コード例 #1
0
            private bool Rebalance(Cluster cluster)
            {
                var myTopicThreadIdsMap =
                    TopicCount.ConstructTopicCount(group, consumerIdString, parent.zkClient)
                    .GetConsumerThreadIdsPerTopic();
                var consumersPerTopicMap = ZkUtils.GetConsumersPerTopic(parent.zkClient, group);
                var brokers = ZkUtils.GetAllBrokersInCluster(parent.zkClient);

                if (brokers.Count == 0)
                {
                    // This can happen in a rare case when there are no brokers available in the cluster when the consumer is started.
                    // We log an warning and register for child changes on brokers/id so that rebalance can be triggered when the brokers
                    // are up.
                    Logger.Warn("no brokers found when trying to rebalance.");
                    parent.zkClient.SubscribeChildChanges(ZkUtils.BrokerIdsPath, parent.loadBalancerListener);
                    return(true);
                }
                else
                {
                    var partitionsAssignmentPerTopicMap = ZkUtils.GetPartitionAssignmentForTopics(
                        parent.zkClient, myTopicThreadIdsMap.Keys.ToList());
                    var partitionsPerTopicMap = partitionsAssignmentPerTopicMap.ToDictionary(
                        p => p.Key, p => p.Value.Keys.OrderBy(x => x).ToList());

                    /**
                     * fetchers must be stopped to avoid Data duplication, since if the current
                     * rebalancing attempt fails, the partitions that are released could be owned by another consumer.
                     * But if we don't stop the fetchers first, this consumer would continue returning Data for released
                     * partitions in parallel. So, not stopping the fetchers leads to duplicate Data.
                     */

                    this.CloseFetchers(cluster, (IDictionary <string, IList <KafkaStream <TKey, TValue> > >)KafkaMessageAndMetadataStreams, myTopicThreadIdsMap);

                    this.ReleasePartitionOwnership(parent.topicRegistry);

                    var partitionOwnershipDecision = new Dictionary <Tuple <string, int>, string>();
                    var currentTopicRegistry       = new Pool <string, Pool <int, PartitionTopicInfo> >();

                    foreach (var topicAndConsumerThreadIsSet in myTopicThreadIdsMap)
                    {
                        var topic = topicAndConsumerThreadIsSet.Key;
                        var consumerThreadIdSet = topicAndConsumerThreadIsSet.Value;

                        currentTopicRegistry[topic] = new Pool <int, PartitionTopicInfo>();

                        var topicDirs     = new ZKGroupTopicDirs(group, topic);
                        var curConsumers  = consumersPerTopicMap.Get(topic);
                        var curPartitions = partitionsPerTopicMap.Get(topic);

                        var nPartsPerConsumer       = curPartitions.Count / curConsumers.Count;
                        var nConsumersWithExtraPart = curPartitions.Count % curConsumers.Count;

                        Logger.InfoFormat("Consumer {0} rebalancing the following partitions: {1} for topic {2} with consumers: {3}", consumerIdString, string.Join(",", curPartitions), topic, string.Join(",", curConsumers));

                        foreach (var consumerThreadId in consumerThreadIdSet)
                        {
                            var myConsumerPosition = curConsumers.IndexOf(consumerThreadId);
                            Contract.Assert(myConsumerPosition >= 0);
                            var startPart = (nPartsPerConsumer * myConsumerPosition)
                                            + Math.Min(nConsumersWithExtraPart, myConsumerPosition);
                            var nParts = nPartsPerConsumer + (myConsumerPosition + 1 > nConsumersWithExtraPart ? 0 : 1);

                            /**
                             *   Range-partition the sorted partitions to consumers for better locality.
                             *  The first few consumers pick up an extra partition, if any.
                             */

                            if (nParts <= 0)
                            {
                                Logger.WarnFormat(
                                    "No broker partitions consumed by consumer thread {0} for topic {1}",
                                    consumerThreadId,
                                    topic);
                            }
                            else
                            {
                                for (var i = startPart; i < startPart + nParts; i++)
                                {
                                    var partition = curPartitions[i];
                                    Logger.InfoFormat("{0} attempting to claim partition {1}", consumerThreadId, partition);
                                    this.AddPartitionTopicInfo(currentTopicRegistry, topicDirs, partition, topic, consumerThreadId);

                                    // record the partition ownership decision
                                    partitionOwnershipDecision[Tuple.Create(topic, partition)] = consumerThreadId;
                                }
                            }
                        }
                    }

                    /**
                     * move the partition ownership here, since that can be used to indicate a truly successful rebalancing attempt
                     * A rebalancing attempt is completed successfully only after the fetchers have been started correctly
                     */
                    if (this.ReflectPartitionOwnershipDecision(partitionOwnershipDecision))
                    {
                        Logger.Info("Updating the cache");
                        Logger.Debug("Partitions per topic cache " + JObject.FromObject(partitionsPerTopicMap).ToString(Formatting.None));
                        Logger.Debug("Consumers per topic cache " + JObject.FromObject(consumersPerTopicMap).ToString(Formatting.None));
                        parent.topicRegistry = currentTopicRegistry;
                        this.UpdateFetcher(cluster);
                        return(true);
                    }
                    else
                    {
                        return(false);
                    }
                }
            }