Multi-tenancy support

Hi all, I have been working on a project that we need to support more than 10000 tenants. I tried to create multiple virtual servers and each listen to different ports and I found that I can only create up to 300 virtual servers due to the limitation of FD_SETSIZE. In this case I will need to have more than 300 servers running which doesn't seem to make much sense. I also consider the option of creating multiple client sections to specify the source IP addresses and the corresponding virtual server. However, I don't seem to find a way to identify tenants if the incoming traffic is from the same proxy server. I am running out of options and hoping that you may share your experience or suggestions. thank you very much Cecil