Implement Retryable feature of spring cloud LoadBalancer for ReactiveLoadBalancerClientFilter

Currently, the ReactiveLoadBalancerClientFilter, which implements load balancer usage, does not take into account the retry features specific to the load balancer (e.g., the use of maxRetriesOnNextServiceInstance).

It appears that the ReactiveLoadBalancerClientFilter is primarily based on the functionality of the ReactorLoadBalancerExchangeFilterFunction (from spring-cloud-commons), but there is no implementation that incorporates the features of the RetryableLoadBalancerExchangeFilterFunction.

In my case, the use of Spring Cloud Gateway Retry does not necessarily target a different instance than the first one that failed (it depends on concurrency).

Sample with load balancer with 2 instances (I1 - DOWN and I2 - UP)

Successful case
Request 1 => LB choose I1 => FAILED
Retry Request 1 => LB choose I2 => OK

Failed case
Request 1 => LB choose I1 => FAILED
Request 2 (concurrency call) => LB choose I2 => OK
Retry Request 1 => LB choose I1 again => FAILED

Thank you for your help.

spring-cloud-gateway
ReactiveLoadBalancerClientFilter.java

spring-cloud-commons
ReactorLoadBalancerExchangeFilterFunction.java
RetryableLoadBalancerExchangeFilterFunction.java

Start with spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/ReactiveLoadBalancerClientFilter.java and compare it with the linked ReactorLoadBalancerExchangeFilterFunction and RetryableLoadBalancerExchangeFilterFunction in spring-cloud-commons. Trace how retryable load-balancer settings such as maxRetriesOnNextServiceInstance should affect instance selection, then verify the two-instance failure and retry scenarios described in the issue.