+package de.juplo.kafka.chat.backend.persistence.kafka;
+
+import de.juplo.kafka.chat.backend.domain.ChatRoom;
+import de.juplo.kafka.chat.backend.domain.ChatRoomInfo;
+import de.juplo.kafka.chat.backend.domain.Message;
+import de.juplo.kafka.chat.backend.domain.ShardNotOwnedException;
+import de.juplo.kafka.chat.backend.persistence.kafka.messages.AbstractMessageTo;
+import de.juplo.kafka.chat.backend.persistence.kafka.messages.CommandCreateChatRoomTo;
+import de.juplo.kafka.chat.backend.persistence.kafka.messages.EventChatMessageReceivedTo;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.kafka.clients.consumer.Consumer;
+import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.producer.Producer;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.errors.WakeupException;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.time.*;
+import java.util.*;
+import java.util.stream.IntStream;
+
+
+@Slf4j
+public class ChatRoomChannel implements Runnable, ConsumerRebalanceListener
+{
+ private final String topic;
+ private final Producer<String, AbstractMessageTo> producer;
+ private final Consumer<String, AbstractMessageTo> consumer;
+ private final ZoneId zoneId;
+ private final int numShards;
+ private final int bufferSize;
+ private final Clock clock;
+ private final boolean[] isShardOwned;
+ private final long[] currentOffset;
+ private final long[] nextOffset;
+ private final Map<UUID, ChatRoom>[] chatrooms;
+
+ private boolean running;
+ @Getter
+ private volatile boolean loadInProgress;
+
+
+ public ChatRoomChannel(
+ String topic,
+ Producer<String, AbstractMessageTo> producer,
+ Consumer<String, AbstractMessageTo> consumer,
+ ZoneId zoneId,
+ int numShards,
+ int bufferSize,
+ Clock clock)
+ {
+ log.debug(
+ "Creating ChatRoomChannel for topic {} with {} partitions",
+ topic,
+ numShards);
+ this.topic = topic;
+ this.consumer = consumer;
+ this.producer = producer;
+ this.zoneId = zoneId;
+ this.numShards = numShards;
+ this.bufferSize = bufferSize;
+ this.clock = clock;
+ this.isShardOwned = new boolean[numShards];
+ this.currentOffset = new long[numShards];
+ this.nextOffset = new long[numShards];
+ this.chatrooms = new Map[numShards];
+ IntStream
+ .range(0, numShards)
+ .forEach(shard -> this.chatrooms[shard] = new HashMap<>());
+ }
+
+
+
+ Mono<ChatRoomInfo> sendCreateChatRoomRequest(
+ UUID chatRoomId,
+ String name)
+ {
+ CommandCreateChatRoomTo createChatRoomRequestTo = CommandCreateChatRoomTo.of(name);
+ return Mono.create(sink ->
+ {
+ ProducerRecord<String, AbstractMessageTo> record =
+ new ProducerRecord<>(
+ topic,
+ chatRoomId.toString(),
+ createChatRoomRequestTo);
+
+ producer.send(record, ((metadata, exception) ->
+ {
+ if (metadata != null)
+ {
+ log.info("Successfully send chreate-request for chat room: {}", createChatRoomRequestTo);
+ ChatRoomInfo chatRoomInfo = new ChatRoomInfo(chatRoomId, name, record.partition());
+ createChatRoom(chatRoomInfo);
+ sink.success(chatRoomInfo);
+ }
+ else
+ {
+ // On send-failure
+ log.error(
+ "Could not send create-request for chat room (id={}, name={}): {}",
+ chatRoomId,
+ name,
+ exception);
+ sink.error(exception);
+ }
+ }));
+ });
+ }
+
+ Mono<Message> sendChatMessage(
+ UUID chatRoomId,
+ Message.MessageKey key,
