protected int getIndex(HostResource host) {
        int i = 0;
        for (Service s : host.getServices()) {
            if (s.getServiceType().equals(getServiceType()) && (s != this)) {
                i++;
            }
        }
        return i + 1;
    }
Computes a number that identifies the service on the given
host. The number of services of the same type (Class) is
counted and the number is returned.

@param host the host on which the service will run
@return id number for the given service.
config-model/src/main/java/com/yahoo/vespa/model/AbstractService.java