aliehsaeedii commented on code in PR #18652: URL: https://github.com/apache/kafka/pull/18652#discussion_r1930362996
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java: ########## @@ -0,0 +1,401 @@ +/* + * 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.streams.assignor; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.Comparator; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Iterator; +import java.util.Map; +import java.util.Objects; +import java.util.Optional; +import java.util.Set; +import java.util.stream.Collectors; + +public class StickyTaskAssignor implements TaskAssignor { + + public static final String STICKY_ASSIGNOR_NAME = "sticky"; + private static final Logger log = LoggerFactory.getLogger(StickyTaskAssignor.class); + // helper data structures: + private TaskPairs taskPairs; + Map<TaskId, Member> activeTaskToPrevMember; + Map<TaskId, Set<Member>> standbyTaskToPrevMember; + Map<String, ProcessState> processIdToState; + int allTasks; + int totalCapacity; + int tasksPerMember; + + @Override + public String name() { + return STICKY_ASSIGNOR_NAME; + } + + @Override + public GroupAssignment assign(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber) throws TaskAssignorException { + initialize(groupSpec, topologyDescriber); + //active + Set<TaskId> activeTasks = toTaskIds(groupSpec, topologyDescriber, true); + assignActive(activeTasks); + //standby + final int numStandbyReplicas = + groupSpec.assignmentConfigs().isEmpty() ? 0 + : Integer.parseInt(groupSpec.assignmentConfigs().get("numStandbyReplicas")); + if (numStandbyReplicas > 0) { + Set<TaskId> statefulTasks = toTaskIds(groupSpec, topologyDescriber, false); + assignStandby(statefulTasks, numStandbyReplicas); + } + return buildGroupAssignment(groupSpec.members().keySet()); + } + + private Set<TaskId> toTaskIds(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber, final boolean isActive) { + Set<TaskId> ret = new HashSet<>(); + for (String subtopology : groupSpec.subtopologies()) { + if (isActive || topologyDescriber.isStateful(subtopology)) { + int numberOfPartitions = topologyDescriber.numTasks(subtopology); + for (int i = 0; i < numberOfPartitions; i++) { + ret.add(new TaskId(subtopology, i)); + } + } + } + return ret; + } + + private void initialize(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber) { + allTasks = 0; + for (String subtopology : groupSpec.subtopologies()) { + int numberOfPartitions = topologyDescriber.numTasks(subtopology); + allTasks += numberOfPartitions; + } + totalCapacity = groupSpec.members().size(); + tasksPerMember = computeTasksPerMember(allTasks, totalCapacity); + taskPairs = new TaskPairs(allTasks * (allTasks - 1) / 2); + processIdToState = new HashMap<>(); + activeTaskToPrevMember = new HashMap<>(); + standbyTaskToPrevMember = new HashMap<>(); + for (Map.Entry<String, AssignmentMemberSpec> memberEntry : groupSpec.members().entrySet()) { + final String memberId = memberEntry.getKey(); + final String processId = memberEntry.getValue().processId(); + final Member member = new Member(processId, memberId); + final AssignmentMemberSpec memberSpec = memberEntry.getValue(); + processIdToState.putIfAbsent(processId, new ProcessState(processId)); + processIdToState.get(processId).addMember(memberId); + // prev active tasks + for (Map.Entry<String, Set<Integer>> entry : memberSpec.activeTasks().entrySet()) { Review Comment: What do you mean by handling @bbejeck? We need the following things for assignment computation: 1. all tasks: we retrieve it from `GroupSpec` and `TopologyDescriber` 2. prev tasks (to re-assign the same tasks to them for more efficiency, specifically with stateful tasks): from the existing members. If a member is out of the group, we cannot re-assign tasks to it and have to re-assign its tasks to other available members. 3. current available members: which is also retrieved from `GroupSpec` ([here](https://github.com/aliehsaeedii/kafka/blob/3fdad5196a5137c1ed6cd8c1bd26454a569838fb/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java#L100-L110)) Is there any point I'm missing? If yes, I've missed a very important thing. Which integration test is currently covering this? I assume I've implemented the current behaviour, but thanks for double-checking. I think we are lacking some integration tests here. -- This is an automated message from the Apache Git Service. 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