Implementierung des Consumers aus 'first-contact' vereinfacht

* Code für ordentliches Herunterfahren so weit wie möglich vereinfacht.
* Dabei den Code möglichst eng an die Producer-Implementierung angelehnt.

diff --git a/pom.xml b/pom.xml
index 70f37e8..2b39e97 100644 (file)
--- a/pom.xml
+++ b/pom.xml
@@ -12,8 +12,8 @@
   </parent>
 
   <groupId>de.juplo.kafka</groupId>
-  <artifactId>first-contact</artifactId>
-  <name>First Contact: a Simple Producer and a simple Consumer-Group</name>
+  <artifactId>simple-consumer</artifactId>
+  <name>Super Simple Consumer-Group</name>
   <version>1.0-SNAPSHOT</version>
 
   <dependencies>

diff --git a/src/main/java/de/juplo/kafka/SimpleConsumer.java b/src/main/java/de/juplo/kafka/SimpleConsumer.java
index eaa9566..4e2ca8c 100644 (file)
--- a/src/main/java/de/juplo/kafka/SimpleConsumer.java
+++ b/src/main/java/de/juplo/kafka/SimpleConsumer.java
@@ -4,55 +4,49 @@ import lombok.extern.slf4j.Slf4j;
 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.errors.WakeupException;
 import org.apache.kafka.common.serialization.StringDeserializer;
 
 import java.time.Duration;
 import java.util.Arrays;
 import java.util.Properties;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
 
 
 @Slf4j
 public class SimpleConsumer
 {
-  private long consumed = 0;
-  private KafkaConsumer<String, String> consumer;
-  private Lock lock = new ReentrantLock();
-  private Condition stopped = lock.newCondition();
+  private final String id;
+  private final String topic;
+  private final KafkaConsumer<String, String> consumer;
 
+  private long consumed = 0;
+  private volatile boolean running = true;
+  private volatile boolean done = false;
 
-  public SimpleConsumer()
+  public SimpleConsumer(String broker, String topic, String groupId, String clientId)
   {
-    // tag::create[]
     Properties props = new Properties();
-    props.put("bootstrap.servers", ":9092");
-    props.put("group.id", "my-consumer"); // << Used for Offset-Commits
-    // end::create[]
-    props.put("auto.offset.reset", "earliest");
-    // tag::create[]
+    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());
 
-    KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
-    // end::create[]
-    this.consumer = consumer;
+    consumer = new KafkaConsumer<>(props);
+
+    this.topic = topic;
+    this.id = clientId;
   }
 
 
   public void run()
   {
-    String id = "C";
-
     try
     {
       log.info("{} - Subscribing to topic test", id);
       consumer.subscribe(Arrays.asList("test"));
 
       // tag::loop[]
-      while (true)
+      while (running)
       {
         ConsumerRecords<String, String> records =
             consumer.poll(Duration.ofSeconds(1));
@@ -77,55 +71,63 @@ public class SimpleConsumer
       }
       // end::loop[]
     }
-    catch(WakeupException e)
-    {
-      log.info("{} - RIIING!", id);
-    }
     catch(Exception e)
     {
       log.error("{} - Unexpected error: {}", id, e.toString());
     }
     finally
     {
-      this.lock.lock();
-      try
-      {
-        log.info("{} - Closing the KafkaConsumer", id);
-        consumer.close();
-        log.info("{} - DONE!");
-        stopped.signal();
-      }
-      finally
-      {
-        this.lock.unlock();
-        log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
-      }
+      log.info("{} - Closing the KafkaConsumer", id);
+      consumer.close();
+      log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
+      done = true;
     }
   }
 
 
   public static void main(String[] args) throws Exception
   {
-    SimpleConsumer instance = new SimpleConsumer();
+    String broker = ":9092";
+    String topic = "test";
+    String groupId = "my-group";
+    String clientId = "DEV";
+
+    switch (args.length)
+    {
+      case 4:
+        clientId = args[3];
+      case 3:
+        groupId = args[2];
+      case 2:
+        topic = args[1];
+      case 1:
+        broker = args[0];
+    }
+
+
+    SimpleConsumer instance = new SimpleConsumer(broker, topic, groupId, clientId);
 
