Bug 654 - MapDHTMLwidget occassionally fails
: MapDHTMLwidget occassionally fails
Status: RESOLVED WONTFIX
: Chameleon
Widget
: 1.99
: PC Windows XP
: P2 critical
: FUTURE
Assigned To:
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Reported: 2004-08-30 03:00 by
Modified: 2006-01-23 04:10 (History)


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Description From 2004-08-30 03:00:21
Occassionally the map in Chameleon displays a red cross in IE. Several users on
the user list have encountered this problem. Also, scalebars etc. sometimes
fail. This even happens on fast ADSL or in-house servers in my case.

I have tried to reproduce this problem using 1) a Python script and 2) a really
simple HTML page. The Python script loads a drawmap.phtml URL 50 times and none
of them fail. Only apparant thing is that the first load is always 4 seconds
instead of around 1,3 seconds.

The HTML page is really simple and reproduces the problem in my situation:

<html>
<script>
function load()
{
  document.images["bart"].src=
"/chameleon//common//wrapper/drawmap.php?map_session_mode=1&run_query=0&sid=4132c68f4bf7b&dummy=0.67554800+1093846677";
}
</script>
<body onload="load()">
<img id="bart">
</html>

The test page is situated here:
http://www.vz.geodan.nl:1111/test.html
------- Comment #1 From 2004-08-30 03:07:57 -------
Just found out this is Internet Explorer only. Mozilla Firefox never fails this
test script.
------- Comment #2 From 2004-08-30 03:32:45 -------
I have also had it happen to me in firefox, but way less often (hardly
reproduceable). I notice it is more prone to happen when the site is viewed from
a machine other than the server itself. It does not only affect the mapimage for
me, but also buttons, legend images, and scalebar (especially on first load).
Even through a dial-up connection.
For me, it only happens when there is an image in the background (TIFF and ECW,
possibly others). It happens more quickly if the JPEG quality is higher. Both
1.0.4 and 1.99 have this problem. However, I have no seen this happen in IIS,
only apache.
Jacob
------- Comment #3 From 2004-08-30 03:44:00 -------
Even putting the URL directly into the browser and reloading the browser page
reproduces the problem.
------- Comment #4 From 2004-09-03 13:54:46 -------
Changed Target to 1.99 RC 1.
------- Comment #5 From 2004-09-19 21:47:43 -------
Have still been experiencing this problem, especially with dial-up. Also
non-chameleon images break, which makes me very sure it's apache, not chameleon.
Ran into this piece of documentation, which I think may be related. I do not yet
know whether it works, since the problem is hard to reproduce when you want it
to occur (Maybe Bart can reproduce it at will?).

http://www.apache.org/dist/httpd/binaries/win32/#problems

It basically tells to put these lines into httpd.conf:
#------------------------------
EnableSendfile Off
EnableMMAP Off
Win32DisableAcceptEx
#------------------------------

If this doesn't help, it may have to do with the maximum of 10 users that is
allowed to be connected to a workstation (windows non-server). I think that only
applies to IIS, though.

Jacob
------- Comment #6 From 2004-09-19 23:47:00 -------
BTW, that suggestion about those three lines does require apache 2.0.50, I
think. It's probably the last two lines that need the new version, though based
on some sites I think it's the first line that is most likely to fix the issue
(EnableSendfile Off). So if you run an older version, try only that line.
------- Comment #7 From 2004-10-04 23:36:12 -------
Have just migrated to a new server. Exact same hardware specs (except 1GB of RAM
instead of 512MB, but that shouldn't matter). However, this one runs Windows
2003 server. Unfortunately.... it didn't fix the problem.

I did find out that it is something to do with internet explorer 6. I have
tested this through dial-up, and the problem always occurred in IE6. On the same
machine, but booted in win2k with IE 5.5, it did not occur. It seems that IE5.5
loads things one by one, without a problem, but that IE6 tries to get more than
1 image at once. Is there a limit to how many PHP requests a server allows at once?
------- Comment #8 From 2004-11-03 15:09:10 -------
not AFAIK.  I've never been able to reproduce this so it isn't likely to get
fixed in 1.99 but I'll leave it open for FUTURE in case we find out something
about it ...
------- Comment #9 From 2006-01-23 04:10:36 -------
A few tips/solutions have been posted for this. One of them is to check the
Windows registry (e-mail from Jacob Delfos in January 2006), and another one
suggested to put KeepSessionAlive to false in the Apache conf file.

Marking this bug as WONTFIX as apparently it has nothing to do with the
Chameleon core.