From: Kai Moritz <kai@juplo.de>
Date: Tue, 11 Mar 2025 17:55:21 +0000 (+0100)
Subject: Vorlage (für das Bauen des Consumers als Docker-Image)
X-Git-Tag: grundlagen/simple-consumer--image--vorlage--2026-06-lvm--rebase-vollständig
X-Git-Url: http://juplo.de/gitweb/?a=commitdiff_plain;h=refs%2Fheads%2Fgrundlagen%2Fsimple-consumer--image--vorlage;p=demos%2Fkafka%2Ftraining

Vorlage (für das Bauen des Consumers als Docker-Image)
---

diff --git a/README.sh b/README.sh
deleted file mode 100755
index 85b8f960..00000000
--- a/README.sh
+++ /dev/null
@@ -1,39 +0,0 @@
-#!/bin/bash
-
-IMAGE=juplo/simple-consumer:1.0-SNAPSHOT
-
-if [ "$1" = "cleanup" ]
-then
-  docker compose -f docker/docker-compose.yml down -t0 -v --remove-orphans
-  mvn clean
-  exit
-fi
-
-docker compose -f docker/docker-compose.yml up -d --remove-orphans kafka-1 kafka-2 kafka-3
-docker compose -f docker/docker-compose.yml rm -svf consumer
-
-if [[
-  $(docker image ls -q $IMAGE) == "" ||
-  "$1" = "build"
-]]
-then
-  mvn clean install || exit
-else
-  echo "Using image existing images:"
-  docker image ls $IMAGE
-fi
-
-docker compose -f docker/docker-compose.yml up --remove-orphans setup || exit 1
-
-
-docker compose -f docker/docker-compose.yml up -d producer
-docker compose -f docker/docker-compose.yml up -d consumer
-
-sleep 5
-docker compose -f docker/docker-compose.yml stop consumer
-
-docker compose -f docker/docker-compose.yml start consumer
-sleep 5
-
-docker compose -f docker/docker-compose.yml stop producer consumer
-docker compose -f docker/docker-compose.yml logs consumer
diff --git a/src/main/java/de/juplo/kafka/ExampleConsumer.java b/src/main/java/de/juplo/kafka/ExampleConsumer.java
index 36ddc70d..f63da160 100644
--- a/src/main/java/de/juplo/kafka/ExampleConsumer.java
+++ b/src/main/java/de/juplo/kafka/ExampleConsumer.java
@@ -1,23 +1,20 @@
 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.Consumer;
 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 java.time.Duration;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Properties;
 
 
 @Slf4j
-public class ExampleConsumer implements ConsumerRebalanceListener
+public class ExampleConsumer
 {
   private final String id;
   private final String topic;
@@ -32,16 +29,16 @@ public class ExampleConsumer implements ConsumerRebalanceListener
     String groupId,
     String clientId)
   {
-    Properties props = new Properties();
-    props.put("bootstrap.servers", broker);
-    props.put("group.id", groupId); // ID für die Offset-Commits
-    props.put("client.id", clientId); // Nur zur Wiedererkennung
-    props.put("key.deserializer", StringDeserializer.class.getName());
-    props.put("value.deserializer", StringDeserializer.class.getName());
+    // TODO:
+    // Instanziierung des KafkaConsumer aus Ihrer bisherigen Implementierung
+    // Hier:
+    // - Den Parameter "broker" des Konstruktors für "bootstrap.servers" verwenden
+    // - Den Parameter "groupId" des Konstruktors für "group.id" verwenden
+    // - Den Parameter "topic" des Konstruktors im Attribut "this.topic" merken
+    // - Den erzeugten KafkaConsumer in "this.consumer" ablegen
 
     this.id = clientId;
     this.topic = topic;
-    consumer = new KafkaConsumer<>(props);
   }
 
 
@@ -50,78 +47,25 @@ public class ExampleConsumer implements ConsumerRebalanceListener
     try
     {
       log.info("{} - Subscribing to topic {}", id, topic);
-      consumer.subscribe(Arrays.asList(topic), this);
+      // TODO: Aufruf von consumer.subscribe()
+      // Hier:
+      // - ACHTUNG: Abonnieren Sie das Topic "this.topic"
       running = true;
 
       while (true)
       {
-        ConsumerRecords<String, String> records = consumer.poll(Duration.ofSeconds(1));
-
-        log.info("{} - Received {} messages", id, records.count());
-        for (ConsumerRecord<String, String> record : records)
-        {
-          handleRecord(
-            record.topic(),
-            record.partition(),
-            record.offset(),
-            record.key(),
-            record.value());
-        }
+        // TODO: Poll & Consume aus Ihrer bisherigen Implementierung
+        // Hier:
+        // - Zählen Sie außerdem die empfangenen Nachrichten in "this.consumed"
       }
     }
-    catch(WakeupException e)
-    {
-      log.info("{} - Consumer was signaled to finish its work", id);
-    }
-    catch(Exception e)
-    {
-      log.error("{} - Unexpected error, unsubscribing!", id, e);
-      consumer.unsubscribe();
-    }
     finally
     {
-      log.info("{} - Closing the KafkaConsumer", id);
-      consumer.close();
       log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
       running = false;
     }
   }
 
-  private void handleRecord(
-    String topic,
-    Integer partition,
-    Long offset,
-    String key,
-    String value)
-  {
-    consumed++;
-    log.info("{} - partition={}-{}, offset={}: {}={}", id, topic, partition, offset, key, value);
-  }
-
-  @Override
-  public void onPartitionsAssigned(Collection<TopicPartition> partitions)
-  {
-    partitions
-      .stream()
-      .forEach(partition -> log.info("{} - partition assigned: {}", id, partition));
-  }
-
-  @Override
-  public void onPartitionsRevoked(Collection<TopicPartition> partitions)
-  {
-    partitions
-      .stream()
-      .forEach(partition -> log.info("{} - partition revoked: {}", id, partition));
-  }
-
-  @Override
-  public void onPartitionsLost(Collection<TopicPartition> partitions)
-  {
-    partitions
-      .stream()
-      .forEach(partition -> log.info("{} - partition lost: {}", id, partition));
-  }
-
 
   public static void main(String[] args) throws Exception
   {
@@ -148,7 +92,7 @@ public class ExampleConsumer implements ConsumerRebalanceListener
 
     Runtime.getRuntime().addShutdownHook(new Thread(() ->
     {
-      instance.consumer.wakeup();
+      // TODO: Endlosschleife beenden
 
       while (instance.running)
       {