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   * 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,
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   * See the License for the specific language governing permissions and
   * limitations under the License.
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  package org.apache.kafka.streams.processor.internals.assignment;
  
  import org.apache.kafka.common.Cluster;
  import org.apache.kafka.common.Node;
  import org.apache.kafka.common.PartitionInfo;
  import org.apache.kafka.common.TopicPartition;
  import org.apache.kafka.common.TopicPartitionInfo;
  import org.apache.kafka.streams.processor.assignment.TaskTopicPartition;
  import org.apache.kafka.streams.processor.internals.InternalTopicManager;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Arrays;
  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;
  
  public final class RackUtils {
  
      private static final Logger LOG = LoggerFactory.getLogger(RackUtils.class);
  
      private RackUtils() { }
  
      public static void annotateTopicPartitionsWithRackInfo(final Cluster cluster,
                                                             final InternalTopicManager internalTopicManager,
                                                             final Set<DefaultTaskTopicPartition> topicPartitions) {
          // First we add all the changelog topics to the set of topics to describe.
          final Set<String> topicsToDescribe = topicPartitions.stream()
              .filter(tp -> !tp.isSource())
              .map(topicPartition -> topicPartition.topicPartition().topic())
              .collect(Collectors.toSet());
  
          // Then we add the non changelog topics that we do not have full information about.
          final Set<TopicPartition> nonChangelogTopics = topicPartitions.stream()
              .filter(taskTopicPartition -> !taskTopicPartition.isChangelog())
              .map(TaskTopicPartition::topicPartition)
              .collect(Collectors.toSet());
          topicsToDescribe.addAll(topicsWithMissingMetadata(cluster, nonChangelogTopics));
  
          // We can issue an RPC call to get up-to-date information about the topics that had rack
          // information missing.
          final Map<String, List<TopicPartitionInfo>> freshTopicPartitionInfo =
              describeTopics(internalTopicManager, topicsToDescribe);
  
          // Finally we compute the list of topics that already have all rack information known.
          final Set<TopicPartition> topicsWithUpToDateMetadata = topicPartitions.stream()
              .map(TaskTopicPartition::topicPartition)
              .filter(topicPartition -> !topicsToDescribe.contains(topicPartition.topic()))
              .collect(Collectors.toSet());
  
          // Lastly we compile the mapping of topic partition to rack ids by combining known data and
          // information that we got from the earlier RPC call.
          final Map<TopicPartition, Set<String>> racksForTopicPartition = knownRacksForPartition(
              cluster, topicsWithUpToDateMetadata);
          freshTopicPartitionInfo.forEach((topic, partitionInfos) -> {
              for (final TopicPartitionInfo partitionInfo : partitionInfos) {
                  final int partition = partitionInfo.partition();
                  final TopicPartition topicPartition = new TopicPartition(topic, partition);
                  final List<Node> replicas = partitionInfo.replicas();
                  if (replicas == null || replicas.isEmpty()) {
                      LOG.error("No replicas found for topic partition {}: {}", topic, partition);
                      continue;
                  }
  
                  final Set<String> racks = replicas.stream().filter(Node::hasRack).map(Node::rack).collect(
                      Collectors.toSet());
                  racksForTopicPartition.computeIfAbsent(topicPartition, k -> new HashSet<>());
                  racksForTopicPartition.get(topicPartition).addAll(racks);
              }
          });
  
          for (final DefaultTaskTopicPartition topicPartition : topicPartitions) {
              if (!racksForTopicPartition.containsKey(topicPartition.topicPartition())) {
                  continue;
              }
  
              final Set<String> racks = racksForTopicPartition.get(topicPartition.topicPartition());
              topicPartition.annotateWithRackIds(racks);
          }
      }
  
      public static Set<String> topicsWithMissingMetadata(final Cluster cluster, final Set<TopicPartition> topicPartitions) {
          final Set<String> topicsWithStaleMetadata = new HashSet<>();
          for (final TopicPartition topicPartition : topicPartitions) {
              final PartitionInfo partitionInfo = cluster.partition(topicPartition);
              if (partitionInfo == null) {
                  LOG.error("TopicPartition {} doesn't exist in cluster", topicPartition);
                  continue;
              }
              final Node[] replica = partitionInfo.replicas();
              if (replica == null || replica.length == 0) {
                  topicsWithStaleMetadata.add(topicPartition.topic());
              }
          }
          return topicsWithStaleMetadata;
      }
  
      public static Map<TopicPartition, Set<String>> knownRacksForPartition(final Cluster cluster, final Set<TopicPartition> topicPartitions) {
          final Map<TopicPartition, Set<String>> racksForPartition = new HashMap<>();
          for (final TopicPartition topicPartition : topicPartitions) {
              final PartitionInfo partitionInfo = cluster.partition(topicPartition);
              if (partitionInfo == null) {
                  LOG.error("TopicPartition {} doesn't exist in cluster", topicPartition);
                  continue;
              }
              final Node[] replicas = partitionInfo.replicas();
              if (replicas == null || replicas.length == 0) {
                  continue;
              }
  
              Arrays.stream(replicas).filter(node -> !node.hasRack()).forEach(node -> {
                  LOG.warn("Node {} for topic partition {} doesn't have rack", node, topicPartition);
              });
              final Set<String> racks = Arrays.stream(replicas).filter(Node::hasRack)
                  .map(Node::rack).collect(Collectors.toSet());
              racksForPartition.put(topicPartition, racks);
          }
          return racksForPartition;
      }
  
      private static Map<String, List<TopicPartitionInfo>> describeTopics(final InternalTopicManager internalTopicManager,
                                                                          final Set<String> topicsToDescribe) {
          if (topicsToDescribe.isEmpty()) {
              return new HashMap<>();
          }
  
          LOG.info("Describing topics for rack information: {}", Arrays.toString(topicsToDescribe.toArray()));
          try {
              final Map<String, List<TopicPartitionInfo>> topicPartitionInfo = internalTopicManager.getTopicPartitionInfo(topicsToDescribe);
              if (topicsToDescribe.size() > topicPartitionInfo.size()) {
                  topicsToDescribe.removeAll(topicPartitionInfo.keySet());
                  LOG.error("Failed to describe topic for {}", topicsToDescribe);
              }
              return topicPartitionInfo;
          } catch (final Exception e) {
              LOG.error("Failed to describe topics {}", topicsToDescribe, e);
              return new HashMap<>();
          }
      }
  }
  