fix: Errors during shard-publishing should not kill the instance

[demos/kafka/chat] / src / main / java / de / juplo / kafka / chat / backend / implementation / kafka / InfoChannel.java

diff --git a/src/main/java/de/juplo/kafka/chat/backend/implementation/kafka/InfoChannel.java b/src/main/java/de/juplo/kafka/chat/backend/implementation/kafka/InfoChannel.java
index 3429d40..a6351d0 100644 (file)
--- a/src/main/java/de/juplo/kafka/chat/backend/implementation/kafka/InfoChannel.java
+++ b/src/main/java/de/juplo/kafka/chat/backend/implementation/kafka/InfoChannel.java
@@ -1,10 +1,12 @@
 package de.juplo.kafka.chat.backend.implementation.kafka;
 
 import de.juplo.kafka.chat.backend.domain.ChatRoomInfo;
+import de.juplo.kafka.chat.backend.domain.exceptions.LoadInProgressException;
 import de.juplo.kafka.chat.backend.implementation.kafka.messages.AbstractMessageTo;
 import de.juplo.kafka.chat.backend.implementation.kafka.messages.info.EventChatRoomCreated;
 import de.juplo.kafka.chat.backend.implementation.kafka.messages.info.EventShardAssigned;
 import de.juplo.kafka.chat.backend.implementation.kafka.messages.info.EventShardRevoked;
+import lombok.Getter;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.kafka.clients.consumer.Consumer;
 import org.apache.kafka.clients.consumer.ConsumerRecord;
@@ -30,6 +32,7 @@ public class InfoChannel implements Runnable
   private final String topic;
   private final Producer<String, AbstractMessageTo> producer;
   private final Consumer<String, AbstractMessageTo> consumer;
+  private final Duration pollingInterval;
   private final int numShards;
   private final String[] shardOwners;
   private final long[] currentOffset;
@@ -38,12 +41,16 @@ public class InfoChannel implements Runnable
   private final String instanceUri;
 
   private boolean running;
+  @Getter
+  private volatile boolean loadInProgress = true;
 
 
   public InfoChannel(
     String topic,
     Producer<String, AbstractMessageTo> producer,
     Consumer<String, AbstractMessageTo> infoChannelConsumer,
+    Duration pollingInterval,
+    int numShards,
     URI instanceUri)
   {
     log.debug(
@@ -54,9 +61,9 @@ public class InfoChannel implements Runnable
     this.producer = producer;
     this.chatRoomInfo = new HashMap<>();
 
-    this.numShards = consumer
-        .partitionsFor(topic)
-        .size();
+    this.pollingInterval = pollingInterval;
+
+    this.numShards = numShards;
     this.shardOwners = new String[numShards];
     this.currentOffset = new long[numShards];
     this.nextOffset = new long[numShards];
@@ -68,13 +75,6 @@ public class InfoChannel implements Runnable
   }
 
 
-  boolean isLoadInProgress()
-  {
-    return IntStream
-        .range(0, numShards)
-        .anyMatch(partition -> nextOffset[partition] < currentOffset[partition]);
-  }
-
   Mono<ChatRoomInfo> sendChatRoomCreatedEvent(
       UUID chatRoomId,
       String name,
@@ -189,14 +189,19 @@ public class InfoChannel implements Runnable
     IntStream
         .range(0, numShards)
         .forEach(partition -> this.nextOffset[partition] = 0l);
+    loadInProgress = true;
 
     while (running)
     {
       try
       {
-        ConsumerRecords<String, AbstractMessageTo> records = consumer.poll(Duration.ofMinutes(1));
+        ConsumerRecords<String, AbstractMessageTo> records = consumer.poll(pollingInterval);
         log.debug("Fetched {} messages", records.count());
-        handleMessages(records);
+        for (ConsumerRecord<String, AbstractMessageTo> record : records)
+        {
+          handleMessage(record);
+          updateNextOffset(record.partition(), record.offset() + 1);
+        }
       }
       catch (WakeupException e)
       {
@@ -208,47 +213,52 @@ public class InfoChannel implements Runnable
     log.info("Exiting normally");
   }
 
-  private void handleMessages(ConsumerRecords<String, AbstractMessageTo> records)
+  private void updateNextOffset(int partition, long nextOffset)
   {
-    for (ConsumerRecord<String, AbstractMessageTo> record : records)
-    {
-      switch (record.value().getType())
-      {
-        case EVENT_CHATROOM_CREATED:
-          EventChatRoomCreated eventChatRoomCreated =
-              (EventChatRoomCreated) record.value();
-          createChatRoom(eventChatRoomCreated.toChatRoomInfo());
-          break;
-
-        case EVENT_SHARD_ASSIGNED:
-          EventShardAssigned eventShardAssigned =
-              (EventShardAssigned) record.value();
-          log.info(
-              "Shard {} was assigned to {}",
-              eventShardAssigned.getShard(),
-              eventShardAssigned.getUri());
-          shardOwners[eventShardAssigned.getShard()] = eventShardAssigned.getUri();
-          break;
-
-        case EVENT_SHARD_REVOKED:
-          EventShardRevoked eventShardRevoked =
-              (EventShardRevoked) record.value();
-          log.info(
-              "Shard {} was revoked from {}",
-              eventShardRevoked.getShard(),
-              eventShardRevoked.getUri());
-          shardOwners[eventShardRevoked.getShard()] = null;
-          break;
-
-        default:
-          log.debug(
-              "Ignoring message for key={} with offset={}: {}",
-              record.key(),
-              record.offset(),
-              record.value());
-      }
+    this.nextOffset[partition] = nextOffset;
+    if (loadInProgress) {
+      loadInProgress = IntStream
+          .range(0, numShards)
+          .anyMatch(shard -> this.nextOffset[shard] < currentOffset[partition]);
+    }
+  }
 
-      nextOffset[record.partition()] = record.offset() + 1;
+  private void handleMessage(ConsumerRecord<String, AbstractMessageTo> record)
+  {
+    switch (record.value().getType())
+    {
+      case EVENT_CHATROOM_CREATED:
+        EventChatRoomCreated eventChatRoomCreated =
+            (EventChatRoomCreated) record.value();
+        createChatRoom(eventChatRoomCreated.toChatRoomInfo());
+        break;
+
+      case EVENT_SHARD_ASSIGNED:
+        EventShardAssigned eventShardAssigned =
+            (EventShardAssigned) record.value();
+        log.info(
+            "Shard {} was assigned to {}",
+            eventShardAssigned.getShard(),
+            eventShardAssigned.getUri());
+        shardOwners[eventShardAssigned.getShard()] = eventShardAssigned.getUri();
+        break;
+
+      case EVENT_SHARD_REVOKED:
+        EventShardRevoked eventShardRevoked =
+            (EventShardRevoked) record.value();
+        log.info(
+            "Shard {} was revoked from {}",
+            eventShardRevoked.getShard(),
+            eventShardRevoked.getUri());
+        shardOwners[eventShardRevoked.getShard()] = null;
+        break;
+
+      default:
+        log.debug(
+            "Ignoring message for key={} with offset={}: {}",
+            record.key(),
+            record.offset(),
+            record.value());
     }
   }
 
@@ -282,6 +292,11 @@ public class InfoChannel implements Runnable
 
   Mono<ChatRoomInfo> getChatRoomInfo(UUID id)
   {
+    if (loadInProgress)
+    {
+      return Mono.error(new LoadInProgressException());
+    }
+
     return Mono.fromSupplier(() -> chatRoomInfo.get(id));
   }