+ LocalDateTime timestamp,
+ String text)
+ {
+ ZonedDateTime zdt = ZonedDateTime.of(timestamp, zoneId);
+ return Mono.create(sink ->
+ {
+ ProducerRecord<String, AbstractMessageTo> record =
+ new ProducerRecord<>(
+ topic,
+ null,
+ zdt.toEpochSecond(),
+ chatRoomId.toString(),
+ EventChatMessageReceivedTo.of(key.getUsername(), key.getMessageId(), text));
+
+ producer.send(record, ((metadata, exception) ->
+ {
+ if (metadata != null)
+ {
+ // On successful send
+ Message message = new Message(key, metadata.offset(), timestamp, text);
+ log.info("Successfully send message {}", message);
+ sink.success(message);
+ }
+ else
+ {
+ // On send-failure
+ log.error(
+ "Could not send message for chat-room={}, key={}, timestamp={}, text={}: {}",
+ chatRoomId,
+ key,
+ timestamp,
+ text,
+ exception);
+ sink.error(exception);
+ }
+ }));
+ });
+ }
+
+ @Override
+ public void onPartitionsAssigned(Collection<TopicPartition> partitions)
+ {
+ log.info("Newly assigned partitions! Pausing normal operations...");
+ loadInProgress = true;
+
+ consumer.endOffsets(partitions).forEach((topicPartition, currentOffset) ->
+ {
+ int partition = topicPartition.partition();
+ isShardOwned[partition] = true;
+ this.currentOffset[partition] = currentOffset;
+
+ log.info(
+ "Partition assigned: {} - loading messages: next={} -> current={}",
+ partition,
+ nextOffset[partition],
+ currentOffset);
+
+ consumer.seek(topicPartition, nextOffset[partition]);
+ });
+
+ consumer.resume(partitions);
+ }
+
+ @Override
+ public void onPartitionsRevoked(Collection<TopicPartition> partitions)
+ {
+ partitions.forEach(topicPartition ->
+ {
+ int partition = topicPartition.partition();
+ isShardOwned[partition] = false;
+ log.info("Partition revoked: {} - next={}", partition, nextOffset[partition]);
+ });
+ }
+
+ @Override
+ public void onPartitionsLost(Collection<TopicPartition> partitions)
+ {
+ log.warn("Lost partitions: {}, partitions");
+ // TODO: Muss auf den Verlust anders reagiert werden?
+ onPartitionsRevoked(partitions);
+ }
+
+ @Override
+ public void run()
+ {
+ running = true;
+
+ while (running)
+ {
+ try
+ {
+ ConsumerRecords<String, AbstractMessageTo> records = consumer.poll(Duration.ofMinutes(5));
+ log.info("Fetched {} messages", records.count());
+
+ if (loadInProgress)
+ {
+ loadChatRoom(records);
+
+ if (isLoadingCompleted())
+ {
+ log.info("Loading of messages completed! Pausing all owned partitions...");
+ pauseAllOwnedPartions();
+ log.info("Resuming normal operations...");
+ loadInProgress = false;
+ }
+ }
+ else
+ {
+ if (!records.isEmpty())
+ {
+ throw new IllegalStateException("All owned partitions should be paused, when no load is in progress!");
+ }
+ }
+ }
+ catch (WakeupException e)
+ {
+ log.info("Received WakeupException, exiting!");
+ running = false;
+ }
+ }
+
+ log.info("Exiting normally");
+ }
+
+ private void loadChatRoom(ConsumerRecords<String, AbstractMessageTo> records)
+ {
+ for (ConsumerRecord<String, AbstractMessageTo> record : records)
+ {
+ UUID chatRoomId = UUID.fromString(record.key());
+
+ switch (record.value().getType())
+ {
+ case COMMAND_CREATE_CHATROOM:
+ createChatRoom(
+ chatRoomId,
+ (CommandCreateChatRoomTo) record.value(),
+ record.partition());
+ break;
+
+ case EVENT_CHATMESSAGE_RECEIVED:
