Default Design

By default, NGINX server has the following design:

• A multi-threaded process creates N threads.
• Each thread creates an epoll object.
• Each thread creates a listen socket that uses SO_​REUSEPORT.
• Each thread calls an accept connection syscall and waits to be woken up to handle an incoming connection.
• The kernel assigns the accepted connection to a thread's epoll object via JHASH-based selection. This is calculated using src IP + dest IP + src port + dest port.
• Each thread processes an epoll object:
  • Performs epoll_​wait.
  • When epoll_​wait returns from syscall, the thread performs read/recv/write/send on sockets