Thanks for the reply.
I tried the loadbalancing with nginx for the 2 frontend running on 2 VMs. I did not use downstream_url but the frontend_worker since there is a discussion in another topic that this way could bring some more parallesium.
However, the configuration is not that simple as expected. As you know that the fronend_worker shoud point to the grpc port of the frontend, then how about the port 3100 for http queries?
I posted this out in another topic https://community.grafana.com/t/how-to-configure-nginx-for-frontend-worker/52306, your suggestion is highly welcomed.
Btw, I set a memberlist for ingesters and distributors and configure the nginx for them as well, that looks fine for now.