rreddy-22 commented on code in PR #13638: URL: https://github.com/apache/kafka/pull/13638#discussion_r1179739941
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/consumer/CurrentAssignmentBuilder.java: ########## @@ -0,0 +1,415 @@ +/* + * 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.coordinator.group.consumer; + +import org.apache.kafka.common.Uuid; +import org.apache.kafka.common.message.ConsumerGroupHeartbeatRequestData; + +import java.util.Collections; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.Set; +import java.util.function.BiFunction; + +/** + * The CurrentAssignmentBuilder class encapsulates the reconciliation engine of the + * consumer group protocol. Given the current state of a member and a desired or target + * assignment state, the state machine takes the necessary steps to converge them. + * + * The member state has the following properties: + * - Current Epoch - The current epoch of the member. + * - Next Epoch - The desired epoch of the member. It corresponds to the epoch of + * the target/desired assignment. The member transitions to this epoch + * when it has revoked the partitions that it does not own or if it + * does not have to revoke any. + * - Previous Epoch - The previous epoch of the member when the state was updated. + * - Assigned Set - The set of partitions currently assigned to the member. This represents what + * the member should have. + * - Revoking Set - The set of partitions that the member should revoke before it can transition + * to the next state. + * - Assigning Set - The set of partitions that the member will eventually receive. The partitions + * in this set are still owned by other members in the group. + * + * The state machine has four states: + * - NEW_TARGET_ASSIGNMENT - This is the initial state of the state machine. The state machine starts + * here when the next epoch does not match the target epoch. It means that + * a new target assignment has been installed so the reconciliation process + * must restart. In this state, the Assigned, Revoking and Assigning sets + * are computed. If Revoking is not empty, the state machine transitions + * to REVOKE; if Assigning is not empty, it transitions to ASSIGNING; + * otherwise it transitions to STABLE. + * - REVOKE - This state means that the member must revoke partitions before it can + * transition to the next epoch and thus start receiving new partitions. + * The member transitions to the next state only when it has acknowledged + * the revocation. + * - ASSIGNING - This state means that the member waits on partitions which are still Review Comment: same here, assigning gives the impression that the member is assigning something? -- 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: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
