@Override
    public String toString() {
        return "SharedKafkaProducerImpl{" +
                "sharedKafkaProducerIdentity=" + sharedKafkaProducerIdentity +
                ", isSuperseded=" + isSuperseded +
                ", useCounter=" + useCounter +
                '}';
    }
May close the wrapped {@link KafkaProducer} if it is deemed to no longer be needed.
stroom-kafka/stroom-kafka-impl/src/main/java/stroom/kafka/impl/SharedKafkaProducerImpl.java