lkokhreidze commented on a change in pull request #10851: URL: https://github.com/apache/kafka/pull/10851#discussion_r810003432
########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientTagAwareStandbyTaskAssignor.java ########## @@ -0,0 +1,295 @@ +/* + * 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.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Map.Entry; +import java.util.Objects; +import java.util.Set; +import java.util.UUID; + +import static org.apache.kafka.streams.processor.internals.assignment.StandbyTaskAssignmentUtils.computeTasksToRemainingStandbys; +import static org.apache.kafka.streams.processor.internals.assignment.StandbyTaskAssignmentUtils.pollClientAndMaybeAssignRemainingStandbyTasks; + +/** + * Distributes standby tasks over different tag dimensions. Standby task distribution is on a best-effort basis. + * If rack aware standby task assignment is not possible, implementation fall backs to distributing standby tasks on least-loaded clients. + * + * @see DefaultStandbyTaskAssignor + */ +class ClientTagAwareStandbyTaskAssignor implements StandbyTaskAssignor { + private static final Logger log = LoggerFactory.getLogger(ClientTagAwareStandbyTaskAssignor.class); + + /** + * The algorithm distributes standby tasks for the {@param statefulTaskIds} over different tag dimensions. + * For each stateful task, the number of standby tasks will be assigned based on configured {@link AssignmentConfigs#numStandbyReplicas}. + * Rack aware standby tasks distribution only takes into account tags specified via {@link AssignmentConfigs#rackAwareAssignmentTags}. + * Ideally, all standby tasks for any given stateful task will be located on different tag dimensions to have the best possible distribution. + * However, if the ideal distribution is impossible, the algorithm will fall back to the least-loaded clients without considering rack awareness constraints into consideration. + * The least-loaded clients are determined based on the total number of tasks (active and standby tasks) assigned to the client. + */ + @Override + public boolean assign(final Map<UUID, ClientState> clients, + final Set<TaskId> allTaskIds, + final Set<TaskId> statefulTaskIds, + final AssignorConfiguration.AssignmentConfigs configs) { + final int numStandbyReplicas = configs.numStandbyReplicas; + final Set<String> rackAwareAssignmentTags = new HashSet<>(configs.rackAwareAssignmentTags); + + final Map<TaskId, Integer> tasksToRemainingStandbys = computeTasksToRemainingStandbys( + numStandbyReplicas, + allTaskIds + ); + + final Map<String, Set<String>> tagKeyToValues = new HashMap<>(); Review comment: Can do, but also `Set` makes it easier to handle duplicate values as we are looking for distinct count values here. Not sure if refactoring is worth it though. -- 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
