#23350 closed Cleanup/optimization (fixed)
mod_wsgi authentication/authorization docs result in extra memory usage
Reported by: | Graham Dumpleton | Owned by: | Daniel Craigmile |
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Component: | Documentation | Version: | 1.6 |
Severity: | Normal | Keywords: | afraid-to-commit |
Cc: | Triage Stage: | Ready for checkin | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | yes | UI/UX: | no |
Description
The documentation at:
uses the examples:
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIPythonPath /path/to/mysite.com WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup django <Location "/secret"> AuthType Basic AuthName "Top Secret" Require valid-user AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py </Location>
and
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup django <Location "/secret"> AuthType Basic AuthName "Top Secret" AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py WSGIAuthGroupScript /path/to/mysite.com/mysite/wsgi.py Require group secret-agents Require valid-user </Location>
Although these will work, they cause the Django application code to be loaded more than once into the same process. That is, you end up with an instance in one sub interpreter which handles web request, and another instance in another sub interpreter which handles just authentication and authorisation.
Ideally you do no want two copies as that simply increases overall memory usage.
The original mod_wsgi documentation does point to this in the statements:
By default the auth providers are executed in context of first interpreter created by Python, ie., '%{GLOBAL}' and always in the Apache child processes, never in a daemon process. The interpreter can be overridden using the 'application-group' option to the script directive. The namespace for authentication groups is shared with that for application groups defined by WSGIApplicationGroup.
Because the auth provider is always run in the Apache child processes and never in the context of a mod_wsgi daemon process, if the authentication check is making use of the internals of some Python web framework, it is recommended that the application using that web framework also be run in embedded mode and the same application group. This is the case as the Python web frameworks often bring in a huge amount of code even if using only one small part of them. This will result in a lot of memory being used in the Apache child processes just to support the auth provider.
To combat this double of memory usage the mod_wsgi documentation gives the example of:
WSGIAuthUserScript /usr/local/django/mysite/apache/auth.wsgi application-group=django
It is this use of the application-group
argument for WSGIAuthUserScript
and WSGIAuthGroupScript
that the Django documentation doesn't use.
The Django examples therefore should really use:
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIPythonPath /path/to/mysite.com WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup django <Location "/secret"> AuthType Basic AuthName "Top Secret" Require valid-user AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py application-group=django </Location>
and
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup django <Location "/secret"> AuthType Basic AuthName "Top Secret" AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py application-group=django WSGIAuthGroupScript /path/to/mysite.com/mysite/wsgi.py application-group=django Require group secret-agents Require valid-user </Location>
On the presumption that there is only the one Django application, it may actually be better to turn that around and force the Django application to run in the main interpreter anyway. This is better as some third party extension modules for Python do not work properly in sub interpreters.
Thus may be better to use:
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIPythonPath /path/to/mysite.com WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup %{GLOBAL} <Location "/secret"> AuthType Basic AuthName "Top Secret" Require valid-user AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py </Location>
and
WSGIScriptAlias / /path/to/mysite.com/mysite/wsgi.py WSGIProcessGroup %{GLOBAL} WSGIApplicationGroup %{GLOBAL} <Location "/secret"> AuthType Basic AuthName "Top Secret" AuthBasicProvider wsgi WSGIAuthUserScript /path/to/mysite.com/mysite/wsgi.py WSGIAuthGroupScript /path/to/mysite.com/mysite/wsgi.py Require group secret-agents Require valid-user </Location>
Change History (9)
comment:1 by , 10 years ago
Component: | Uncategorized → Documentation |
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Triage Stage: | Unreviewed → Accepted |
Type: | Uncategorized → Cleanup/optimization |
comment:2 by , 10 years ago
Easy pickings: | set |
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Keywords: | afraid-to-commit added |
I've marked this ticket as especially suitable for people following the Don't be afraid to commit tutorial at the DjangoCon US 2014 sprints. If you're tackling this ticket, please don't hesitate to ask me for guidance if you'd like any, either at the sprints themselves, or here or on the Django IRC channels, where I can be found as EvilDMP.
comment:3 by , 10 years ago
Owner: | changed from | to
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Status: | new → assigned |
comment:4 by , 10 years ago
I made the changes listed above here: https://github.com/django/django/pull/3176
comment:5 by , 10 years ago
Has patch: | set |
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Triage Stage: | Accepted → Ready for checkin |
GrahamDumpleton approves the change, though doesn't address aaugustin's concerns.
comment:6 by , 10 years ago
I am not an expert, but reading through the ticket, it seems like a warning to the effect of "The use of WSGIApplicationGroup %{GLOBAL}
presumes that your Apache instance is running only one Django application. If you are running more than Django application, please refer to the mod_wsgi docs for more information about this setting."
comment:7 by , 10 years ago
Resolution: | → fixed |
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Status: | assigned → closed |
I believe we should provide a copy-paste-proof example for the simple case of "first time I'm touching Django and Apache, how do I run my test project?" and shell out to mod_wsgi's own docs for anything more complicated.
For that use case, we can assume that there's only one Django application.
We just need: