@Override
    public LeastLoadedNode leastLoadedNode(long now) {
        // Consistent with NetworkClient, we do not return nodes awaiting reconnect backoff
        for (Node node : metadataUpdater.fetchNodes()) {
            if (!connectionState(node.idString()).isBackingOff(now))
                return new LeastLoadedNode(node, true);
        }
        return new LeastLoadedNode(null, false);
    }
Raise an unsupported version error on the next request if it matches the given matcher.
If the matcher does not match, {@link KafkaClient#send(ClientRequest, long)} will throw IllegalStateException.
@param matcher The request matcher to apply
clients/src/test/java/org/apache/kafka/clients/MockClient.java