#26293: Warnings regarding 404s logged for URLs missing trailing slashes
-------------------------+-------------------------------------------------
Reporter: jklaiho | Owner: nobody
Type: Bug | Status: new
Component: HTTP | Version: 1.9
handling | Keywords: CommonMiddleware 404 logging
Severity: Normal | regression
Triage Stage: | Has patch: 0
Unreviewed |
Easy pickings: 1 | UI/UX: 0
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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.
--
Ticket URL: <https://code.djangoproject.com/ticket/26293>
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