High level Kafka Consumer Only Consumes Half Of Messages Sent By Producer - apache-kafka

Question

I have implemented a high level consumer per the example page: https://cwiki.apache.org/confluence/display/KAFKA/Consumer+Group+Example
When the code runs, it only consume half of the messages produced. I have a basic 3 node zookeeper cluster and 2 kafka brokers. When I run the simple consumer code (not high level consumer), all the messages are consumed. Any ideas will be appreciated.
Consumer code
public void run() {
Map<String, Integer> topicCountMap = new HashMap<String, Integer>();
topicCountMap.put("test", 2);
Map<String, List<KafkaStream<byte[], byte[]>>> consumerMap = consumer.createMessageStreams(topicCountMap);
List<KafkaStream<byte[], byte[]>> streams = consumerMap.get("test");
executor = Executors.newFixedThreadPool(2);
int threadNumber = 0;
for (final KafkaStream stream : streams) {
executor.submit(new Consumer(stream, threadNumber));
threadNumber++;
}
}
private static ConsumerConfig createConsumerConfig() {
Properties props = new Properties();
props.put("zookeeper.connect", "zookeeper01:2181,zookeeper02:2181,zookeeper03:2181");
props.put("group.id", "Consumers");
props.put("zookeeper.session.timeout.ms", "10000");
props.put("enable.auto.commit", "true");
props.put("zookeeper.sync.time.ms", "1000");
props.put("value.deserializer","org.apache.kafka.common.serialization.StringDeserializer");
props.put("auto.commit.interval.ms", "500");
return new ConsumerConfig(props);
}