rmdmattingly commented on code in PR #6651: URL: https://github.com/apache/hbase/pull/6651#discussion_r1959655793
########## hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerConditionals.java: ########## @@ -0,0 +1,205 @@ +/* + * 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.Collection; +import java.util.Collections; +import java.util.List; +import java.util.Objects; +import java.util.Set; +import java.util.stream.Collectors; +import org.apache.hadoop.conf.Configurable; +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.hbase.master.RegionPlan; +import org.apache.hadoop.hbase.master.balancer.replicas.ReplicaKeyCache; +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; + +/** + * 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 + * (without needing to manage distinct RegionServer groups). Use of conditionals may cause an + * extremely unbalanced cluster to exceed its max balancer runtime. This is necessary because + * conditional candidate generation is quite expensive, and cutting it off early could prevent us + * from finding a solution. + */ [email protected] +final class BalancerConditionals implements Configurable { Review Comment: What would be the advantage of using Configured vs Configurable? I thought the Configurable java doc described this well: `Something that may be configured with a Configuration.` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
