rreddy-22 commented on code in PR #14182: URL: https://github.com/apache/kafka/pull/14182#discussion_r1312619017
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/UniformAssignor.java: ########## @@ -0,0 +1,241 @@ +/* + * 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.assignor; + +import org.apache.kafka.coordinator.group.common.TopicIdPartition; +import org.apache.kafka.common.Uuid; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.Comparator; +import java.util.HashMap; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.Set; +import java.util.stream.Collectors; +import java.util.stream.IntStream; + +/** + * The Uniform Assignor distributes Kafka topic partitions among group members for balanced assignment. + * The assignor employs two different strategies based on the nature of topic + * subscriptions across the group members: + * <ul> + * <li> + * <b> Optimized Uniform Assignment Builder: </b> This strategy is used when all members have subscribed + * to the same set of topics. + * </li> + * <li> + * <b> General Uniform Assignment Builder: </b> This strategy is used when members have varied topic + * subscriptions. + * </li> + * </ul> + * + * The appropriate strategy is automatically chosen based on the current members' topic subscriptions. + * + * @see OptimizedUniformAssignmentBuilder + * @see GeneralUniformAssignmentBuilder + */ +public class UniformAssignor implements PartitionAssignor { + private static final Logger log = LoggerFactory.getLogger(UniformAssignor.class); + public static final String UNIFORM_ASSIGNOR_NAME = "uniform"; + + @Override + public String name() { + return UNIFORM_ASSIGNOR_NAME; + } + + /** + * Perform the group assignment given the current members and + * topic metadata. + * + * @param assignmentSpec The member assignment spec. + * @param subscribedTopicDescriber The topic and cluster metadata describer {@link SubscribedTopicDescriber}. + * @return The new assignment for the group. + */ + @Override + public GroupAssignment assign( + AssignmentSpec assignmentSpec, + SubscribedTopicDescriber subscribedTopicDescriber + ) throws PartitionAssignorException { + + AbstractAssignmentBuilder assignmentBuilder; + if (allSubscriptionsEqual(assignmentSpec.members())) { + log.debug("Detected that all members are subscribed to the same set of topics, invoking the " + + "optimized assignment algorithm"); + assignmentBuilder = new OptimizedUniformAssignmentBuilder(assignmentSpec, subscribedTopicDescriber); + } else { + assignmentBuilder = new GeneralUniformAssignmentBuilder(); + log.debug("Detected that all members are subscribed to a different set of topics, invoking the " + + "general assignment algorithm"); + } + return assignmentBuilder.buildAssignment(); + } + + /** + * Determines if all members are subscribed to the same list of topic IDs. + * + * @param members A map of member identifiers to their respective {@code AssignmentMemberSpec}. + * Assumes the map is non-empty. + * @return true if all members have the same subscription list of topic IDs, + * false otherwise. + */ + private boolean allSubscriptionsEqual(Map<String, AssignmentMemberSpec> members) { + boolean allSubscriptionsEqual = true; + Collection<Uuid> firstSubscriptionList = members.values().iterator().next().subscribedTopicIds(); + for (AssignmentMemberSpec memberSpec : members.values()) { + if (!firstSubscriptionList.equals(memberSpec.subscribedTopicIds())) { + allSubscriptionsEqual = false; + break; + } + } + return allSubscriptionsEqual; + } + + protected static abstract class AbstractAssignmentBuilder { + protected abstract GroupAssignment buildAssignment(); + + protected boolean useRackAwareAssignment( + Set<String> consumerRacks, + Set<String> partitionRacks, + Map<TopicIdPartition, Set<String>> racksPerPartition + ) { + if (consumerRacks.isEmpty() || Collections.disjoint(consumerRacks, partitionRacks)) + return false; + else { + return !racksPerPartition.values().stream().allMatch(partitionRacks::equals); + } + } + + protected