presto-kafka/src/main/java/io/prestosql/plugin/kafka/KafkaSimpleConsumerManager.java/KafkaSimpleConsumerManager/tearDown
class KafkaSimpleConsumerManager:    @PreDestroy
    public void tearDown()
    {
        for (Map.Entry<HostAddress, SimpleConsumer> entry : consumerCache.asMap().entrySet()) {
            try {
                entry.getValue().close();
            }
            catch (Exception e) {
                log.warn(e, "While closing consumer %s:", entry.getKey());
            }
        }
    }