[question] least connections GRPC load balancing

[vrnmthr]

I understand that we can create a custom load balancer as per https://learn.microsoft.com/en-us/aspnet/core/grpc/loadbalancing?view=aspnetcore-5.0#create-a-custom-load-balancer.

I want to create a load balancer that sends requests to the endpoint with the least number of currently active connections. With the SubchannelsLoadBalancer, I can always know when I am "picking" a given subchannel (and thus I can increment its connection count). Is there any hook that I can call when a given request is completed (so I can decrement connection count)?

I am sure that this type of load balancing will be useful for many people. Perhaps it is worth adding into the library as an out of the box configurable option.

[vrnmthr]

I found https://github.com/grpc/grpc-dotnet/blob/master/test/FunctionalTests/Balancer/LeastUsedBalancer.cs. @JamesNK is there a reason this is not exposed publicly?

[JamesNK]

Because it was just an experiment. It also isn't perfect. It doesn't properly track long running streams. It only tracks calls until they return the first message.

[AntonSmolkov]

@JamesNK Are there any plans to make public implementation?

It would be helpful, for instance, in kubenetes envinronment when cpu requests != limits (QoS=Burstable) to distribute load according to real resouses avalability of each pod in the k8s deployment. With round-robin strategy pod that actually has lower resources handles requests slower and thus has more connections stick to it in particular moment of time.

[JamesNK]

No plans.