HTTPRoute - routing to a large number of urls?

[meastp]

From kubernetes-sigs/gateway-api#2583

Hi,

I want to use the Gateway API for routing with HTTPRoute. The service consists of a few thousand datasets (=postgres database for each dataset), and the url to each dataset use an uuid to identify the dataset, like this:

/app/uuid1/data
/app/uuid2/data
...
/app/uuidN/data

During normal operation, I just route /app/* to my service, of course.

I'm wondering how this will work during an upgrade, because I would like to be able to use a canary-style upgrade where I change the routing to individual datasets to point to the new version for tesing.
In case of database schema upgrades, I also want to migrate the datasets one-by-one to avoid downtime on multiple datasets at once.

I guess all the urls need to be typed out individually in the manifest then, and which service they point to?
How efficient will this be if there are 100s or 1000s urls?

I am aware of the precedence-prefix-precedence rule, which would cut the max number of paths in half.

[pleshakov]

@meastp

How efficient will this be if there are 100s or 1000s urls?

is the concern here if NGINX is efficient at matching an incoming request to the correct location? So that no extra latency is seen by the clients?

[meastp]

My first concern would be if nginx/gateway api has limits on the number of routes/matches/paths? If so, perhaps what I'm asking needs to be solved a specific way to be efficient or even possible?

If this is possible, then I wonder how it will affect the latency, yes. :)

[pleshakov]

My first concern would be if nginx/gateway api has limits on the number of routes/matches/paths?

Gateway API has limits:

• https://github.com/kubernetes-sigs/gateway-api/blob/0f040de255887d80a7df2a9fdc7278a08b38de9c/apis/v1/httproute_types.go#L119
• https://github.com/kubernetes-sigs/gateway-api/blob/0f040de255887d80a7df2a9fdc7278a08b38de9c/apis/v1/httproute_types.go#L192

For your case, it should be possible to start with a single rule like below:

  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /coffee/1
    - path:
        type: PathPrefix
        value: /coffee/2
    - path:
        type: PathPrefix
        value: /coffee/3
    backendRefs:
    - name: coffee-new
      port: 80
  - matches:
    - path:
        type: PathPrefix
        value: /coffee
    backendRefs:
    - name: coffee-old 
      port: 80

Once you hit 8 matches per rule limit, you can add more rules. Once you hit 16 rules per HTTPRoute limit, you can add more HTTPRoutes.

If so, perhaps what I'm asking needs to be solved a specific way to be efficient or even possible?

I don't see a different way

If this is possible, then I wonder how it will affect the latency, yes. :)

NGINX is pretty efficient at matching requests for prefix/exact matches. Internally it uses a radix-tree-like data structure. The request matching latency will be negligible compared to latency for proxying the request to the backend.

[meastp]

Thank you - I'll just have to work around the limits :)