Replacement for Ribbon LB

[ArtyomGabeev]

Enhancement

As I understand, currently feign supports only Ribbon as client side loadbalancer, which is tight to Eureka.

Since we introduced DiscoveryClient interface, which may be k8s, predefined, etc and have clean interfaces like LoadBalancerClient/ServiceInstanceChooser and ReactiveLoadBalancer,
I think it will be nice to have at least Round Robin LB based on high level DiscoveryClient.

It will allows us to choose between different discovery mechanisms (I'm currently interested in k8s discovery) and provide a basic LB support for feign.

Questions:

1. is it something already supported?
2. Is it in cloud openfeign roadmap? If yes or we are interested in it, I may try to contribute.

Thanks

[OlgaMaciaszek]

Hi @ArtyomGabeev This is a valid issue and a topic that has yet to be evaluated by the team, probably following a discussion and decisions on Ribbon replacement for the entire Spring Cloud stack (that's the issue to observe on this: spring-cloud/spring-cloud-commons#553 ). Once there's an alternative chosen/ created, we would have to provide it for our OpenFeign integration as well. If you're interested in working on this bit, we will be happy to get the contribution. Will get back to you after we've done some progress on the other issue.

[LaSylv]

Hey,

Is it something planned ?
I'd like to work on that if needed

[OlgaMaciaszek]

Hi @Glosur . yes, we've merged a PR providing our own non-reactive LB client:
spring-cloud/spring-cloud-commons#553 . One of the things I will be doing for Hoxton M3 is switching to it wherever we used Ribbon, but there's a lot of work and help is definitely welcome. Would you like to work on doing that for OpenFeign?

[LaSylv]

Thanks for the anwser @OlgaMaciaszek

I'd like to give it a try ! Any advice for this ?

[OlgaMaciaszek]

Hi @Glosur - as Hoxton is not a major release for SC OpenFeign, it's important to take into account that at this point, we need to start by adding Spring Cloud LoadBalancer to it without removing Ribbon. We have created all the necessary setup to use Spring Cloud LoadBalancer with both non-reactive and reactive setups - I guess for OpenFeign, for now, that would be the non-reactive version.

We have also created spring-cloud-starter-loadbalancer. After including it in your project, you will get a BlockingLoadBalancerClient that is in alternative to the Ribbon client; however, at this point, in order to avoid breaking backward compatibility, we use Ribbon by default. So in order to use the new client, you will have to set spring.cloud.loadbalancer.ribbon.enabled=false.

If you carry this out with a project that previously worked with Ribbon, it will start failing as at various points in Feign Ribbon Client and other Ribbon dependencies are used explicitly; now, an alternative will have to be provided - for example, by switching to using a LoadBalancerClient interface (that would get a different implementation resolved if spring.cloud.loadbalancer.ribbon.enabled=false is set) in place of Ribbon-specific implementation.

I guess there would be more questions, so for further discussion, feel free to contact me at gitter.

[OlgaMaciaszek]

Hi @Glosur - please let me know if you are going to work on it. If not, I will get it done soon.

[LaSylv]

Hello !

I started looking at the code a bit but my computer died yesterday. No problem if you get it done, I'll look at how you will do it

[OlgaMaciaszek]

Ok. Will work on it now.