“NGINX release 1.9.1 introduces a new feature that enables use of the SO_REUSEPORT socket option, which is available in newer versions of many operating systems, including DragonFly BSD and Linux (kernel version 3.9 and later). This option allows multiple sockets to listen on the same IP address and port combination. The kernel then load balances incoming connections across the sockets, effectively sharding the socket.
(For NGINX Plus customers, this feature will be available in Release 7, which is scheduled for later this year.)
The SO_REUSEPORT socket option has many real-world applications, such as the potential for easy rolling upgrades of services. For NGINX, it improves performance by more evenly distributing connections across workers…”