Before this, during a call to the docker resolver, we would generate
span wrappers for each HTTPRequest correctly, however, as the docker
resolver reaches out to the docker authorizer, it could create HTTP
requests (for fetching tokens) that would not be wrapped in any span.
This can result in rather confusing traces, e.g. something like:
remotes.docker.resolver.HTTPRequest
HTTP HEAD (fetch index, fails with 401)
HTTP GET (fetch token)
remotes.docker.resolver.HTTPRequest
HTTP HEAD (fetch index)
remotes.docker.resolver.HTTPRequest
HTTP GET (fetch manifest)
By adding a span into the FetchToken, this trace becomes a little easier
to consume:
remotes.docker.resolver.HTTPRequest
HTTP HEAD (fetch index, fails with 401)
remotes.docker.resolver.FetchToken
HTTP GET (fetch token)
remotes.docker.resolver.HTTPRequest
HTTP HEAD (fetch index)
remotes.docker.resolver.HTTPRequest
HTTP GET (fetch manifest)
Signed-off-by: Justin Chadwell <me@jedevc.com>
