Executing different uwsgi binaries per-vassal

[akx]

I bumped into an issue like this the other day:

• A system-wide uWSGI is acting as emperor-tyrant, with a number of vassals
• Vassal uWSGIs may require different versions of Python (from Pythonbrew, for instance) and of course are thus compiled against different libpythons (non-plugin builds)

However of course the emperor will run only itself, or whatever is set as binary-path in its configuration. The binary-patch options won't work, because uWSGI will then enter an infinite restarting loop as it detects the same binary-patch option over and over.

So, I propose binary-path could also be set in vassal configuration, wherein it has an immediate effect:

• If the emperor fd is detected and the currently executing binary isn't the one set as binary-path, exec binary-path.

This would effectively make it possible for the just-starting uWSGI vassal to switch to the correct uWSGI binary.

Thoughts?

[prymitive]

Can't you compile python support as plugins for each python version and load the right one in each vassal? That's the most common way.

[unbit]

probably i would suggest the plugin approach too (with the new build system is really easy to build ad-hoc plugins as for example in uwsgi.it rvm support: https://github.com/unbit/uwsgi.it/blob/master/snippets/rvm.md#using-rvm).

Eventually give a look at the --emperor-wrapper option that will override the binary used by the Emperor for vassals. You can create an ad-hoc script for exec'ing the right binary (no idea on how to instruct it about the python version, but there are solution for sure)

[unbit]

in 2.1 we have introduced vassal's attributes. You can now have this kind of configuration:

[emperor]
mywrapper = /usr/local/bin/uwsgi_python34

[uwsgi]
http-socket = :9090
...

uwsgi --emperor /etc/uwsgi/vassals --emperor-collect-attr mywrapper --emperor-wrapper-attr mywrapper