juplo.de Git - demos/kafka/chat/blob - src/main/java/de/juplo/kafka/chat/backend/persistence/kafka/KafkaChatHomeService.java

   1 package de.juplo.kafka.chat.backend.persistence.kafka;
   2
   3 import de.juplo.kafka.chat.backend.domain.ChatHomeService;
   4 import de.juplo.kafka.chat.backend.domain.ChatRoom;
   5 import de.juplo.kafka.chat.backend.domain.Message;
   6 import de.juplo.kafka.chat.backend.domain.ShardNotOwnedException;
   7 import de.juplo.kafka.chat.backend.persistence.KafkaLikeShardingStrategy;
   8 import lombok.extern.slf4j.Slf4j;
   9 import org.apache.kafka.clients.consumer.Consumer;
  10 import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
  11 import org.apache.kafka.clients.consumer.ConsumerRecord;
  12 import org.apache.kafka.clients.consumer.ConsumerRecords;
  13 import org.apache.kafka.clients.producer.Producer;
  14 import org.apache.kafka.clients.producer.ProducerRecord;
  15 import org.apache.kafka.common.TopicPartition;
  16 import reactor.core.publisher.Flux;
  17 import reactor.core.publisher.Mono;
  18
  19 import java.time.*;
  20 import java.util.*;
  21 import java.util.concurrent.ExecutorService;
  22
  23
  24 @Slf4j
  25 public class KafkaChatHomeService implements ChatHomeService, Runnable, ConsumerRebalanceListener
  26 {
  27   private final ExecutorService executorService;
  28   private final Consumer<String, MessageTo> consumer;
  29   private final Producer<String, MessageTo> producer;
  30   private final String topic;
  31   private final ZoneId zoneId;
  32   private final int numShards;
  33   private final boolean[] isShardOwned;
  34   private final long[] currentOffset;
  35   private final long[] nextOffset;
  36   private final Map<UUID, ChatRoom>[] chatRoomMaps;
  37   private final KafkaLikeShardingStrategy shardingStrategy;
  38
  39   private boolean running;
  40   private volatile boolean loadInProgress;
  41
  42
  43   public KafkaChatHomeService(
  44     ExecutorService executorService,
  45     Consumer<String, MessageTo> consumer,
  46     Producer<String, MessageTo> producer,
  47     String topic,
  48     ZoneId zoneId,
  49     int numShards)
  50   {
  51     log.debug("Creating KafkaChatHomeService");
  52     this.executorService = executorService;
  53     this.consumer = consumer;
  54     this.producer = producer;
  55     this.topic = topic;
  56     this.zoneId = zoneId;
  57     this.numShards = numShards;
  58     this.isShardOwned = new boolean[numShards];
  59     this.currentOffset = new long[numShards];
  60     this.nextOffset = new long[numShards];
  61     this.chatRoomMaps = new Map[numShards];
  62     this.shardingStrategy = new KafkaLikeShardingStrategy(numShards);
  63   }
  64
  65
  66   @Override
  67   public void onPartitionsAssigned(Collection<TopicPartition> partitions)
  68   {
  69     loadInProgress = true;
  70
  71     consumer.endOffsets(partitions).forEach((topicPartition, currentOffset) ->
  72     {
  73       int partition = topicPartition.partition();
  74       isShardOwned[partition] =  true;
  75       this.currentOffset[partition] = currentOffset;
  76
  77       log.info(
  78           "Partition assigned: {} - loading messages: next={} -> current={}",
  79           partition,
  80           nextOffset[partition],
  81           currentOffset);
  82
  83       consumer.seek(topicPartition, nextOffset[partition]);
  84     });
  85
  86     consumer.resume(partitions);
  87   }
  88
  89   @Override
  90   public void onPartitionsRevoked(Collection<TopicPartition> partitions)
  91   {
  92     partitions.forEach(topicPartition ->
  93     {
  94       int partition = topicPartition.partition();
  95       isShardOwned[partition] = false;
  96       log.info("Partition revoked: {} - next={}", partition, nextOffset[partition]);
  97     });
  98   }
  99
 100   @Override
 101   public void onPartitionsLost(Collection<TopicPartition> partitions)
 102   {
 103     log.warn("Lost partitions: {}, partitions");
 104     // TODO: Muss auf den Verlust anders reagiert werden?
