532416 - Broken disk cache

Status: RESOLVED DUPLICATE of bug 487457

(Core :: Networking: Cache, defect)

Description

[Timur Amirov]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.0.04506.30)
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5 (.NET CLR 3.0.04506.30)

After some time of using map (that means loading quite a number of tiles) the cache spoils. It looks like this:
1.Page wants to show a picture.
2.Browser counts this picture to be in cache and gets it from there. 
3.Wierdly, there is no such picture and error code 404 is returned. Server is
not requested.
3.Page shows special picture for error (screenshot).
4.To make things worse, the answer is remembered. So, after bad tile appears,
it will be there for intolerable amount of time.

Screen:
http://img-fotki.yandex.ru/get/3806/maps-testerbot.0/0_1927e_dc3c4215_orig

The bug can be reproduced in ff 2,3,3.5 in winXP, ubuntu, Mac. Actually, we've
seen it everywhere we have recurrent testing activity.

In some other cases cache returns wrong pictures (which were actually taken from another url). Screens:
http://img-fotki.yandex.ru/get/3906/maps-testerbot.0/0_19c38_b3917f8b_orig
http://img-fotki.yandex.ru/get/4000/maps-testerbot.0/0_19c39_83e23b37_orig
http://img-fotki.yandex.ru/get/3804/maps-testerbot.0/0_19c3a_f2d4be2e_orig

Reproducible: Sometimes

Steps to Reproduce:
0. clear cache
1.Browse maps for some time.

u need to load many pictures. so we are talking about quite a long period of time. That's why we stated reproducibility not always. But sooner or later, it happens.
Actual Results:  
Wrong picture or 404 error will start return from cache instead of map tiles

Comment 1

[Timur Amirov]

We belive the problem can be simulated. Details below.

We have taken some files from cache right after the incident. Dirty flag is false, but _CAHCE_MAP_ has entries for files that are actually missing.
Cache and log for it can be downloaded as an archive from here:
http://narod.ru/disk/14994671000/reportandlog.zip.html
(enter protecting digits into text field and push green button "Скачать")

After turning on https://developer.mozilla.org/en/HTTP_Logging
Checked log for file existing in cache. Manually deleted file and asked for it
again. In both cases (file exists/is missing in cahce directory):
nsHttpChannel::ReadFromCache [this=...] Using cached copy of: ...

Proposed solutions:
1.Find and fix error of wierdly dissappearing files.
2.Check file existance when we are trying to get it from cache. If it's gone -
delete reference from cache map.

This issue may appear to be relevant to:
https://bugzilla.mozilla.org/show_bug.cgi?id=175600
https://bugzilla.mozilla.org/show_bug.cgi?id=263590
https://bugzilla.mozilla.org/show_bug.cgi?id=105843#c73 (using SQLite for cache
improvement)

Thanks for your investigation of the problem.