Support having multiple VirtualService objects

[dsbos]

Summary

Rollout does not seem to support having (specifically, updating weights in) multiple VirtualService objects.

Per the Rollout specification currently at
https://argoproj.github.io/argo-rollouts/features/specification/, in particular, this part:

        # Istio traffic routing configuration
        istio:
          virtualService: 
            name: rollout-vsvc  # required
            routes:
            - primary # At least one route is required

it does support having multiple Istio HTTPRoute sub-objects in a VirtualService (via having that routes member be a list of HTTPRoute names).

However, Rollout does not support having multiple VirtualService objects (since the value of member virtualService is single object)

If member virtualService, which currently gives one sub-object specifying a VirtualService, were replaced with a member (e.g., virtualServices) listing multiple such specification sub-objects, then Rollout would support having multiple VirtualServices (each with its own name and own list of HTTPRoute names).

For backward compatibility, Rollout could keep virtualService when adding virtualServices (making it a semantic error to specify both).

Use Cases

This enhancement is needed to support Istio-based setups in which a service's routes are given in multiple VirtualService objects rather than just a single one.

(Recall that Istio allows splitting up a service's routing into multiple VirtualService objects. Also, note that mapping from ingress host names to services might involve multiple host names, per–URI-path routing, and multiple target services. For multiple routes going to the same target service, sometimes splitting into multiple VirtualService objects makes things (e.g., matching rules) much simpler.)

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Message from the maintainers:

Impacted by this bug? Give it a 👍. We prioritize the issues with the most 👍.

[gaurav517]

👍

[sadovnikov]

Until one-year-old istio/istio#22997 is resolved it's necessary to create separate VirtulServices for ingress and mesh-internal requests. With the single value of istio. virtualService users cannot apply canary deployment on all traffic

[huikang]

Our team has a PR to enable this. Will submit a PR soon.

[shakti-das]

Update: We are testing out the PR internally. It will be out for review mostly by next week.

[shakti-das]

Hi @jessesuen, could you please assign this to @darshanhs09. He will be sending out a PR for it soon. Thank you.