[IgorPartola]

I am not familiar with how .NET does this. Perhaps it has some kind of a mechanism for dealing with this. Here is an example from the Django/Python world. In your virtual host apache config you have to specify the following:

  WSGIDaemonProcess myapp processes=5 threads=5 display-name=myapp-name user=myappuser
  WSGIScriptAlias / /var/www/vhosts/example.com/apache/myapp.wsgi
  WSGIProcessGroup myapp

Notice the process=5 threads=5. This means that apache will run 5 processes, with 5 threads each. Now imagine if you have several of these apps, all configured to use 5 processes and 5 threads each, which eats up 80% of the RAM on your server. Now, app A gets featured on HN, and lots of requests come in to that app. You can only process 25 concurrent requests (and really fewer since Python's GIL prevents CPU-intensive load to be efficiently scheduled between the 5 threads per process). However, while app A is getting slammed, apps B, C, D, and E are idle. You could get more performance for app A by reducing the number of processes/threads for apps B-E and increasing the number of processes/threads for app A, but this means manually doing so and reloading apache. Less than ideal.

Edit: obviously, don't use this config example.

[papsosouid]

Your example is not a problem with using an efficient execution model, it is a problem with django/wsgi. In fact, your example is using the exact same model as apache, it just sucks at it and makes you statically define the number of workers on a per app basis. You can easily have multiple web apps running in a single application server, and the resource limits will be shared just like with a typical apache+php setup.

Note that in environments where this sort of thing is trivial to do (java for example), virtually nobody does it, preferring to run separate servers per application anyways.

[IgorPartola]

The way I understand it is that you either have a pool of interpreters per app or per set of apps. In the second case, life is easy: you can have a simple system that allocates interpreters to apps on demand. In the first case, you have to have a more complex solution. Perhaps the process manage (in this case apache) could implement such a system, but thus far it has not.

[papsosouid]

There's no need for sets of interpreters at all, that's what I am saying. Python being worse at this than PHP doesn't mean PHP is good at it. Look at go for example, there's one app server, running as many apps as you want.