id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26293	Warnings regarding 404s logged for URLs missing trailing slashes	JK Laiho	Sam	"I recently deployed a project into production using Django 1.9.2 and started getting strange logged warning messages from Sentry for 404's. Looking into it, this occurred in `django.core.handers.base.BaseHandler.get_response` and was related to people visiting URLs without trailing slashes.

I compared the behaviour against an earlier, similarly configured project still running Django 1.7.x and this didn't occur there.

Digging deeper, it seems that commit [https://github.com/django/django/commit/434d309ef6dbecbfd2b322d3a1da78aa5cb05fa8#diff-1f8be0eae49a1bf37d52829eaeda6a4e 434d309e] to fix [ticket:24720] inside `CommonMiddleware` was causing this. In lines 56-66 (58-68 in 1.9.2), the path is only checked for a missing slash if the prerequisites for `PREPEND_WWW` processing are met, since they are indented beneath it. This doesn't really make sense, since the two settings are not interdependent.

As a result, an `Http404` is raised after request middleware processing in `BaseHandler.get_response`, at which point a warning is logged—for every single request for a path without a trailing slash.

`APPEND_SLASH` still takes effect eventually, but only when `CommonMiddleware` is called again, this time for `process_response`, whereupon the normal redirect gets done. Thanks to this, everything appears to function normally for the end user, but unnecessary 404 warnings end up getting logged. (Though if `APPEND_SLASH` was `False`, you'd probably want them logged.)

It seems to me that `CommonMiddleware.process_request` needs a bit of reworking to run the checks for `PREPEND_WWW` and `APPEND_SLASH` independently, and to determine the need for a redirect based on whether at least one of these is necessary, still fulfilling the purpose of [ticket:24720]. I've provisionally marked the ticket as ""easy pickings"", as it seems to be that way from my admittedly limited research into this."	Bug	closed	HTTP handling	1.9	Normal	fixed	CommonMiddleware 404 logging regression	Emett Speer	Accepted	1	0	0	0	1	0