Support more than 2 Istio HTTPRouteDestinations in the Canary rollout

[wentwog]

Currently the Canary rollout requires that Istio VirtualService's HTTPRoute must have exactly 2 HTTPRouteDestinations.
Support having more HTTPRouteDestinations.

Use Cases

Migrating to Istio, we have a legacy system to which we route some percentage of traffic, e.g.:

• Istio Stable: 50%
• Istio Canary: 30%
• Legacy: 20%

When a new service version gets rolled out, we'd like ArgoRollouts to switch the weights only for the first two HTTPRouteDestinations.
Note, Stable + Canary weight might not be 100% in this case.
The Legacy weight is changed manually.

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[pparth]

It is rather restrictive to have to use exactly 2 Route Destinations, unless we are missing something.

[agrawroh]

Since I already touched some of the code for Argo integration with Istio VS in one of my other PRs, I could work on this one. We have a similar requirement and it'll be pretty cool to get it done.
cc @huikang

[pparth]

So, is there an ETA about this?

[agrawroh]

Created a PR for this: #1420

Would appreciate any feedback/comments.

[angeloslenis]

Any updates here?

[github-actions]

This issue is stale because it has been open 60 days with no activity.

[github-actions]

This issue is stale because it has been open 60 days with no activity.

[jonwinton]

Hello! This is an issue I've come across that I'm interested in solving for our org. @agrawroh I saw from your PR that there was a question about the approach to the design and you had a suggestion:

One proposal is to add an optional httpRoutes which will be an array of objects similar to the tlsRoutes and gradually deprecate the use of routes over time. In the beginning, we can enforce the use of only one i.e either routes or httpRoutes. I proposed this to @jessesuen as well.

To pick this up, would you recommend following this route? Or do you think the approach of maxWeight is the appropriate?

[agrawroh]

Hello! This is an issue I've come across that I'm interested in solving for our org. @agrawroh I saw from your PR that there was a question about the approach to the design and you had a suggestion:

One proposal is to add an optional httpRoutes which will be an array of objects similar to the tlsRoutes and gradually deprecate the use of routes over time. In the beginning, we can enforce the use of only one i.e either routes or httpRoutes. I proposed this to @jessesuen as well.

To pick this up, would you recommend following this route? Or do you think the approach of maxWeight is the appropriate?

@jonwinton Yes, converting routes to an object as suggested would probably be the right way to do it. If you want to give it a shot, I'm more than happy to review :)