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
<[email protected]<mailto:[email protected]>> 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)
<[email protected]<mailto:[email protected]>> 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
<[email protected]<mailto:[email protected]>> 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
