From: Kai Moritz <kai@juplo.de>
Date: Tue, 5 Apr 2022 20:25:47 +0000 (+0200)
Subject: Rebalance-Listener anstatt Wegwerfen der Map
X-Git-Tag: offset-endpoint~9
X-Git-Url: http://juplo.de/gitweb/?a=commitdiff_plain;h=ae2e7a02860a3ac4b26073bf0bf000a84fe894b9;p=demos%2Fkafka%2Ftraining

Rebalance-Listener anstatt Wegwerfen der Map
---

diff --git a/src/main/java/de/juplo/kafka/EndlessConsumer.java b/src/main/java/de/juplo/kafka/EndlessConsumer.java
index 357a0b4..9aa8152 100644
--- a/src/main/java/de/juplo/kafka/EndlessConsumer.java
+++ b/src/main/java/de/juplo/kafka/EndlessConsumer.java
@@ -1,18 +1,17 @@
 package de.juplo.kafka;
 
 import lombok.extern.slf4j.Slf4j;
+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.consumer.KafkaConsumer;
+import org.apache.kafka.common.TopicPartition;
 import org.apache.kafka.common.errors.WakeupException;
 import org.apache.kafka.common.serialization.StringDeserializer;
 
 import javax.annotation.PreDestroy;
 import java.time.Duration;
-import java.util.Arrays;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Properties;
+import java.util.*;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
@@ -34,7 +33,7 @@ public class EndlessConsumer implements Runnable
   private KafkaConsumer<String, String> consumer = null;
   private Future<?> future = null;
 
-  private Map<Integer, Map<String, Integer>> seen;
+  private final Map<Integer, Map<String, Integer>> seen = new HashMap<>();
 
 
   public EndlessConsumer(
@@ -70,9 +69,20 @@ public class EndlessConsumer implements Runnable
       this.consumer = new KafkaConsumer<>(props);
 
       log.info("{} - Subscribing to topic {}", id, topic);
-      consumer.subscribe(Arrays.asList(topic));
+      consumer.subscribe(Arrays.asList(topic), new ConsumerRebalanceListener()
+      {
+        @Override
+        public void onPartitionsRevoked(Collection<TopicPartition> partitions)
+        {
+          partitions.forEach(tp -> seen.remove(tp.partition()));
+        }
 
-      seen = new HashMap<>();
+        @Override
+        public void onPartitionsAssigned(Collection<TopicPartition> partitions)
+        {
+          partitions.forEach(tp -> seen.put(tp.partition(), new HashMap<>()));
+        }
+      });
 
       while (true)
       {
@@ -96,10 +106,6 @@ public class EndlessConsumer implements Runnable
 
           Integer partition = record.partition();
           String key = record.key() == null ? "NULL" : record.key();
-
-          if (!seen.containsKey(partition))
-            seen.put(partition, new HashMap<>());
-
           Map<String, Integer> byKey = seen.get(partition);
 
           if (!byKey.containsKey(key))
@@ -138,7 +144,6 @@ public class EndlessConsumer implements Runnable
               key);
         }
       }
-      seen = null;
 
       log.info("{} - Consumer-Thread exiting", id);
     }