Validate DC name does not contain a period

[armon]

DC names should match [a-zA-Z0-9-_]+

[andrewwatson]

What should happen if it doesn't match that character class? Just drop the bad characters? Should it warn you first or fail completely?

[armon]

Yeah fail the validation, agent will refuse to start.

[blalor]

Why was this a problem? The change is undocumented, and it just broke my Consul cluster: we were using DCs like us-east-1.aws.prod.

[blalor]

Corollary: this issue is referenced in the changelog, but the impact is not.

[armon]

@blalor It should have broken the DNS parser to have a DC like that. Were you using the DNS interface at all?

We must have mistakenly failed to put it in the change log.

[blalor]

No, we weren’t using the DNS interface, yet. I see where that would cause problems, but I’d like to have seen the DC treated as an opaque string by the resolver. This also implies that dots in node names will also cause problems, correct?

[armon]

I think a dot in a node name is fine. I can look into changing the resolver to remove this limitation.