569310 - [k] Entire forum deleted accidentally (related to DoesNotExist: Post matching query does not exist assertion?)

Status: VERIFIED FIXED

(support.mozilla.org :: Forum, task)

Description

[Stephen Donner [:stephend] Not actively reading bugmail]

Finally, I have a screencast capture of the "delete sometimes deletes entire forums (!)" bug.

Sadly, I don't have concise STR, but we'll have to work backwards from it.

It goes without saying that bug 568636 would help here, too.

SCREENCAST: http://screencast.com/t/ZDhiNWQzNDUt

Traceback (most recent call last):

  File "/data/virtualenvs/kitsune/src/django/django/core/handlers/base.py", line 101, in get_response
    response = callback(request, *callback_args, **callback_kwargs)

  File "/data/virtualenvs/kitsune/src/django/django/contrib/auth/decorators.py", line 24, in _wrapped_view
    return view_func(request, *args, **kwargs)

  File "/data/virtualenvs/kitsune/src/django-authority/authority/decorators.py", line 54, in decorated
    return view_func(request, *args, **kwargs)

  File "/data/www/support-stage-new.mozilla.com/kitsune/apps/forums/views.py", line 245, in delete_post
    post.delete()

  File "/data/www/support-stage-new.mozilla.com/kitsune/apps/forums/models.py", line 128, in delete
    if forum.last_post and forum.last_post.id == self.id:

  File "/data/virtualenvs/kitsune/src/django/django/db/models/fields/related.py", line 276, in __get__
    rel_obj = rel_mgr.using(db).get(**params)

  File "/data/virtualenvs/kitsune/src/django/django/db/models/query.py", line 339, in get
    % self.model._meta.object_name)

DoesNotExist: Post matching query does not exist.



Semi-STR:

1. Create a bunch of posts (I think having more than one pages is necessary)
2. Reply to a couple posts
3. Delete, delete, delete (start with the posts above the replies, and if that doesn't work, try the replies themselves)

Again, random, so hard to reproduce.  But I've done this twice now, which is indeed scary.

The following assertion seems to be relevant; our count might be going off into the weeds:

Traceback (most recent call last):

  File "/data/virtualenvs/kitsune/src/django/django/core/handlers/base.py", line 101, in get_response
    response = callback(request, *callback_args, **callback_kwargs)

  File "/data/virtualenvs/kitsune/src/django/django/contrib/auth/decorators.py", line 24, in _wrapped_view
    return view_func(request, *args, **kwargs)

  File "/data/virtualenvs/kitsune/src/django-authority/authority/decorators.py", line 54, in decorated
    return view_func(request, *args, **kwargs)

  File "/data/www/support-stage-new.mozilla.com/kitsune/apps/forums/views.py", line 245, in delete_post
    post.delete()

  File "/data/www/support-stage-new.mozilla.com/kitsune/apps/forums/models.py", line 128, in delete
    if forum.last_post and forum.last_post.id == self.id:

  File "/data/virtualenvs/kitsune/src/django/django/db/models/fields/related.py", line 276, in __get__
    rel_obj = rel_mgr.using(db).get(**params)

  File "/data/virtualenvs/kitsune/src/django/django/db/models/query.py", line 339, in get
    % self.model._meta.object_name)

DoesNotExist: Post matching query does not exist.

Comment 1

[Stephen Donner [:stephend] Not actively reading bugmail]

Eh, sorry about the epic double-paste, there.  C&P FTL sometimes, especially when it's below-the-fold.

Comment 2

[James Socol [:jsocol, :james]]

We do log deletions: we just need to double check to see where they're going.

Comment 3

[Ricky Rosario [:rrosario, :r1cky]]

STR:

1) Go to the last post of the forum
2) Add a new reply
3) Delete the second to last post (what used to be the last post)

BAM!

Looks like a caching issue.

Comment 4

[James Socol [:jsocol, :james]]

Step 0: flush cache to start with a clean slate.

Comment 5

[Ricky Rosario [:rrosario, :r1cky]]

http://github.com/rlr/kitsune/compare/7f8b30e481...f1fdaa4c50

Comment 6

[Stephen Donner [:stephend] Not actively reading bugmail]

Verified FIXED; I'll write a Litmus test for this later, and I'm roping in Tanay to write an automated one in Selenium/Python :-)

Comment 7

[Tanay Gavankar [:tgavankar]]

Selenium python test script is up (called forum_deletion), see bug 569655

Comment 8

[Rebecca Billings [:rbillings]]

Added to Litmus - testcase #11886