConfiguration();
// Create the balancer
Class balancerClass = conf.getClass(HBASE_RSGROUP_LOADBALANCER_CLASS,
StochasticLoadBalancer.class, LoadBalancer.class);
if (this.getClass().isAssignableFrom(balancerClass)) {
LOG.warn("The internal balancer of RSGroupBasedLoadBalancer cannot be itself, "
+ "falling back to the default LoadBalancer class");
balancerClass = LoadBalancerFactory.getDefaultLoadBalancerClass();
}
internalBalancer = ReflectionUtils.newInstance(balancerClass);
internalBalancer.setMasterServices(masterServices);
internalBalancer.initialize();
// init fallback groups
this.fallbackEnabled = conf.getBoolean(FALLBACK_GROUP_ENABLE_KEY, false);
}
public boolean isOnline() {
if (this.rsGroupInfoManager == null) {
return false;
}
return this.rsGroupInfoManager.isOnline();
}
public boolean isFallbackEnabled() {
return fallbackEnabled;
}
@Override
public void regionOnline(RegionInfo regionInfo, ServerName sn) {
}
@Override
public void regionOffline(RegionInfo regionInfo) {
}
@Override
public synchronized void onConfigurationChange(Configuration conf) {
boolean newFallbackEnabled = conf.getBoolean(FALLBACK_GROUP_ENABLE_KEY, false);
if (fallbackEnabled != newFallbackEnabled) {
LOG.info("Changing the value of {} from {} to {}", FALLBACK_GROUP_ENABLE_KEY, fallbackEnabled,
newFallbackEnabled);
fallbackEnabled = newFallbackEnabled;
}
internalBalancer.onConfigurationChange(conf);
}
@Override
public void stop(String why) {
internalBalancer.stop(why);
}
@Override
public boolean isStopped() {
return internalBalancer.isStopped();
}
@Override
public synchronized void postMasterStartupInitialize() {
this.internalBalancer.postMasterStartupInitialize();
}
public void updateBalancerStatus(boolean status) {
internalBalancer.updateBalancerStatus(status);
}
private List getFallBackCandidates(List servers) {
List serverNames = null;
try {
RSGroupInfo info = rsGroupInfoManager.getRSGroup(RSGroupInfo.DEFAULT_GROUP);
serverNames = filterOfflineServers(info, servers);
} catch (IOException e) {
LOG.error("Failed to get default rsgroup info to fallback", e);
}
return serverNames == null || serverNames.isEmpty() ? servers : serverNames;
}
}