Collector fails to start when system detector cannot obtain FQDN of the host

[dmitryax]

Problem description
If we have OTel Collector with system detector enabled (resource detection processor), running on a VM that cannot provide fully qualified domain name for a reason, the collector is failing to start. The detector tries to set FQDN to host.name resource attribute, but OTel conventions don't specify that it has to be FQDN. So I don't see a reason why it should be failing.

Suggested solutions
I see two options to solve the problem:

1. If FQDN cannot be provided by the system, fall back to os.Hostname()
2. Introduce another resource attribute, e.g. host.fqdm which (if present) will always contain fully qualified domain name of the host.

@jrcamp @mx-psi @tigrannajaryan thoughts?

[tigrannajaryan]

If FQDN cannot be provided by the system, fall back to os.Hostname()

This sounds right to me given that Otel conventions say:

host.name - Name of the host. On Unix systems, it may contain what the hostname command returns, or the fully qualified hostname, or another name specified by the user.

Regarding your second point:

Introduce another resource attribute, e.g. host.fqdm which (if present) will always contain fully qualified domain name of the host.

Yes, we can do it in the future if necessary. For now I would suggest to go with option 1.

[mx-psi]

I opened #3099 to fix this using option 1, PTAL