Enhancement Proposal: Multiple ALB Ingress Support for Canary Traffic Management

[n888]

Enhancement Proposal: Multiple ALB Ingress Support for Canary Traffic Management

Enable defining multiple AWS ALB Ingress objects within a single Rollout object, with all Ingresses progressing in unison for each canary step.

Related: #710

Summary

ArgoRollouts currently supports managing a single ALB Ingress object per Rollout object. This limitation poses a problem when a single Application is served using multiple ALB Ingress objects.

For example: Ingresses for an Internal and External network, when there are various EC2 / AWS Services that need to reach a service inside an EKS cluster.

Workarounds

An example workaround is to create multiple Rollout objects in an Application, one for each ALB Ingress object. This option puts the onus on the operator to ensure all of the Rollout objects are progressing/resumed together in the correct order, increasing the chance of human error.

This workaround also unnecessarily increases the overall Application Pod count by at least 1, since each additional Rollout creates a separate replicaset.

Another workaround is potentially using AnalysisTemplates to trigger child rollout objects, but this seems a bit too clunky.

Example Multi-ALB Patch

master...n888:argo-rollouts:master

The limitation was a deal-breaker for some of our internal organizations, and we have created a Multi-ALB patch to bridge the gap for now and to re-spark the idea to the community, which we have been running in production workloads for the past three months.

The logic is heavily modeled after the Multiple Nginx Ingress patch by @tperdue321 (Thank you!) rallyhealth#1

Components Modified

• Traffic Routing: Updates ALB data type to include a list of additionalIngresses
• SetWeight: SetWeight is now a stub function that calls SetWeightPerIngress which processes the additionalIngresses followed by the ingress
  • Returns errors encountered during any of the ingress weight modifications
• VerifyWeight: VerifyWeight is now a stub function that calls VerifyWeightPerIngress which processes the additionalIngresses followed by the ingress
  • Returns errors encountered during any of the ingress weight verifications
• Validators: Validates all available ingresses
• Rollout CRD: Updated to include trafficRouting.alb.additionalIngresses field

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[n888]

Resolved via #2639