ncm-network core schema: allow realhostname to be a short hostname

[jouvin]

• Allow better support of software like Ceph where it is the recommended setting

This change is backward compatible but relaxes the requirements on realhostname property. I also checked the template-library-standard, template-library-os, template_library_core and template-library-grid repositories, as well as configuration-modules-core. realhostname is not referenced in any of them (except ncm-network schema definition intemplate_library_core) . Only hostname is set in template-library-standard but this property is not affected by this PR.

[jrha]

I'm not really sure why realhostname was added, but it's definitely supposed to be a FQDN, the component uses it like this:

my $hostname = $nwtree->{realhostname} || "$nwtree->{hostname}.$nwtree->{domainname}";

ncm-network/src/main/perl/network.pm#L1973C5-L1973C91

[jrha]

We don't use realhostname at RAL, what's the use-case?

[jrha]

Also can you provide a reference to the recommendation for short hostnames in the Ceph docs please?

[jouvin]

@jrha not sure why you are saying this. What the component does it to define the host name based either on the hostname property with the domain name appended or the realhostname property used litteraly. realhostname, as the name suggests, is something that must be used as it is provided without any processing. The only requirement is that it is a valid host name value and both forms are valid (and as pointed out by the docs I mentionned, FQDN is not favoured when a machine has multiple interfaces/adresses like it is almost always the case on a Ceph machine.

[jouvin]

At the end I don't care whether we relax the types allowed or add a new property like shortrealhostname (it seems to me it is an overkill if we look at the current usage of realhostname). My main point is: the hostname and realhostname properties are used by the component to pass a valid value to define the actual host name but with the current schema we don't support all the valid values at the Linux level as there is no way to use a short hostname if we want, whatever the reason. IMO, this should be fixed.

[jouvin]

Unit tests are failing in ncm-spma so it doesn't seem to be related. ncm-network tests are ok.

[stdweird]

i once proposed the idea to add methods to ccm to extract the fqdn hostname and make it similar to realhostname || hostname.domainname, so this could be used in components that now only use hostname.domainname.
so i don't care much tbh, we also don;t use it in our profiles. but be aware that some components use the fqdn as hostname.