I have a webserver with 3 WSGI applications running on different domains (1, 2, 3). All deployed with a combination of Gunicorn and NGINX. A combination that works really well, but there are two annoyances that are only going to get worse the more sites I deploy:
A) The configuration for each server resides in a different location on the filesystem, so I have to recall & type a long path to edit settings.
B) More significantly, each server adds extra resource requirements. I follow the advice of running each WSGI application with (2 * number_of_cores + 1) processes, each with 8 threads. The threads may be overkill, but that ensures that the server can use all available capacity to handle dynamic requests. On my 4 core server, that's 9 processes, 72 threads per site. Or 27 processes, and 216 threads for the 3 sites. Clearly that's not scalable if I want to host more web applications on one server.
A new feature recently added to Moya fixes both those problems. Rather than deploy a WSGI application for each site, Moya can now optionally create a single WSGI application that serves many sites. With this new system, configuration is read from /etc/moya/, which contains a directory structure like this:
| |-- moyapi.ini
| |-- moyaproject.ini
| `-- notes.ini
At the top level is “moya.conf” which contains a few server-wide settings, and “logging.ini” which contains logging settings. The directories “sites-available” and “sites-enabled” work like Apache and NGINX servers; settings for each site are read from “sites-enabled”, which contains symlinks to files in “sites-available”.
Gunicorn (or any other wsgi server) can run these sites with a single instance by specifying the WSGI module as “moya.service:application”. This application object loads the sites from “sites-available” and is responsible for dispatching requests based on domains specified in the INI files.
Because all sites now go through a single Gunicorn instance, requests are shared amongst one optimal pool of processes / threads. This keeps the memory footprint low and negates the need to allocate resources based on traffic.
This new multi-server system is somewhat experimental, and hasn't been documented. But since I believe in eating my own dog-food, it has been live now for a whole hour–with no problems.