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HBASE-28513 The StochasticLoadBalancer should support discrete evalua…
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Ray Mattingly
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Dec 14, 2024
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...-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerConditionals.java
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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.master.balancer; | ||
|
|
||
| import java.lang.reflect.Constructor; | ||
| import java.util.Collections; | ||
| import java.util.List; | ||
| import java.util.Set; | ||
| import java.util.concurrent.atomic.AtomicInteger; | ||
| import java.util.stream.Collectors; | ||
| import org.apache.hadoop.conf.Configuration; | ||
| import org.apache.hadoop.hbase.master.RegionPlan; | ||
| 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.ImmutableSet; | ||
|
|
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| /** | ||
| * Balancer conditionals supplement cost functions in the {@link StochasticLoadBalancer}. Cost | ||
| * functions are insufficient and difficult to work with when making discrete decisions; this is | ||
| * because they operate on a continuous scale, and each cost function's multiplier affects the | ||
| * relative importance of every other cost function. So it is difficult to meaningfully and clearly | ||
| * value many aspects of your region distribution via cost functions alone. Conditionals allow you | ||
| * to very clearly define discrete rules that your balancer would ideally follow. To clarify, a | ||
| * conditional violation will not block a region assignment because we would prefer to have uptime | ||
| * than have perfectly intentional balance. But conditionals allow you to, for example, define that | ||
| * a region's primary and secondary should not live on the same rack. Another example, conditionals | ||
| * make it easy to define that system tables will ideally be isolated on their own RegionServer. | ||
| */ | ||
| @InterfaceAudience.Private | ||
| public class BalancerConditionals { | ||
|
|
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| private static final Logger LOG = LoggerFactory.getLogger(BalancerConditionals.class); | ||
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| protected static BalancerConditionals INSTANCE = new BalancerConditionals(); | ||
| public static final String ISOLATE_SYSTEM_TABLES_KEY = | ||
| "hbase.master.balancer.stochastic.conditionals.isolateSystemTables"; | ||
| public static final boolean ISOLATE_SYSTEM_TABLES_DEFAULT = false; | ||
|
|
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| public static final String ISOLATE_META_TABLE_KEY = | ||
| "hbase.master.balancer.stochastic.conditionals.isolateMetaTable"; | ||
| public static final boolean ISOLATE_META_TABLE_DEFAULT = false; | ||
|
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| public static final String DISTRIBUTE_REPLICAS_CONDITIONALS_KEY = | ||
| "hbase.master.balancer.stochastic.conditionals.distributeReplicas"; | ||
| public static final boolean DISTRIBUTE_REPLICAS_CONDITIONALS_DEFAULT = false; | ||
|
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| public static final String ADDITIONAL_CONDITIONALS_KEY = | ||
| "hbase.master.balancer.stochastic.additionalConditionals"; | ||
|
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| // when this count is low, we'll be more likely to trigger a subsequent balancer run | ||
| private static final AtomicInteger BALANCE_COUNT_WITHOUT_IMPROVEMENTS = new AtomicInteger(0); | ||
| private static final int BALANCE_COUNT_WITHOUT_IMPROVEMENTS_CEILING = 10; | ||
|
|
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| private Set<Class<? extends RegionPlanConditional>> conditionalClasses = Collections.emptySet(); | ||
| private Set<RegionPlanConditional> conditionals = Collections.emptySet(); | ||
| private Configuration conf; | ||
|
|
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| private BalancerConditionals() { | ||
| } | ||
|
|
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| protected boolean isTableIsolationEnabled() { | ||
| return conditionalClasses.contains(SystemTableIsolationConditional.class) | ||
| || conditionalClasses.contains(MetaTableIsolationConditional.class); | ||
| } | ||
|
|
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| protected boolean shouldRunBalancer() { | ||
| return BALANCE_COUNT_WITHOUT_IMPROVEMENTS.get() < BALANCE_COUNT_WITHOUT_IMPROVEMENTS_CEILING; | ||
| } | ||
|
|
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| protected int getConsecutiveBalancesWithoutImprovement() { | ||
| return BALANCE_COUNT_WITHOUT_IMPROVEMENTS.get(); | ||
| } | ||
|
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| protected void incConsecutiveBalancesWithoutImprovement() { | ||
| if (BALANCE_COUNT_WITHOUT_IMPROVEMENTS.get() == Integer.MAX_VALUE) { | ||
| return; | ||
| } | ||
| this.BALANCE_COUNT_WITHOUT_IMPROVEMENTS.getAndIncrement(); | ||
| LOG.trace("Set balanceCountWithoutImprovements={}", | ||
| this.BALANCE_COUNT_WITHOUT_IMPROVEMENTS.get()); | ||
| } | ||
|
|
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| protected void resetConsecutiveBalancesWithoutImprovement() { | ||
