The request_started signal is not called for the first request a newly-initialized webserver receives.
|Reported by:||etianen||Owned by:||nobody|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
When running Django on Apache and mod_wsgi via the WSGIHandler, the request_started signal is not sent on the first request. This problem potentially affects other server handlers too.
This problem occurs because on the first request to the server, the following sequence of actions occurs:
- request_started signal called
- Application modules are loaded, code containing signal connections is run.
- Request is handled
- request_finished signal is called
On the second request, because the application code which contains the signal handlers has been run, and the signal connections established, everything behaves has expected.
A consequence of this is that code which is expecting matched pairs of request_started and request_finished invocations for the current thread will perform unpredictably on the first request handled by the server. Subsequent requests will behave as expected. Even code that only connects to request_started will behave oddly on the first request.
The solution might be to have a module in each application which is guaranteed to be loaded before the request_started signal is called. Something like app_label/signals.py. The BaseHandler would be modified to have a load_signals() method that would iterate over the installed apps and import the signals module if present. Handler subclasses would then call this load_signals() method before the first request is handled, in a similar way to the current handling of the load_middleware() method.
Change History (6)
comment:1 Changed 4 years ago by etianen
- Cc etianen added
- Needs documentation unset
- Needs tests unset
- Patch needs improvement unset
comment:3 Changed 4 years ago by aaugustin
- Component changed from Core (Other) to Documentation
- Triage Stage changed from Unreviewed to Accepted