Const ExperimentalThe subdomain portion of www.east.mydomain.co.uk is east. If the domain has multiple levels of subdomain, such as sub2.sub1.example.com, the subdomain field should contain sub2.sub1, with no trailing period.
This attribute is experimental and is subject to breaking changes in minor releases of @opentelemetry/semantic-conventions.
The subdomain portion of a fully qualified domain name includes all of the names except the host name under the registered_domain. In a partially qualified domain, or if the qualification level of the full name cannot be determined, subdomain contains all of the names below the registered domain.