A common configuration I’ve seen for nginx + tornado is to have nginx serve static files and then act as a reverse proxy to some upstream tornado app servers. I know this configuration is often used to serve an application through wsgi (such as Django) which blocks tornado. In that case the usual approach is to run as many tornado processes as will fit in memory and then have the nginx front round robin across processes.
If I were to use a CDN instead of nginx to serve static files and run tornado in a non-blocking fashion, is there any advantage to running more total processes (i.e. 1 nginx and 1 tornado per core) than there are cores on the machine?
If the Tornado instances have no blocking code, there is not much to gain from running more Tornado instances than the number of CPU cores. With blocking code (like using blocking libraries or db drivers inside IOLoop), it’s advised to run more instances than cores to utilize CPU resources better (2-3 per core).