refactor: Pushed sharding one layer down in the architecture

[demos/kafka/chat] / src / main / java / de / juplo / kafka / chat / backend / persistence / inmemory / InMemoryChatHomeService.java

diff --git a/src/main/java/de/juplo/kafka/chat/backend/persistence/inmemory/InMemoryChatHomeService.java b/src/main/java/de/juplo/kafka/chat/backend/persistence/inmemory/InMemoryChatHomeService.java
index b2f94ec..25a9bcf 100644 (file)
--- a/src/main/java/de/juplo/kafka/chat/backend/persistence/inmemory/InMemoryChatHomeService.java
+++ b/src/main/java/de/juplo/kafka/chat/backend/persistence/inmemory/InMemoryChatHomeService.java
@@ -1,57 +1,100 @@
-package de.juplo.kafka.chat.backend.persistence;
+package de.juplo.kafka.chat.backend.persistence.inmemory;
 
-import de.juplo.kafka.chat.backend.domain.ChatRoom;
-import de.juplo.kafka.chat.backend.domain.ChatHomeService;
+import de.juplo.kafka.chat.backend.domain.*;
 import lombok.extern.slf4j.Slf4j;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
-import java.time.Clock;
-import java.util.HashMap;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.UUID;
+import java.util.*;
 
 
 @Slf4j
-public class InMemoryChatHomeService implements ChatHomeService<InMemoryChatRoomService>
+public class InMemoryChatHomeService implements ChatHomeService
 {
-  private final Map<UUID, ChatRoom> chatrooms;
-  private final Clock clock;
-  private final int bufferSize;
+  private final Map<UUID, ChatRoom>[] chatrooms;
+  private final Set<Integer> ownedShards;
+  private final ShardingStrategy shardingStrategy;
 
 
   public InMemoryChatHomeService(
-      Flux<ChatRoom> chatroomFlux,
-      Clock clock,
-      int bufferSize)
+      int numShards,
+      int[] ownedShards,
+      ShardingStrategy shardingStrategy,
+      Flux<ChatRoom> chatroomFlux)
   {
-    log.debug("Creating InMemoryChatHomeService with buffer-size {} (for created ChatRoom's)", bufferSize);
-    this.chatrooms = new HashMap<>();
-    chatroomFlux.subscribe(chatroom -> chatrooms.put(chatroom.getId(), chatroom));
-    this.clock = clock;
-    this.bufferSize = bufferSize;
+    log.debug("Creating InMemoryChatHomeService");
+
+    this.chatrooms = new Map[numShards];
+
+    this.ownedShards = Arrays
+        .stream(ownedShards)
+        .collect(
+            () -> new HashSet<>(),
+            (set, i) -> set.add(i),
+            (a, b) -> a.addAll(b));
+
+    this.shardingStrategy = shardingStrategy;
+
+    for (int shard = 0; shard < numShards; shard++)
+    {
+      chatrooms[shard] = this.ownedShards.contains(shard)
+          ? new HashMap<>()
+          : null;
+    }
+    chatroomFlux
+        .filter(chatRoom ->
+        {
+          if (this.ownedShards.contains(chatRoom.getShard()))
+          {
+            return true;
+          }
+          else
+          {
+            log.info("Ignoring not owned chat-room {}", chatRoom);
+            return false;
+          }
+        })
+        .toStream()
+        .forEach(chatroom -> chatrooms[chatroom.getShard()].put(chatroom.getId(), chatroom));
   }
 
-  @Override
-  public Mono<ChatRoom> createChatRoom(UUID id, String name)
+  void putChatRoom(ChatRoom chatRoom)
   {
-    InMemoryChatRoomService service =
-        new InMemoryChatRoomService(new LinkedHashMap<>());
-    ChatRoom chatRoom = new ChatRoom(id, name, clock, service, bufferSize);
-    chatrooms.put(chatRoom.getId(), chatRoom);
-    return Mono.just(chatRoom);
+    UUID id = chatRoom.getId();
+    int shard = shardingStrategy.selectShard(id);
+    if (!ownedShards.contains(shard))
+      throw new ShardNotOwnedException(this, chatRoom, shard, ownedShards);
+    chatrooms[shard].put(id, chatRoom);
   }
 
   @Override
   public Mono<ChatRoom> getChatRoom(UUID id)
   {
-    return Mono.justOrEmpty(chatrooms.get(id));
+    int shard = shardingStrategy.selectShard(id);
+    if (ownedShards.contains(shard))
+    {
+      return Mono.justOrEmpty(chatrooms[shard].get(id));
+    }
+    else
+    {
+      int[] ownedShards = new int[this.ownedShards.size()];
+      Iterator<Integer> iterator = this.ownedShards.iterator();
+      for (int i = 0; iterator.hasNext(); i++)
+      {
+        ownedShards[i] = iterator.next();
+      }
+      return Mono.error(new UnknownChatroomException(
+          id,
+          shard,
+          ownedShards));
+    }
   }
 
   @Override
   public Flux<ChatRoom> getChatRooms()
   {
-    return Flux.fromStream(chatrooms.values().stream());
+    return Flux
+        .fromIterable(ownedShards)
+        .flatMap(shard -> Flux.fromIterable(chatrooms[shard].values()));
   }
 }