We occasionally discuss this issue but haven't tackled it yet. I think the main issue is just that duplicate origins have been allowed since the beginning, and now everyone's Traffic Ops could be littered with duplicate origins. Also, depending on the config of the duplicate delivery services, the origins might not be in conflict at all (if they don't have different topology constraints). I would love for us to just add a uniqueness constraint, but there would need to be a fair amount of warning to the community before doing so and might invalidate a significant amount of valid use cases. Operators would need time to make DNS CNAME records for the duplicate origins and update their DSes to use the different CNAMEs.
I think as a good first step to eliminating the use of duplicate origins altogether, we should identify which "topology constraints" actually cause conflicting config when used with duplicate origins and prevent creating DSes with duplicate origins _if it would cause a conflict with an existing DS that uses the same origin_. For instance, I believe an HTTP and DNS-type DS can live happily side-by-side using the same origin (probably need different routing_names?), but scenarios like HTTP and HTTP_LIVE, or DNS and HTTP_NO_CACHE sharing the same origin will cause conflicts for sure. So maybe we can start by making sure the DS types "match" when using the same origin: HTTP + DNS: possibly good, if they have different routing names? HTTP_LIVE + HTTP_LIVE_NATNL: bad HTTP_NO_CACHE + [any other type]: bad HTTP_LIVE + HTTP: bad etc. There are most likely other conflict scenarios that don't involve the DS types, but I think this would be a good start. In the future with Delivery Service Topologies (aka Flexible Cachegroups aka Bring Your Own Topology), we might be able to prohibit assigning a DS to a Topology if the DS's origin is already used by another DS in a different Topology. - Rawlin On Mon, Dec 17, 2018 at 10:52 AM Fieck, Brennan <brennan_fi...@comcast.com> wrote: > > As some of you may be aware, `parent.config` files generated by Traffic Ops > can vary wildly when an origin is assigned to multiple Delivery Services. > This results in undefined behavior. I'm told that the conflict only happens > when two Delivery Services with different "topology requirements" use the > same origin, whatever that means (content routing type?). Regardless, the > issue should be addressed. The obvious solution is to put in place a database > constraint that prevents an origin from being assigned to more that one > Delivery Service with API checks in place that would provide helpful error > messages when an attempt is made to violate the constraint. However, would > that mess with things like Multi-Site Origin? Or is it just not viable for > some other reason? If it is a good solution, I'm prepared to work on a fix > that utilizes it.