     Runtime.getRuntime().addShutdownHook(new Thread(() ->
     {
-      instance.lock.lock();
-      try
-      {
-        instance.consumer.wakeup();
-        instance.stopped.await();
-      }
-      catch (InterruptedException e)
-      {
-        log.warn("Interrrupted while waiting for the consumer to stop!", e);
-      }
-      finally
+      instance.running = false;
+      while (!instance.done)
       {
-        instance.lock.unlock();
+        log.info("Waiting for main-thread...");
+        try
+        {
+          Thread.sleep(1000);
+        }
+        catch (InterruptedException e) {}
       }
+      log.info("Shutdown completed.");
     }));
 
+    log.info(
+        "Running SimpleConsumer: broker={}, topic={}, group-id={}, client-id={}",
+        broker,
+        topic,
+        groupId,
+        clientId);
     instance.run();
   }
 }

diff --git a/src/main/java/de/juplo/kafka/SimpleProducer.java b/src/main/java/de/juplo/kafka/SimpleProducer.java
deleted file mode 100644 (file)
index 43a7227..0000000
--- a/src/main/java/de/juplo/kafka/SimpleProducer.java
+++ /dev/null
@@ -1,117 +0,0 @@
-package de.juplo.kafka;
-
-import lombok.extern.slf4j.Slf4j;
-import org.apache.kafka.clients.producer.KafkaProducer;
-import org.apache.kafka.clients.producer.ProducerRecord;
-import org.apache.kafka.common.serialization.StringSerializer;
-
-import java.util.Properties;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Future;
-
-
-@Slf4j
-public class SimpleProducer
-{
-  private final String id;
-  private final String topic;
-  private final KafkaProducer<String, String> producer;
-
-  private long produced = 0;
-
-  public SimpleProducer(String clientId, String topic)
-  {
-    // tag::create[]
-    Properties props = new Properties();
-    props.put("bootstrap.servers", "localhost:9092");
-    props.put("key.serializer", StringSerializer.class.getName());
-    props.put("value.serializer", StringSerializer.class.getName());
-
-    KafkaProducer<String, String> producer = new KafkaProducer<>(props);
-    // end::create[]
-
-    this.id = clientId;
-    this.topic = topic;
-    this.producer = producer;
-  }
-
-  public void run()
-  {
-    long i = 0;
-
-    try
-    {
-      for (; i < 100 ; i++)
-      {
-        send(Long.toString(i%10), Long.toString(i));
-      }
-
-      log.info("{} - Done", id);
-    }
-    finally
-    {
-      log.info("{}: Closing the KafkaProducer", id);
-      producer.close();
-      log.info("{}: Produced {} messages in total, exiting!", id, produced);
-    }
-  }
-
-  void send(String key, String value)
-  {
-    final long time = System.currentTimeMillis();
-
-    final ProducerRecord<String, String> record = new ProducerRecord<>(
-        topic,  // Topic
-        key,    // Key
-        value   // Value
-    );
-
-    producer.send(record, (metadata, e) ->
-    {
-      long now = System.currentTimeMillis();
-      if (e == null)
-      {
-        // HANDLE SUCCESS
-        produced++;
-        log.debug(
-            "{} - Sent key={} message={} partition={}/{} timestamp={} latency={}ms",
-            id,
-            record.key(),
-            record.value(),
-            metadata.partition(),
-            metadata.offset(),
-            metadata.timestamp(),
-            now - time
-        );
-      }
-      else
-      {
-        // HANDLE ERROR
-        log.error(
-            "{} - ERROR key={} timestamp={} latency={}ms: {}",
-            id,
-            record.key(),
-            metadata == null ? -1 : metadata.timestamp(),
-            now - time,
-            e.toString()
-        );
-      }
-    });
-
-    long now = System.currentTimeMillis();
-    log.trace(
-        "{} - Queued #{} key={} latency={}ms",
-        id,
-        value,
-        record.key(),
-        now - time
-    );
-  }
-
-
-  public static void main(String[] args) throws Exception
-  {
-    SimpleProducer producer = new SimpleProducer("P", "test");
-    producer.run();
-  }
-}