80922 - Dynamic image not reloading even though retrieved from the server.

Status: RESOLVED WORKSFORME

(Core :: Networking: HTTP, defect, P3)

Description

[tenthumbs]

There may be an interaction with imagelib but I'm reasonably sure this 
is a network problem of some kind. I'm nor sure, though, whether this is 
just a cache issue or whether more is involved. Feel free to reassign it.

I have a simple CGI test script that returns a random JPEG image. It's 
size is changing all the time. Depending on how it's called, there may 
be a content-length, or a last-modified, an expires header, or any 
combination of these headers. For this bug, we will consider the case 
where it returns a content-length and a last-modified header which is 
what a static image would return. Because the image is dynamic, the 
last-modified time is always 30 seconds before the access time.

On an initial load, mozilla has no trouble displaying the image. On a 
reload, mozilla grinds away for a while but nothing changes. On a 
shift-reload, mozilla grinds away even longer but does display a new 
image.

The server logs show something far more interesting. A reload initiates
a network connection, data is actually transferred, but mozilla throws
it away. In mozilla's cache, the disk object for the initial image just
disappears. A shift reload shows mozilla making _two_ apparently
consecutive connections. Data is transferred on both but mozilla only
uses the last one.

As far as the headers form the server are concerned, the only difference 
is a ETag header. The script does not return one. All other headers have 
the same form, although different contents obviously.

Using, or not using, a proxy server also makes no difference.

The only anomaly I can find is in mozilla's disk cache. If you look at 
the attached html file from about:cache, you'll see the mozilla expires 
it metadata 2 seconds before its last modified time. Odd.

I tested with an 0514 build but it's been happening for a wile now.

Comment 1

[tenthumbs]

Attachment: about:cache entry

Comment 2

[neeti]

Reporter: could you provide a testcase for this?

Comment 3

[tenthumbs]

A test case is hard because it's a cgi script and the server is not easily
available. I'll attach the script itself. If you've got Linux and Apache you can
just drop it into Apache's cgi-bin directory and make it executable.

Comment 4

[tenthumbs]

Attachment: random image perl script

Comment 5

[neeti]

tever : could you test this script out?

Comment 6

[neeti]

-->cache

Comment 7

[gordon]

Neeti, why do you think this is the cache?  Isn't this more likely to be an HTTP 
issue?

Comment 8

[Tom Everingham]

Neeti, this is set up internally at http://backwash/cgi-bin/random.jpg if you 
want to test it.  I haven't looked into any details yet but it doesn't seem to 
work correctly on 6.x.  I'll look into it a bit more tomorrow.

Comment 9

[neeti]

Reporter: this is working for me on a linux build pulled on 5/21. Could you try 
this again with thge latest builds.

cc'ing pavlov

Comment 10

[tenthumbs]

In a 05-22-13 nightly it's not fixed although the behavior is different.
Now both reload and shift-reload hit the server twice. The first reload
throws an error message to the xterm. I suspect that makes mozilla
retrieve it again.

It looks like its working but it's not.

Comment 11

[Luud Heck]

*** Bug 82330 has been marked as a duplicate of this bug. ***

Comment 12

[benc]

UPDATE: Mozilla 0.9.1, Win98 (commercial)

I've used the backwash URL, and it seems to work correctly to me, but I do not
have admin access to the server, so I can't speak to the lower level issues.

I think we need traction on deciding which component owns this bug.

Comment 13

[Doug Turner (:dougt)]

pav, this is you.

Comment 14

[Stuart Parmenter]

someone should retest this with a recent build.

Comment 15

[tenthumbs]

Stiil there in an 07-10-21 nightly but the behavior is slightly
different. On a reload, mozilla retrieves a new image, stores it in the
disk cache, displays it, but then retrieves yet another image but
apparently throws it away.

That's for viewing an image directly in mozilla. This does *not* happen
if a dynamic image is embedded (via a <img> tag) in a dynamic html
document. In this case, there is only one fetch for each.

Comment 16

[[not reading bugmail]]

is this url what your seeing?  testing this in build 2002-2-8-03 w2k.

http://www.shacknews.com/screens.x/quake3/Urban+Terror/1/ut24/beta24_shot01.jpg

Comment 17

[Robin Monks]

*** Bug 285232 has been marked as a duplicate of this bug. ***

Comment 18

[Ioana (away)]

Is this still an issue? None of the links in comments are valid (useful for testing) anymore.

Comment 19

[Patrick McManus [:mcmanus]]

there is a shell script attached which purports to demonstrate the problem. Can't QA check that?

Comment 20

[Ioana (away)]

I tested with the script and the doesn't reproduce on Mozilla/5.0 (X11; Linux i686; rv:25.0) Gecko/20130728 Firefox/25.0.

At each reload (however it's done), an image gets retrieved very fast.

Please only reopen this bug if you can reproduce it.