Add load balancing mechanism Peak EWMA for Spring-cloud-gateway for Kubernetes

[nightguide]

Describe the solution you'd like It would be great if Spring-cloud-gateway for Kubernetes supported the Peak EWMA (peak exponentially-weighted moving average) load balancing mechanism.

You can read about what Peak EWMA is here:

• Beyond Round Robin: Load Balancing for Latency
• Kubernetes on a High Traffic Environment: 3 Key Takeaways

It would be great if spring-cloud-gateway for Kubernetes could track the response time of endpoints in Kubernetes services and could balance based on EWMA. This is very useful when the application is under high load.

Describe alternatives you've considered

• As an alternative, we can use Peak EWMA balancing on the Kubernetes Ingress Controller, but then we need to pass all internal traffic in Kubernetes through it. This heavily loads the network bandwidth. And actually it's not a very good practice. Since ingress controller is used to balance internal Kubernetes traffic, not external.

load balance Ewma on Kubernetes Ingress Controller

• Another alternative is to use the service mesh for example Linkerd. But the mesh service always adds resource overhead and complicates the management between service networking. From the functionality of the service mesh, we only need the EWMA balancing mechanism.

• Use different API Gateway for example [Apache APISIX]https://apisix.apache.org/docs/ingress-controller/concepts/apisix_upstream/l)

Additional context

[spencergibb]

This scala will be easier to read than the lua https://github.com/twitter/finagle/blob/develop/finagle-core/src/main/scala/com/twitter/finagle/loadbalancer/PeakEwma.scala

@OlgaMaciaszek does this belong in spring-cloud-gateway?