junrao commented on a change in pull request #10753: URL: https://github.com/apache/kafka/pull/10753#discussion_r670647614
########## File path: metadata/src/main/java/org/apache/kafka/controller/PartitionChangeBuilder.java ########## @@ -0,0 +1,243 @@ +/* + * 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.kafka.controller; + +import org.apache.kafka.common.Uuid; +import org.apache.kafka.common.metadata.PartitionChangeRecord; +import org.apache.kafka.metadata.PartitionRegistration; +import org.apache.kafka.metadata.Replicas; +import org.apache.kafka.server.common.ApiMessageAndVersion; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.Optional; +import java.util.function.Function; +import java.util.function.Supplier; + +import static org.apache.kafka.common.metadata.MetadataRecordType.PARTITION_CHANGE_RECORD; +import static org.apache.kafka.metadata.LeaderConstants.NO_LEADER; +import static org.apache.kafka.metadata.LeaderConstants.NO_LEADER_CHANGE; + +/** + * PartitionChangeBuilder handles changing partition registrations. + */ +public class PartitionChangeBuilder { + public static boolean changeRecordIsNoOp(PartitionChangeRecord record) { + if (record.isr() != null) return false; + if (record.leader() != NO_LEADER_CHANGE) return false; + if (record.replicas() != null) return false; + if (record.removingReplicas() != null) return false; + if (record.addingReplicas() != null) return false; + return true; + } + + private final PartitionRegistration partition; + private final Uuid topicId; + private final int partitionId; + private final Function<Integer, Boolean> isAcceptableLeader; + private final Supplier<Boolean> uncleanElectionOk; + private List<Integer> targetIsr; + private List<Integer> targetReplicas; + private List<Integer> targetRemoving; + private List<Integer> targetAdding; + private boolean alwaysElectPreferredIfPossible; + + public PartitionChangeBuilder(PartitionRegistration partition, + Uuid topicId, + int partitionId, + Function<Integer, Boolean> isAcceptableLeader, + Supplier<Boolean> uncleanElectionOk) { + this.partition = partition; + this.topicId = topicId; + this.partitionId = partitionId; + this.isAcceptableLeader = isAcceptableLeader; + this.uncleanElectionOk = uncleanElectionOk; + this.targetIsr = Replicas.toList(partition.isr); + this.targetReplicas = Replicas.toList(partition.replicas); + this.targetRemoving = Replicas.toList(partition.removingReplicas); + this.targetAdding = Replicas.toList(partition.addingReplicas); + this.alwaysElectPreferredIfPossible = false; + } + + public PartitionChangeBuilder setTargetIsr(List<Integer> targetIsr) { + this.targetIsr = targetIsr; + return this; + } + + public PartitionChangeBuilder setTargetReplicas(List<Integer> targetReplicas) { + this.targetReplicas = targetReplicas; + return this; + } + + public PartitionChangeBuilder setAlwaysElectPreferredIfPossible(boolean alwaysElectPreferredIfPossible) { + this.alwaysElectPreferredIfPossible = alwaysElectPreferredIfPossible; + return this; + } + + public PartitionChangeBuilder setTargetRemoving(List<Integer> targetRemoving) { + this.targetRemoving = targetRemoving; + return this; + } + + public PartitionChangeBuilder setTargetAdding(List<Integer> targetAdding) { + this.targetAdding = targetAdding; + return this; + } + + boolean shouldTryElection() { + // If the new isr doesn't have the current leader, we need to try to elect a new + // one. Note: this also handles the case where the current leader is NO_LEADER, + // since that value cannot appear in targetIsr. + if (!targetIsr.contains(partition.leader)) return true; + + // Check if we want to try to get away from a non-preferred leader. + if (alwaysElectPreferredIfPossible && !partition.hasPreferredLeader()) return true; + + return false; + } + + class BestLeader { + final int node; + final boolean unclean; + + BestLeader() { + for (int replica : targetReplicas) { + if (targetIsr.contains(replica) && isAcceptableLeader.apply(replica)) { + this.node = replica; + this.unclean = false; + return; + } + } + if (uncleanElectionOk.get()) { + for (int replica : targetReplicas) { + if (isAcceptableLeader.apply(replica)) { + this.node = replica; + this.unclean = true; + return; + } + } + } + this.node = NO_LEADER; + this.unclean = false; + } + } + + private void tryElection(PartitionChangeRecord record) { + BestLeader bestLeader = new BestLeader(); + if (bestLeader.node != partition.leader) { + record.setLeader(bestLeader.node); + if (bestLeader.unclean) { + // If the election was unclean, we have to forcibly set the ISR to just the + // new leader. This can result in data loss! + record.setIsr(Collections.singletonList(bestLeader.node)); + } + } + } + + /** + * Trigger a leader epoch bump if one is needed. + * + * We need to bump the leader epoch if: + * 1. The leader changed. + * 2. The new ISR does not contain all the nodes that the old ISR did. + * 3. The new replia list does not contain all the nodes that the old replia list did. + * + * Changes that do NOT fall in these categories will increase the partition epoch, but + * not the leader epoch. Note that if the leader epoch increases, the partition epoch + * will always increases as well; there is no case where the partition epoch increases Review comment: increases => increase -- 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. 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