juplo.de Git - demos/kafka/training/blob - src/main/java/de/juplo/kafka/EndlessConsumer.java

   1 package de.juplo.kafka;
   2
   3 import lombok.RequiredArgsConstructor;
   4 import lombok.extern.slf4j.Slf4j;
   5 import org.apache.kafka.clients.consumer.*;
   6 import org.apache.kafka.common.TopicPartition;
   7 import org.apache.kafka.common.errors.RecordDeserializationException;
   8 import org.apache.kafka.common.errors.WakeupException;
   9
  10 import javax.annotation.PreDestroy;
  11 import java.time.Duration;
  12 import java.util.*;
  13 import java.util.concurrent.ExecutionException;
  14 import java.util.concurrent.ExecutorService;
  15 import java.util.concurrent.locks.Condition;
  16 import java.util.concurrent.locks.Lock;
  17 import java.util.concurrent.locks.ReentrantLock;
  18
  19
  20 @Slf4j
  21 @RequiredArgsConstructor
  22 public class EndlessConsumer<K, V> implements Runnable
  23 {
  24   private final ExecutorService executor;
  25   private final String id;
  26   private final String topic;
  27   private final Consumer<K, V> consumer;
  28   private final RebalanceListener rebalanceListener;
  29   private final RecordHandler<K, V> recordHandler;
  30
  31   private final Lock lock = new ReentrantLock();
  32   private final Condition condition = lock.newCondition();
  33   private boolean running = false;
  34   private Exception exception;
  35   private long consumed = 0;
  36
  37
  38
  39   @Override
  40   public void run()
  41   {
  42     try
  43     {
  44       log.info("{} - Subscribing to topic {}", id, topic);
  45       consumer.subscribe(Arrays.asList(topic), rebalanceListener);
  46
  47       while (true)
  48       {
  49         ConsumerRecords<K, V> records =
  50             consumer.poll(Duration.ofSeconds(1));
  51
  52         // Do something with the data...
  53         log.info("{} - Received {} messages", id, records.count());
  54         for (ConsumerRecord<K, V> record : records)
  55         {
  56           log.info(
  57               "{} - {}: {}/{} - {}={}",
  58               id,
  59               record.offset(),
  60               record.topic(),
  61               record.partition(),
  62               record.key(),
  63               record.value()
  64           );
  65
  66           recordHandler.accept(record);
  67
  68           consumed++;
  69         }
  70
  71         rebalanceListener.beforeNextPoll();
  72       }
  73     }
  74     catch(WakeupException e)
  75     {
  76       log.info("{} - RIIING! Request to stop consumption - commiting current offsets!", id);
  77       consumer.commitSync();
  78       shutdown();
  79     }
  80     catch(RecordDeserializationException e)
  81     {
  82       TopicPartition tp = e.topicPartition();
  83       long offset = e.offset();
  84       log.error(
  85           "{} - Could not deserialize  message on topic {} with offset={}: {}",
  86           id,
  87           tp,
  88           offset,
  89           e.getCause().toString());
  90
  91       consumer.commitSync();
  92       shutdown(e);
  93     }
  94     catch(Exception e)
  95     {
  96       log.error("{} - Unexpected error: {}", id, e.toString(), e);
  97       shutdown(e);
  98     }
  99     finally
 100     {
 101       log.info("{} - Consumer-Thread exiting", id);
 102     }
 103   }
 104
 105   private void shutdown()
 106   {
 107     shutdown(null);
 108   }
 109
 110   private void shutdown(Exception e)
 111   {
 112     lock.lock();
 113     try
 114     {
 115       try
 116       {
 117         log.info("{} - Unsubscribing from topic {}", id, topic);
 118         consumer.unsubscribe();
 119       }
 120       catch (Exception ue)
 121       {
 122         log.error(
 123             "{} - Error while unsubscribing from topic {}: {}",
 124             id,
 125             topic,
 126             ue.toString());
 127       }
 128       finally
 129       {
 130         running = false;
 131         exception = e;
 132         condition.signal();
 133       }
 134     }
 135     finally
 136     {
 137       lock.unlock();
 138     }
 139   }
 140
 141   public void start()
 142   {
 143     lock.lock();
 144     try
 145     {
 146       if (running)
 147         throw new IllegalStateException("Consumer instance " + id + " is already running!");
 148
 149       log.info("{} - Starting - consumed {} messages before", id, consumed);
 150       running = true;
 151       exception = null;
 152       executor.submit(this);
 153     }
 154     finally
 155     {
 156       lock.unlock();
 157     }
 158   }
 159
 160   public synchronized void stop() throws InterruptedException
 161   {
 162     lock.lock();
 163     try
 164     {
 165       if (!running)
 166         throw new IllegalStateException("Consumer instance " + id + " is not running!");
 167
 168       log.info("{} - Stopping", id);
 169       consumer.wakeup();
 170       condition.await();
 171       log.info("{} - Stopped - consumed {} messages so far", id, consumed);
 172     }
 173     finally
 174     {
 175       lock.unlock();
 176     }
 177   }
 178
 179   @PreDestroy
 180   public void destroy() throws ExecutionException, InterruptedException
 181   {
 182     log.info("{} - Destroy!", id);
 183     log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
 184   }
 185
 186   public boolean running()
 187   {
 188     lock.lock();
 189     try
 190     {
 191       return running;
 192     }
 193     finally
 194     {
 195       lock.unlock();
 196     }
 197   }
 198
 199   public Optional<Exception> exitStatus()
 200   {
 201     lock.lock();
 202     try
 203     {
 204       if (running)
 205         throw new IllegalStateException("No exit-status available: Consumer instance " + id + " is running!");
 206
 207       return Optional.ofNullable(exception);
 208     }
 209     finally
 210     {
 211       lock.unlock();
 212     }
 213   }
 214 }