@Override
    public HostSpec allocateHost(String alias) {
        List<Host> defaultHosts = freeNodes.get(defaultHostResources);
        if (defaultHosts.isEmpty()) throw new IllegalArgumentException("No more hosts with default resources available");

        Host newHost = freeNodes.removeValue(defaultHostResources, 0);
        return new HostSpec(newHost.hostname(), Optional.empty());
    }
Returns the current allocations of this as a mutable map
config-model/src/main/java/com/yahoo/config/model/provision/InMemoryProvisioner.java