Support host/path rules evaluated by AWS ALB

[hjacobs]

ALB can now do host-based routing. https://aws.amazon.com/blogs/aws/new-host-based-routing-support-for-aws-application-load-balancers/

This would allow configuring ALB without an extra HTTP router (like Skipper).

The rule limit is 75 so this setup might not work for everybody...

[alexkops]

I don't know if it's feasible or not, but would it be possible to default to ALB and only use Skipper if needed (rules are exceeded)? Transparently for the user?

[hjacobs]

@alexkops in theory yes, we could even transparently create more ALBs on reaching the AWS rule limit. We have to check whether this makes sense for us in Zalando as Skipper also provides detailed metrics and potentially more features in the future.

[hjacobs]

Also the networking part needs to be figured out as the ALB has to connect to the Kubernetes service which only has an internal ClusterIP.

[szuecs]

This is a bigger task and we have no reason right now to work on this, because we use https://github.com/zalando/skipper as ingress implementation to get metrics and more for different applications.

[hjacobs]

This came up again yesterday when @mikkeloscar and I talked with the AWS EKS team. The CoreOS ALB Ingress Controller has host/path routing, but we already solved other problems in our controller and it would potentially be easier to add host/path routing here instead of supporting CoreOS' controller which sets us back in some dimensions (e.g. SSL autodiscovery, easy cleanup).