+ Instant instant = Instant.ofEpochSecond(record.timestamp());
+ LocalDateTime timestamp = LocalDateTime.ofInstant(instant, zoneId);
+ loadChatMessage(
+ chatRoomId,
+ timestamp,
+ record.offset(),
+ (EventChatMessageReceivedTo) record.value(),
+ record.partition());
+ break;
+
+ default:
+ log.debug(
+ "Ignoring message for chat-room {} with offset {}: {}",
+ chatRoomId,
+ record.offset(),
+ record.value());
+ }
+
+ nextOffset[record.partition()] = record.offset() + 1;
+ }
+ }
+
+ private void createChatRoom(
+ UUID chatRoomId,
+ CommandCreateChatRoomTo createChatRoomRequestTo,
+ int partition)
+ {
+ log.info("Loading ChatRoom {} with buffer-size {}", chatRoomId, bufferSize);
+ KafkaChatRoomService service = new KafkaChatRoomService(this, chatRoomId);
+ ChatRoom chatRoom = new ChatRoom(
+ chatRoomId,
+ createChatRoomRequestTo.getName(),
+ partition,
+ clock,
+ service,
+ bufferSize);
+ putChatRoom(chatRoom);
+ }
+
+
+ private void createChatRoom(ChatRoomInfo chatRoomInfo)
+ {
+ UUID id = chatRoomInfo.getId();
+ String name = chatRoomInfo.getName();
+ int shard = chatRoomInfo.getShard();
+ log.info("Creating ChatRoom {} with buffer-size {}", id, bufferSize);
+ KafkaChatRoomService service = new KafkaChatRoomService(this, id);
+ ChatRoom chatRoom = new ChatRoom(id, name, shard, clock, service, bufferSize);
+ putChatRoom(chatRoom);
+ }
+
+ private void loadChatMessage(
+ UUID chatRoomId,
+ LocalDateTime timestamp,
+ long offset,
+ EventChatMessageReceivedTo chatMessageTo,
+ int partition)
+ {
+ Message.MessageKey key = Message.MessageKey.of(chatMessageTo.getUser(), chatMessageTo.getId());
+ Message message = new Message(key, offset, timestamp, chatMessageTo.getText());
+
+ ChatRoom chatRoom = chatrooms[partition].get(chatRoomId);
+ KafkaChatRoomService kafkaChatRoomService =
+ (KafkaChatRoomService) chatRoom.getChatRoomService();
+
+ kafkaChatRoomService.persistMessage(message);
+ }
+
+ private boolean isLoadingCompleted()
+ {
+ return IntStream
+ .range(0, numShards)
+ .filter(shard -> isShardOwned[shard])
+ .allMatch(shard -> nextOffset[shard] >= currentOffset[shard]);
+ }
+
+ private void pauseAllOwnedPartions()
+ {
+ consumer.pause(IntStream
+ .range(0, numShards)
+ .filter(shard -> isShardOwned[shard])
+ .mapToObj(shard -> new TopicPartition(topic, shard))
+ .toList());
+ }
+
+
+ private void putChatRoom(ChatRoom chatRoom)
+ {
+ Integer partition = chatRoom.getShard();
+ UUID chatRoomId = chatRoom.getId();
+ if (chatrooms[partition].containsKey(chatRoomId))
+ {
+ log.warn("Ignoring existing chat-room: " + chatRoom);
+ }
+ else
+ {
+ log.info(
+ "Adding new chat-room to partition {}: {}",
+ partition,
+ chatRoom);
+
+ chatrooms[partition].put(chatRoomId, chatRoom);
+ }
+ }
+
+ Mono<ChatRoom> getChatRoom(int shard, UUID id)
+ {
+ if (loadInProgress)
+ {
+ throw new LoadInProgressException(shard);
+ }
+
+ if (!isShardOwned[shard])
+ {
+ throw new ShardNotOwnedException(shard);
+ }
+
+ return Mono.justOrEmpty(chatrooms[shard].get(id));
+ }
+
+ Flux<ChatRoom> getChatRooms()
+ {
+ return Flux
+ .fromStream(IntStream.range(0, numShards).mapToObj(i -> Integer.valueOf(i)))
+ .filter(shard -> isShardOwned[shard])
+ .flatMap(shard -> Flux.fromIterable(chatrooms[shard].values()));
+ }
+}