package de.juplo.kafka;
+import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
+import org.apache.kafka.clients.consumer.Consumer;
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;
+import java.util.concurrent.ExecutorService;
@Slf4j
-public class SimpleConsumer
+@RequiredArgsConstructor
+public class SimpleConsumer implements Runnable
{
- private long consumed = 0;
- private KafkaConsumer<String, String> consumer;
- private Lock lock = new ReentrantLock();
- private Condition stopped = lock.newCondition();
-
-
- public SimpleConsumer()
- {
- // 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("key.deserializer", StringDeserializer.class.getName());
- props.put("value.deserializer", StringDeserializer.class.getName());
+ private final ExecutorService executor;
+ private final String id;
+ private final String topic;
+ private final Consumer<String, Message> consumer;
- KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
- // end::create[]
- this.consumer = consumer;
- }
+ private volatile boolean running = false;
+ private long consumed = 0;
+ @Override
public void run()
{
- String id = "C";
-
try
{
log.info("{} - Subscribing to topic test", id);
consumer.subscribe(Arrays.asList("test"));
+ running = true;
- // tag::loop[]
while (true)
{
- ConsumerRecords<String, String> records =
+ ConsumerRecords<String, Message> records =
consumer.poll(Duration.ofSeconds(1));
- // Do something with the data...
- // end::loop[]
log.info("{} - Received {} messages", id, records.count());
- for (ConsumerRecord<String, String> record : records)
+ for (ConsumerRecord<String, Message> record : records)
{
consumed++;
log.info(
record.value()
);
}
- // tag::loop[]
}
- // end::loop[]
}
catch(WakeupException e)
{
- log.info("{} - RIIING!", id);
+ log.info("{} - Consumer was signaled to finish its work", id);
}
catch(Exception e)
{
- log.error("{} - Unexpected error: {}", id, e.toString());
+ log.error("{} - Unexpected error: {}, unsubscribing!", id, e.toString());
+ consumer.unsubscribe();
}
finally
{
- this.lock.lock();
- try
- {
- log.info("{} - Closing the KafkaConsumer", id);
- consumer.close();
- log.info("C - DONE!");
- stopped.signal();
- }
- finally
- {
- this.lock.unlock();
- log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
- }
+ running = false;
+ log.info("{} - Closing the KafkaConsumer", id);
+ consumer.close();
+ log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
}
}
-
- public static void main(String[] args) throws Exception
+ public void start()
{
- SimpleConsumer instance = new SimpleConsumer();
-
- 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.lock.unlock();
- }
- }));
-
- instance.run();
+ executor.submit(this);
}
}