Many to one relationship for VirtualServerRoute and VirtualServer

[golpa]

Is your feature request related to a problem? Please describe.
We deploy multiple websites and have certain common sub paths across all of them. Currently we have to duplicate these sub paths for each site.

For example we have:
http://site1/commonPath1
http://site1/commonPath2
http://site2/commonPath1
http://site2/commonPath2

Currently we we have to deploy 4 resource for the above setup (2 VirtualServers and 2 VirtualServerRoutes). This multiplies rather quickly if you have many sites and many common sub paths.

The reason for this is that the Host field in a VirtualServerRoute has to match the Host field in a VirtualServer.

Describe the solution you'd like
If possible, it would be nice to remove the restriction to require a Host field in a VirtualServerRoute allowing that route to be used in any VirtualServer that includes it. This would allow us to create routes for the common sub paths once and include them in every VirtualServer as necessary.

Describe alternatives you've considered
We tried to use wildcard domains but the restriction is the same. For example we tried to define the VirtualServer as site.domain and the VirtualServerRoute as "*.domain" but the ingress controller considers this an invalid configuration.

Additional context
Full sample setup we currently use:

apiVersion: k8s.nginx.org/v1
kind: VirtualServer
metadata:
  name: site1
spec:
  host: site1.domain
  upstreams:
    - name: site1App
      port: 80
      service: site1_app_service
  routes:
    - path: /
      proxy:
        upstream: site1App
    - path: /commonPath
      route: site1CommonPath
---
apiVersion: k8s.nginx.org/v1
kind: VirtualServerRoute
metadata:
  name: site1CommonPath
spec:
  host: site1.domain
  subroutes:
  - action:
      proxy:
        upstream: myCommonApp
    path: /commonPath
  upstreams:
  - name: myCommonApp
    port: 80
    service: my_common_app_service
---
apiVersion: k8s.nginx.org/v1
kind: VirtualServer
metadata:
  name: site2
spec:
  host: site2.domain
  upstreams:
    - name: site2App
      port: 80
      service: site2_app_service
  routes:
    - path: /
      proxy:
        upstream: site2App
    - path: /commonPath
      route: site2CommonPath
---
apiVersion: k8s.nginx.org/v1
kind: VirtualServerRoute
metadata:
  name: site2CommonPath
spec:
  host: site2.domain
  subroutes:
  - action:
      proxy:
        upstream: myCommonApp
    path: /commonPath
  upstreams:
  - name: myCommonApp
    port: 80
    service: my_common_app_service

Instead of the above it would be nice to have the following setup where we declare the VirtualServerRoute once and use it for both VirtualServers

apiVersion: k8s.nginx.org/v1
kind: VirtualServer
metadata:
  name: site1
spec:
  host: site1.domain
  upstreams:
    - name: site1App
      port: 80
      service: site1_app_service
  routes:
    - path: /
      proxy:
        upstream: site1App
    - path: /commonPath
      route: commonPath
---
apiVersion: k8s.nginx.org/v1
kind: VirtualServer
metadata:
  name: site2
spec:
  host: site2.domain
  upstreams:
    - name: site2App
      port: 80
      service: site2_app_service
  routes:
    - path: /
      proxy:
        upstream: site2App
    - path: /commonPath
      route: commonPath
---
apiVersion: k8s.nginx.org/v1
kind: VirtualServerRoute
metadata:
  name: commonPath
spec:
  # host: site1.domain <-- alternative to removing would be to support "*.domain" to match to both VirtualServers
  subroutes:
  - action:
      proxy:
        upstream: myCommonApp
    path: /commonPath
  upstreams:
  - name: myCommonApp
    port: 80
    service: my_common_app_service

[brianehlert]

Thank you! Converting this to a discussion to gather feedback and then we will take the results back to an issue if we decide to move forward.

[brianehlert]

I see multiple possible issues/ideas wrapped up inside of this.

Issue 1 - we have lots of VirtualServers defined, we do this because of hostname, TLS, and possibly other specific server level settings that need to be unique per hostname.
Issue 2 - we want to be able to match hostname / host using regex or an array of names with VirtualServer / VirtualServerRoute. Wildcard server in server.domain pattern is not flexible enough.
Issue 3 - Can Host be optional in VirtualServerRoute.

Anyone have other possible ideas here?

[brianehlert]

I am curious if this can be addressed in some way by #4092
Or if the use cases are simply so incredibly different.
But it seems to be a cross namespace version of 4092 as I continue to think about it.

[golpa]

I think fundamentally #4092 is trying to address a different problem than this. #4092 is addressing the problem of:

Given an existing VS I don't want to modify it every time a new VSR is added

Let's call that the top down approach. This feature request is similar but in reverse. Let's call it the bottom up approach:

Given a VSR I don't want to modify it anytime a VS wants to make use of it.

In the proposed solution from #4092 I think the bottom up approach is still not possible because the VSRs are tied to the VS via host.

Let's say entity 1 develops a generic VSR and wishes to make it available to any entities that create VS. Even with the proposed solution the VS has to contact entity 1 and ask for a VSR to be created for their specific VS because the host for the VS and VSR have to match.

So for every new VS we still have to create a new VSR even though they all point to the same underlying PODs.

This feature request is asking for the VSR entity to be able to create a generic VSR once and let any VS entity use it without having to ask the VSR entity to be involved.

The proposed solution in #4092 can be modified to include this feature as well by simply removing the requirement that the VSR include a host field.

Put it one other way the title #4092 is

Make it easier to "attach" a VirtualServerRoute to a VirtualServer without requiring that the VirtualServer be modified

following the same wording the title of this request would be

Make it easier to "attach" a VirtualServerRoute to a VirtualServer without requiring that the VirtualServerRoute be modified