| this.BALANCE_COUNT_WITHOUT_IMPROVEMENTS.set(0); | ||
| LOG.trace("Set balanceCountWithoutImprovements=0"); | ||
| } | ||
|
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| protected Set<Class<? extends RegionPlanConditional>> getConditionalClasses() { | ||
| return Set.copyOf(conditionalClasses); | ||
| } | ||
|
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| protected boolean shouldSkipSloppyServerEvaluation() { | ||
| return conditionals.stream() | ||
| .anyMatch(conditional -> conditional instanceof SystemTableIsolationConditional | ||
| || conditional instanceof MetaTableIsolationConditional); | ||
| } | ||
|
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| protected void loadConf(Configuration conf) { | ||
| this.conf = conf; | ||
| ImmutableSet.Builder<Class<? extends RegionPlanConditional>> conditionalClasses = | ||
| ImmutableSet.builder(); | ||
|
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| boolean isolateSystemTables = | ||
| conf.getBoolean(ISOLATE_SYSTEM_TABLES_KEY, ISOLATE_SYSTEM_TABLES_DEFAULT); | ||
| if (isolateSystemTables) { | ||
| conditionalClasses.add(SystemTableIsolationConditional.class); | ||
| } | ||
|
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| boolean isolateMetaTable = conf.getBoolean(ISOLATE_META_TABLE_KEY, ISOLATE_META_TABLE_DEFAULT); | ||
| if (isolateMetaTable) { | ||
| conditionalClasses.add(MetaTableIsolationConditional.class); | ||
| } | ||
|
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| boolean distributeReplicas = conf.getBoolean(DISTRIBUTE_REPLICAS_CONDITIONALS_KEY, | ||
| DISTRIBUTE_REPLICAS_CONDITIONALS_DEFAULT); | ||
| if (distributeReplicas) { | ||
| conditionalClasses.add(DistributeReplicasConditional.class); | ||
| } | ||
|
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| Class<?>[] classes = conf.getClasses(ADDITIONAL_CONDITIONALS_KEY); | ||
| for (Class<?> clazz : classes) { | ||
| if (!RegionPlanConditional.class.isAssignableFrom(clazz)) { | ||
| LOG.warn("Class {} is not a RegionPlanConditional", clazz.getName()); | ||
| continue; | ||
| } | ||
| conditionalClasses.add(clazz.asSubclass(RegionPlanConditional.class)); | ||
| } | ||
| this.conditionalClasses = conditionalClasses.build(); | ||
| } | ||
|
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| protected void loadClusterState(BalancerClusterState cluster) { | ||
| conditionals = conditionalClasses.stream().map(clazz -> createConditional(clazz, conf, cluster)) | ||
| .collect(Collectors.toSet()); | ||
| } | ||
|
|
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| protected int getConditionalViolationChange(List<RegionPlan> regionPlans) { | ||
| if (conditionals.isEmpty()) { | ||
| incConsecutiveBalancesWithoutImprovement(); | ||
| return 0; | ||
| } | ||
| int conditionalViolationChange = 0; | ||
| for (RegionPlan regionPlan : regionPlans) { | ||
| conditionalViolationChange += getConditionalViolationChange(conditionals, regionPlan); | ||
| } | ||
| return conditionalViolationChange; | ||
| } | ||
|
|
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| private static int getConditionalViolationChange(Set<RegionPlanConditional> conditionals, | ||
| RegionPlan regionPlan) { | ||
| RegionPlan inverseRegionPlan = new RegionPlan(regionPlan.getRegionInfo(), | ||
| regionPlan.getDestination(), regionPlan.getSource()); | ||
| int currentConditionalViolationCount = | ||
| getConditionalViolationCount(conditionals, inverseRegionPlan); | ||
| int newConditionalViolationCount = getConditionalViolationCount(conditionals, regionPlan); | ||
| int violationChange = newConditionalViolationCount - currentConditionalViolationCount; | ||
| if (violationChange < 0) { | ||
| LOG.trace("Should move region {}_{} from {} to {}", regionPlan.getRegionName(), | ||
| regionPlan.getRegionInfo().getReplicaId(), regionPlan.getSource().getServerName(), | ||
| regionPlan.getDestination().getServerName()); | ||
| } | ||
| return violationChange; | ||
| } | ||
|
|
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| private static int getConditionalViolationCount(Set<RegionPlanConditional> conditionals, | ||
| RegionPlan regionPlan) { | ||
| int regionPlanConditionalViolationCount = 0; | ||
| for (RegionPlanConditional regionPlanConditional : conditionals) { | ||
| if (regionPlanConditional.isViolating(regionPlan)) { | ||
| regionPlanConditionalViolationCount++; | ||
| } | ||
| } | ||
| return regionPlanConditionalViolationCount; | ||
| } | ||
|
|
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| private RegionPlanConditional createConditional(Class<? extends RegionPlanConditional> clazz, | ||
| Configuration conf, BalancerClusterState cluster) { | ||
| try { | ||
| Constructor<? extends RegionPlanConditional> ctor = | ||
| clazz.getDeclaredConstructor(Configuration.class, BalancerClusterState.class); | ||
| return ReflectionUtils.instantiate(clazz.getName(), ctor, conf, cluster); | ||
| } catch (NoSuchMethodException e) { | ||
| LOG.warn( | ||
| "Cannot find constructor with Configuration and BalancerClusterState parameters for class '{}': {}", | ||
| clazz.getName(), e.getMessage()); | ||
| } | ||
| return null; | ||
| } | ||
| } |
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