sap_swpm: Should we make NW_DI_Instance.virtualHostname (maybe more) optional?

[berndfinger]

In templates/inifile_params.j2, we are setting NW_DI_Instance.virtualHostname unconditionally to sap_swpm_aas_instance_hostname if section nw_config_additional_application_server_instance is contained in sap_swpm_inifile_sections_list.

However, there are cases where we do not want NW_DI_Instance.virtualHostname, so we could make this optional, as also already mentioned in the comment in the line before this one (Leave empty to use the existing host name). Suggested parameter:
sap_swpm_use_virtualhostname.

If set to true, we use the current code. If set to false, we comment out this line.

I also successfully tested the following workaround: Configure:

sap_swpm_inifile_parameters_dict:
  NW_DI_Instance.virtualHostname: ''

for setting NW_DI_Instance.virtualHostname to an empty string. So we are already flexible and can replace any parameter setting made by templates/inifile_params.j2 with a new parameter setting of our choice.

[sean-freeman]

Personally, I would suggest by default always Virtual Hostnames as a best practice. I suggest we ask @rob0d for his opinion

[rob0d]

I think @berndfinger is right.
NW_DI_Instance.virtualHostname should be set only when installing using virtual hostnames.
This is the case only when SAPINST_USE_HOSTNAME is set on command line and this is driven by sap_swpm_virtual_hostname parameter.
I have installed quite a few AASes with the current settings with the value set and it had no negative impact. I think that SWPM ignores this value unless SAPINST_USE_HOSTNAME is set. However, to be more accurate it should be set only when sap_swpm_virtual_hostname is set.
The best test would be to run AAS install without SAPINST_USE_HOSTNAME and check if NW_DI_Instance.virtualHostname is present in the param file or not.