[GitHub] [incubator-gobblin] vikrambohra commented on a change in pull request #2900: [GOBBLIN-1040] HighLevelConsumer re-design by removing references to …

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vikrambohra commented on a change in pull request #2900: [GOBBLIN-1040] HighLevelConsumer re-design by removing references to …
URL: https://github.com/apache/incubator-gobblin/pull/2900#discussion_r386547675
 
 

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 File path: gobblin-modules/gobblin-kafka-09/src/main/java/org/apache/gobblin/kafka/client/Kafka09ConsumerClient.java
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 @@ -160,14 +164,30 @@ public long getLatestOffset(KafkaPartition partition) throws KafkaOffsetRetrieva
 
     this.consumer.assign(Lists.newArrayList(new TopicPartition(partition.getTopicName(), partition.getId())));
     this.consumer.seek(new TopicPartition(partition.getTopicName(), partition.getId()), nextOffset);
-    ConsumerRecords<K, V> consumerRecords = consumer.poll(super.fetchTimeoutMillis);
-    return Iterators.transform(consumerRecords.iterator(), new Function<ConsumerRecord<K, V>, KafkaConsumerRecord>() {
+    return consume();
+  }
 
-      @Override
-      public KafkaConsumerRecord apply(ConsumerRecord<K, V> input) {
-        return new Kafka09ConsumerRecord<>(input);
-      }
-    });
+  @Override
+  public synchronized Iterator<KafkaConsumerRecord> consume() {
 
 Review comment:
   Underlying Kafka Consumer is not thread safe. consume() commitAsync(), committed() all try to acquire a lock (and they are different threads) the consumer throws a ConcurrentModificationException if it detects that the lock has been acquired by another thread.
   
       /**
        * Acquire the light lock protecting this consumer from multi-threaded access. Instead of blocking
        * when the lock is not available, however, we just throw an exception (since multi-threaded usage is not
        * supported).
        * @throws IllegalStateException if the consumer has been closed
        * @throws ConcurrentModificationException if another thread already has the lock
        */
       private void acquire() {
           ensureNotClosed();
           long threadId = Thread.currentThread().getId();
           if (threadId != currentThread.get() && !currentThread.compareAndSet(NO_CURRENT_THREAD, threadId))
               throw new ConcurrentModificationException("KafkaConsumer is not safe for multi-threaded access");
           refcount.incrementAndGet();
       }

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