lkokhreidze commented on a change in pull request #10851: URL: https://github.com/apache/kafka/pull/10851#discussion_r671829899
########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientTagAwareStandbyTaskAssignor.java ########## @@ -0,0 +1,212 @@ +/* + * 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.Optional; +import java.util.Set; +import java.util.TreeMap; +import java.util.UUID; +import java.util.function.Function; + +import static java.util.stream.Collectors.toMap; + +/** + * Distributes standby tasks over different tag dimensions. + * Only tags specified via {@link AssignmentConfigs#rackAwareAssignmentTags} are taken into account. + * Standby task distribution is on a best-effort basis. For example, if there are not enough clients available + * on different tag dimensions compared to an active and corresponding standby task, + * in that case, the algorithm will fall back to distributing tasks on least-loaded clients. + */ +class ClientTagAwareStandbyTaskAssignor extends StandbyTaskAssignor { + private static final Logger log = LoggerFactory.getLogger(ClientTagAwareStandbyTaskAssignor.class); + + ClientTagAwareStandbyTaskAssignor(final AssignmentConfigs configs) { + super(configs); + } + + @Override + public void assignStandbyTasks(final Map<TaskId, UUID> statefulTasksWithClients, + final TreeMap<UUID, ClientState> clientStates) { + final int numStandbyReplicas = configs.numStandbyReplicas; + final Set<String> rackAwareAssignmentTags = new HashSet<>(configs.rackAwareAssignmentTags); + + final StandbyTaskDistributor standbyTaskDistributor = new StandbyTaskDistributor( + numStandbyReplicas, + clientStates, + rackAwareAssignmentTags, + statefulTasksWithClients + ); + + statefulTasksWithClients.forEach(standbyTaskDistributor::assignStandbyTasksForActiveTask); + } + + @Override + public boolean isValidTaskMovement(final TaskMovementAttempt taskMovementAttempt) { + final Map<String, String> sourceClientTags = taskMovementAttempt.sourceClient().clientTags(); + final Map<String, String> destinationClientTags = taskMovementAttempt.destinationClient().clientTags(); + + for (final Entry<String, String> sourceClientTagEntry : sourceClientTags.entrySet()) { + if (!sourceClientTagEntry.getValue().equals(destinationClientTags.get(sourceClientTagEntry.getKey()))) { + return false; + } + } + + return true; + } + + private static final class StandbyTaskDistributor { Review comment: That is correct. Currently, `StandbyTaskAssignor` implementations are created once per `TaskAssignor#assign` method call, and `assignStandbyTasks` is called only once. I just didn't want to assume how and how many times `assignStandbyTasks` is called as I didn't want to leak the implementation details to the caller. However, if you feel strongly that it's better to have the implementation in the `ClientTagAwareStandbyTaskAssignor`, I can refactor the code. Since it's internal contract of the assignment, maybe it's okay. -- 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
