Query a pool according to the hostname without opening the encryption

adding to Amine_Kadimi ,

most clients send intended server hostname during SSL session setup, so that SSL server can response with proper server's certificate.
this method allows same server serves mutiple SSL hostnames using different certificate for each hostname.
the sample config above actually reads that hostname.

you can read more about TLS SNI here:
https://www.cloudflare.com/learning/ssl/what-is-sni/