I’m using HAProxy to load balancing gRPC backends. Sometimes I need to temporarily remove a backend from backends list in the config file to upgrade it, then I re-add it to the list later. I’m curious what will happen to ongoing requests of the removed backend? Does HAProxy immediately close these requests when I reload the config?
When you reload, connections are not interrupted at all, they keep going on until the close naturally or due to the hard-stop-after timeout.
When you restart haproxy, all connections are dropped immediately.
Whether the server has been removed from the configuration or not is irrelevant. The new configuration is relevant only for new connections.