Allow ip_hash for backends

[sajal]

The controller should accept some annotation to indicate client affinity, if so then set ip_hash in the upstream block.

[pleshakov]

We can solve it by solving a general problem of specifying a load balancing method: least_conn, ip_hash, general hash (https://www.nginx.com/resources/admin-guide/load-balancer/#method)

We can have an annotation and a Config map key for that:
nginx.org/default-lb-method / default-lb-method
If it's not set, the default round-robin method will be used.

Additionally, it makes sense to add an annotation that allows specifying a method per service, similar to https://github.com/nginxinc/kubernetes-ingress/tree/master/examples/rewrites.
`nginx.org/lb-method: "serviceName=service1 method=method1[;serviceName=service2 method=method2;...]"

Let me know what you think.

[sajal]

+1 for nginx.org/default-lb-method . Shall I attempt to implement it? Or wait for design to be settled?

Alternatively, you could look at the service's sessionAffinity to configure per-service lb-method.

"By default, the choice of backend is round robin. Client-IP based session affinity can be selected by setting service.spec.sessionAffinity to "ClientIP" (the default is "None")."

But this only gives you the option between ip_hash and the default round-robin.

[pleshakov]

@sajal

+1 for nginx.org/default-lb-method . Shall I attempt to implement it? Or wait for design to be settled?

That'd be great if you could add it.

Alternatively, you could look at the service's sessionAffinity to configure per-service lb-method... But this only gives you the option between ip_hash and the default round-robin.

I think it's better to add more options then the two options available with the service session Affinity property.

[sajal]

Will get my hands dirty and attempt to implement annotation and config map setting this week or weekend. For my PoC I simply hardcoded ip_hash; into the template.

[quasiben]

Is this still something being developed ?

[sajal]

I still need this for a service I need to migrate inside my Kubernetes cluster. However I currently do not have time to work on it for next few weeks.

I will post here when I do begin working on it. In case someone else is working on it in the meantime, please update this thread so we don't duplicate effort.