 105     onPartitionsRevoked(partitions);
 106   }
 107
 108   @Override
 109   public void run()
 110   {
 111     consumer.subscribe(List.of(topic));
 112
 113     running = true;
 114
 115     try
 116     {
 117       while (running)
 118       {
 119         ConsumerRecords<String, MessageTo> records = consumer.poll(Duration.ofMinutes(5));
 120         log.info("Fetched {} messages", records.count());
 121
 122         if (loadInProgress)
 123         {
 124           for (ConsumerRecord<String, MessageTo> record : records)
 125           {
 126             UUID chatRoomId = UUID.fromString(record.key());
 127             MessageTo messageTo = record.value();
 128
 129             Message.MessageKey key = Message.MessageKey.of(messageTo.getUser(), messageTo.getId());
 130
 131             Instant instant = Instant.ofEpochSecond(record.timestamp());
 132             LocalDateTime timestamp = LocalDateTime.ofInstant(instant, zoneId);
 133
 134             Message message = new Message(key, record.offset(), timestamp, messageTo.getText());
 135
 136             ChatRoom chatRoom = chatRoomMaps[record.partition()].get(chatRoomId);
 137             KafkaChatRoomService kafkaChatRoomService =
 138                 (KafkaChatRoomService) chatRoom.getChatRoomService();
 139
 140             kafkaChatRoomService.persistMessage(message);
 141           }
 142         }
 143         else
 144         {
 145           if (!records.isEmpty())
 146           {
 147             throw new IllegalStateException("All owned partitions should be paused, when no load is in progress!");
 148           }
 149         }
 150       }
 151     }
 152   }
 153
 154   Mono<Message> sendMessage(
 155       UUID chatRoomId,
 156       Message.MessageKey key,
 157       LocalDateTime timestamp,
 158       String text)
 159   {
 160     int shard = this.shardingStrategy.selectShard(chatRoomId);
 161     TopicPartition tp = new TopicPartition(topic, shard);
 162     ZonedDateTime zdt = ZonedDateTime.of(timestamp, zoneId);
 163     return Mono.create(sink ->
 164     {
 165       ProducerRecord<String, MessageTo> record =
 166           new ProducerRecord<>(
 167               tp.topic(),
 168               tp.partition(),
 169               zdt.toEpochSecond(),
 170               chatRoomId.toString(),
 171               MessageTo.of(key.getUsername(), key.getMessageId(), text));
 172
 173       producer.send(record, ((metadata, exception) ->
 174       {
 175         if (metadata != null)
 176         {
 177           // On successful send
 178           Message message = new Message(key, metadata.offset(), timestamp, text);
 179           log.info("Successfully send message {}", message);
 180           sink.success(message);
 181         }
 182         else
 183         {
 184           // On send-failure
 185           log.error(
 186               "Could not send message for chat-room={}, key={}, timestamp={}, text={}: {}",
 187               chatRoomId,
 188               key,
 189               timestamp,
 190               text,
 191               exception);
 192           sink.error(exception);
 193         }
 194       }));
 195     });
 196   }
 197
 198
 199   @Override
 200   public Mono<ChatRoom> getChatRoom(int shard, UUID id)
 201   {
 202     if (loadInProgress)
 203     {
 204       throw new ShardNotOwnedException(shard);
 205     }
 206     else
 207     {
 208       return Mono.justOrEmpty(chatRoomMaps[shard].get(id));
 209     }
 210   }
 211
 212   @Override
 213   public Flux<ChatRoom> getChatRooms(int shard)
 214   {
 215     if (loadInProgress)
 216     {
 217       throw new ShardNotOwnedException(shard);
 218     }
 219     else
 220     {
 221       return Flux.fromStream(chatRoomMaps[shard].values().stream());
 222     }
 223   }
 224 }