@Override
    public boolean equals(Object o) {
        if (!(o instanceof ProducerIdsImage)) return false;
        ProducerIdsImage other = (ProducerIdsImage) o;
        return nextProducerId == other.nextProducerId;
    }
The next producer ID, or -1 in the special case where no producer IDs have been issued.
metadata/src/main/java/org/apache/kafka/image/ProducerIdsImage.java