No problem, Eric. I appreciate a good brainstorming. Really the Seattle-Denver-Boston example I gave was just to illustrate the idea of the feature; I'm not sure we'd actually go with a Geo Steering DS architecture that dispersed.
Steering DSes aren't actually assignable to specific cachegroups, because the assignments of the target DSes are what's actually used in order to find a cache that supports the target DS. As long as the target DSes are assigned to all cache groups, the client will be routed to an optimal edge cache. If the targets are geo-ordered, then the client's first option is to request a target DS with an Origin that is also optimal to that edge cache. I think I might've confused the way I worded the problem initially. The target DSes should always be ordered by distance between the routed-to cachegroup and the Origin. That way a client in Seattle that was routed to an edge in Boston (if the Seattle and Denver CGs were down) would first request an Origin in Boston not Seattle. That way traffic wouldn't be be crossing the country twice. Does that make more sense? - Rawlin On Wed, Feb 28, 2018 at 7:39 AM, Eric Friedrich (efriedri) <efrie...@cisco.com> wrote: > Thanks Rawlin- > Thanks for bearing with me. I’m thinking through this and wanted to > brainstorm a little. > > What’s the benefit of going to the Boston edge cache to get the Seattle or > Denver DeliveryServices? > - If you already have redundant origins in Boston, you’re protected against > failure of a single origin. > - If both Boston origins fail, the client would be routed to Denver and hit > the local Denver origins. > - If both Boston origins are down, then you wouldn’t be able to get Boston > content in Denver anyway > - But clients in Boston would now need to hit the Denver edges, perhaps > overloading that CG. If this is a failure case you want to address, maybe we > could do something like the following: > > Would it be possible to create multiple levels of steering delivery services? > - Top Level: Client Steering DS > (tr.nbc.cdn.customer.com<http://tr.nbc.cdn.com>) - assigned to all CG. Does > GeoOrdering based on client proximity to assigned cache groups of the target > DS' > - Target 1: Boston Client Steering DS > (tr.bos-nbc.cdn.customer.com<http://tr.boston-nbc.cdn.customer.com>) - > assigned only to Boston CG. Ranked steering policy > - Target 1.1: Boston Live DS > (tr.bos-bos-nbc.cdn.customer.com<http://tr.bos-bos-nbc.cdn.customer.com>), > rank=1 > - Target 1.2: Denver Live DS > (tr.den-bos-nbc.cdn.customer.com<http://tr.den-bos-nbc.cdn.customer.com>), > rank=2 > - Target 1.3: Seattle Live DS > (tr.sea-bos-nbc.cdn.customer.com<http://tr.sea-bos-nbc.cdn.customer.com>), > rank=3 > > - Target 2: Denver Client Steering DS > (tr.den-nbc.cdn.customer.com<http://tr.denver-nbc.cdn.customer.com>) - > assigned only to Denver CG > - Target 3: Seattle Client Steering DS > (tr.seat-nbc.cdn.customer.com<http://tr.seattle-nbc.cdn.customer.com>) - > assigned only to Seattle CG > > The goal would be this order of DS’s returned to the client > Location: [tr.bos-bos-nbc, tr.den-bos-nbc, tr.sea-bos-nbc, tr.den-den-nbc, > tr.sea-den-nbc, r.bos-den-nbc,…. ] > > Is this what are you ultimately looking for? > > This lets us choose CG and DS based on the location of the client relative to > the edge cache, rather than proximity of client to origin. Since the client > is talking to the edge cache and not the origin, this seems like a better > metric. Being able to compose Steering DS would also give us more flexibility > for other use cases in the future as well > > > > > On Feb 27, 2018, at 4:40 PM, Rawlin Peters > <rawlin.pet...@gmail.com<mailto:rawlin.pet...@gmail.com>> wrote: > > Hey Eric, > > In this example I'd think that all the target DSes would need to be > assigned to all 3 Cache Groups. That way the client could possibly use > any of the target DSes from the cachegroup they're routed to. But I > suppose that could change on a case-by-case basis where maybe the > target DSes are only assigned to cache groups that are close to their > origins. In that case I'd think a client in Seattle would possibly be > routed to an edge cache in Boston, which would optimize the connection > between the Boston edge cache and the Boston origin. But it might be > better to have the client connect to an edge cache in Seattle which > then retrieves the content from a Boston origin (although these are > both worst-case scenarios). > > As far as the content on the origins themselves go, they'd have to be > interchangeable from the client's perspective, but I'm not sure if it > would have to be identical or not. I imagine that would really depend > on what the steering DS is providing the client. > > - Rawlin > > On Tue, Feb 27, 2018 at 10:37 AM, Eric Friedrich (efriedri) > <efrie...@cisco.com<mailto:efrie...@cisco.com>> wrote: > In this example, what would be the assignments of delivery services to edge > Cache Groups? Are all 3DS’ assigned to all 3 Cache Groups? > > I’ll also assume that the content on the origins, while interchangeable from > a clients perspective, is not identical? (i.e. might contain regionalized > content?) > > —Eric > > > > > On Feb 23, 2018, at 5:40 PM, Rawlin Peters > <rawlin.pet...@gmail.com<mailto:rawlin.pet...@gmail.com>> wrote: > > Hey folks, > > At Comcast we have a need to augment CLIENT_STEERING (also regular > STEERING while we're at it) to allow targets to be ordered/sorted > based upon the client's proximity to the origin of the target delivery > services. I'd like to get your feedback on my proposed design and > address any of your concerns. > > For HTTP_LIVE targets for instance, we'd like edge caches to ideally > retrieve/serve data from an Origin that is close to the client and > fall back to Origins that are farther and farther away. This allows > for increased redundancy while ordering optimal Origins (Delivery > Services) for a client to choose from. > > For example, I have 3 Origins in different locations: Seattle, Denver, > and Boston. I would create an HTTP_LIVE delivery service for each > origin and a CLIENT_STEERING delivery service with those delivery > services as targets. I would then like to have those targets ordered > based upon proximity to the client. So a client in Seattle would get > the list [Seattle, Denver, Boston], while a client in Boston would get > the list [Boston, Denver, Seattle]. > > To make things more complicated, I want to add a redundant origin in > each location and split traffic between them (like STEERING_WEIGHT > today) while taking into account the geo-ordering. I also want to be > able to force an ordering (like STEERING_ORDER today) among co-located > targets. > > In order to accomplish this I propose to: > 1. add two new steering types: GEO_ORDER and GEO_WEIGHT (by adding a > target of type GEO_*, a steering DS would then enable geo-ordering) > 2. associate a Delivery Service Origin with a latitude/longitude, > thereby associating a lat/long to a GEO_* target > > Item 1 is pretty straightforward and will also play nicely with the > current steering types (STEERING_ORDER and STEERING_WEIGHT). I've > completed a POC within Traffic Router that basically provides the > following ordering when mixing all 4 types in a single steering > delivery service: > - Negative STEERING_ORDER targets > - GEO_WEIGHT and GEO_ORDER targets, grouped by proximity to the > client, ordered by geo-order and the consistent-hashing from the > weightings > - STEERING_WEIGHT targets (consistent-hashed) > - Positive STEERING_ORDER targets > > Item 2 is not as straightforward because the simple thing would be to > just add an Origin Lat/Long field to the Delivery Service and call it > a day. However I don't think we should do that, and I'll dive more > into that in a separate thread (coming soon). > > Does anyone have questions/concerns about adding these new GEO_ORDER > and GEO_STEERING target types and geo-sorting them based upon > proximity to the client? Are you okay with the proposed ordering when > all the steering types are mixed together? > > - Rawlin > >
