private boolean matches(ClusterSpec nodeCluster, ClusterSpec requestedCluster) {
        if (requestedCluster.group().isPresent()) // we are requesting a specific group
            return nodeCluster.equals(requestedCluster);
        else // we are requesting nodes of all groups in this cluster
            return nodeCluster.satisfies(requestedCluster);
    }
Creates a static host provisioner which will fall back to using the given provisioner
if a request is made for nodes in a cluster which is not present in this allocation.
configserver/src/main/java/com/yahoo/vespa/config/server/provision/StaticProvisioner.java