List<TopicIdPartition> getAllTopicIdPartitions( + List<Uuid> listAllTopics, + SubscribedTopicDescriber subscribedTopicDescriber + ) { + List<TopicIdPartition> allTopicIdPartitions = new ArrayList<>(); + listAllTopics.forEach(topic -> + IntStream.range(0, subscribedTopicDescriber.numPartitions((topic))) + .forEach(i -> allTopicIdPartitions.add(new TopicIdPartition(topic, i)) + ) + ); + + return allTopicIdPartitions; + } + + protected class RackInfo { + protected final Map<String, String> memberRacks; + protected final Map<TopicIdPartition, Set<String>> partitionRacks; + private final Map<TopicIdPartition, Integer> numMembersByPartition; + + public RackInfo( + AssignmentSpec assignmentSpec, + SubscribedTopicDescriber subscribedTopicDescriber, + List<Uuid> topicIds + ) { + Map<String, List<String>> membersByRack = new HashMap<>(); + assignmentSpec.members().forEach((memberId, assignmentMemberSpec) -> + assignmentMemberSpec.rackId().filter(r -> !r.isEmpty()).ifPresent( + rackId -> membersByRack.computeIfAbsent(rackId, k -> new ArrayList<>()).add(memberId) + ) + ); + + Set<String> allPartitionRacks; + Map<TopicIdPartition, Set<String>> partitionRacks; + List<TopicIdPartition> topicIdPartitions = getAllTopicIdPartitions(topicIds, subscribedTopicDescriber); + + if (membersByRack.isEmpty()) { + allPartitionRacks = Collections.emptySet(); + partitionRacks = Collections.emptyMap(); + } else { + partitionRacks = new HashMap<>(); + allPartitionRacks = new HashSet<>(); + topicIdPartitions.forEach(tp -> { + Set<String> racks = subscribedTopicDescriber.racksForPartition(tp.topicId(), tp.partition()); + partitionRacks.put(tp, racks); + if (!racks.isEmpty()) allPartitionRacks.addAll(racks); + }); + } + + if (useRackAwareAssignment(membersByRack.keySet(), allPartitionRacks, partitionRacks)) { + this.memberRacks = new HashMap<>(assignmentSpec.members().size()); + membersByRack.forEach((rack, rackConsumers) -> rackConsumers.forEach(c -> memberRacks.put(c, rack))); + this.partitionRacks = partitionRacks; + } else { + this.memberRacks = Collections.emptyMap(); + this.partitionRacks = Collections.emptyMap(); + } + + numMembersByPartition = partitionRacks.entrySet().stream() + .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().stream() + .map(r -> membersByRack.getOrDefault(r, Collections.emptyList()).size()) + .reduce(0, Integer::sum))); + } + + /** + * Determines if there's a mismatch between the memberId's rack and the partition's replica racks. + * + * <p> Mismatch conditions (returns {@code true}): + * <ul> + * <li> Consumer lacks an associated rack.</li> + * <li> Partition lacks associated replica racks.</li> + * <li> Consumer's rack isn't among the partition's replica racks.</li> + * </ul> + * + * @param memberId The memberId identifier. + * @param tp The topic partition in question. + * @return {@code true} for a mismatch; {@code false} if member and partition racks exist and align. + */ + protected boolean racksMismatch(String memberId, TopicIdPartition tp) { + String consumerRack = memberRacks.get(memberId); + Set<String> replicaRacks = partitionRacks.get(tp); + return consumerRack == null || (replicaRacks == null || !replicaRacks.contains(consumerRack)); + } + + /** + * Sorts the given list of partitions based on the number of consumers available for each partition + * in a rack-aware manner. + * + * @param partitions The list of partitions to be sorted. + * @return A sorted linked list of partitions with potential members in the same rack. + */ + protected List<TopicIdPartition> sortPartitionsByRackConsumers(List<TopicIdPartition> partitions) { Review Comment: numMembersByPartition is a map that's part of the rack info which tracks how many members are in the same rack as the partition. The sum of those members is used to sort them right, that's the "rack aware manner". Sorting happens as expected since I put in print statements to verify them but also without that the assignments wouldn't be as expected and we do a 1:1 check on every assignment in the test cases -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
