@Override
        public Node provide() {
            if (metadataManager.isReady()) {
                if (metadataManager.usingBootstrapControllers()) {
                    return metadataManager.controller();
                } else if (metadataManager.nodeById(nodeId) != null) {
                    return metadataManager.nodeById(nodeId);
                }
            }
            metadataManager.requestUpdate();
            return null;
        }
Provides the least loaded broker, or the active kcontroller if we're using
bootstrap.controllers.
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java