Allow setting load balancer method and sticky using service annotations

[bakins]

My take on #940 - slightly modified.

As we are setting backend behavior, I think the annotations should be on the backend - the Kubernetes service.

Includes unit tests for sticky and drr. having issues getting integration tests running locally, but I'll figure that out and patch as needed.

[emilevauge]

Thanks @bakins 👍
@errm @dtomcej WDYT of setting these annotations on services instead ?

[dtomcej]

@emilevauge @bakins Kubernetes load balancer settings are officially set using service annotations. I think that using the same process for traefik would be beneficial :)

👍

[emilevauge]

LGTM!
Thanks @bakins
/cc @containous/traefik

[vdemeester]

LGTM 🦁

[errm]

Rebased on master

[errm]

LGTM

[hoeghh]

Will i be able to see any indication on the dashboard that a service is sticky? I have added the annotation, but nothing changes in the UI. Is it documented ?

[ldez]

@hoeghh Currently the dashboard doesn't display the sticky state.

You can call http://<your traefik url>/api/providers to get the full configuration.
ex: http://127.0.0.1:8080/api/providers

[hoeghh]

@ldez thanks, it works.

@dtomcej But not until i found out that the annotation should be on the service object, and not the ingress object. That just does not make any sense. Why would the annotation be on the service object? I get that not all Kubernetes variants have ingress (OpenShift) but still. The ingress object is there to tell the ingress controller how to act. The service is mostly used inside the cluster for endpoint lookups.

[dtomcej]

@hoeghh The reason the annotation is on the service is due to the ServiceType: LoadBalancer that most cloud providers implement to provide a software load balancer to the cluster. This is used instead of ingress, for instance, in AWS, will provision a new ELB. That is why those annotations are officially on the service. :)

[bakins]

@hoeghh An ingress can reference several services and a service can be in more than one ingress. One may need to set sticky, circuit breaker, or other options on a per service basis.