Allow underscores to be used in template-name

[zxiiro]

The underscore _ character used to be a valid character. The regex
should allow the use of this character.

[tykeal]

This looks good to me. I'll note that we use the '_' in several of our template names so dropping it breaks us.

[askb]

LGTM

[olivergondza]

The original code comes from https://github.com/jclouds/jclouds/blob/master/core/src/main/java/org/jclouds/predicates/validators/DnsNameValidator.java.

As you have noticed, the validator was essentially inefficient until fixed recently so that might be the reason you ware permitted to put underscores there. Frankly, I have no idea where did I get the original regex but it feels wrong at least in accepting uppercase letters. I have not studied the internet hostname specification at length, but it appears hostnames (template name is used as part of the hostname) must not contain uppercase letters or underscores.

From the pragmatic standpoint, this is what we ask openstack to name the server and apparently it does the necessary validation/correction before using it as OS hostname. If it can translate the server name into a valid hostname, then I do not think we have to worry about validity of the template name all that much.

I have just tested OpenStack accepts insanities like /*[$]*/ in server name and actually uses it for resource name while linux hostname is purged of all disallowed characters. Would you be ok to relax the restrictions to https://github.com/jenkinsci/jenkins/blob/c926d5b79f4bdd8b9e744035473a20f5ceb4926c/core/src/main/java/jenkins/model/Jenkins.java#L3894-L3919 (the template name can be used as url chunk so better not have it completely unrestricted)?

[zxiiro]

@olivergondza I hadn't thought about the DNS issue. I tend to agree with you that if template-name is used as hostname then what we pass in as input should match output in openstack. Perhaps I can flip this patch to restrict the upper case characters?

[olivergondza]

@zxiiro, that is what used to be a concern back in jclouds days, though I question if that still is a concern today. As I said, based on my testing, OpenStack does the right thing for us. My suggestion is to make the name sane for us and rely on OpenStack sanitation until we have a report that it does not work in certain cases and then and only then handle those cases. At least, we would know why we are restricting something...

[zxiiro]

@olivergondza that's fine with me. In this case I'll just close this PR as it's not necessarily a problem and my team can resolve it on our side as a policy.

[zxiiro]

Ah I wasn't thinking about the underscore patch in my previous reply. @olivergondza feel free to reopen and accept the patch if you want to allow underscores.

I am fine with whatever you choose as long as it doesn't break on the backend. I can confirm that underscores (_) are translated to dashes (-) by openstack in the backend so it should be safe to use.

[olivergondza]

Fixed in f043930. Thanks for pointing this out.