[ic] mod_interchange and Apache MaxClients

John1 list_subscriber at yahoo.co.uk
Wed Dec 21 18:37:52 EST 2005

On Wednesday, December 21, 2005 5:03 PM, rphipps at reliant-solutions.com 

>> From: Ron Phipps
>> Sent: Tuesday, December 20, 2005 2:07 PM
> <snip>
>> Are you using a script to restart your site or do you restart it by
>> hand?  If you restart it by hand could you please setup a cgi test
>> domain and hit that site before you restart IC/Apache?
I am using *your* script (1 minute cron job) to restart Apache and 
Interchange whenever it fails to respond.

So it sounds like from the work you have done with a cgi test domain that 
Interchange fails to respond via tlink aswell.

BTW, I feel a bit bad that the subject of this thread is 
"mod_interchange..." when it may or may not be anything to do with 
mod_interchange - sorry Kevin :-o.  I would post my reply with a new subject 
but that seems bad form now the thread is underway...should we change the 
subject of postings to this thread?

>> Something in these worms is causing mod_interchange or IC to hang,
>> but I'm not sure I know where to look from here.  It'd be great if
>> there was a script that recreated the actions of these worms, but I
>> have not found one yet.  If we could recreate the problem on demand
>> then it'd be much easier to find a fix.  Unfortunately right now we
>> have to make a change then wait for the worm to attack again.
I have created a little perl script to try to emulate the awstats GET and 
xmlrpc POST requests but Interchange seems to cope fine with my script, 
returning status 200 (and no doubt returning the interchange missing.html 
page, although I haven't bothered checking the contents of the request 
response in the script).  So I am still at a loss as to exactly what is 
causing IC to hang.

The only thing I am 100% sure about is that this worm (i..e variants of the 
Lupper worm) are definitely the culprit - each time, and very shortly before 
IC hangs I can always see in the log the following three GET requests:


      or on a couple of occasions, the following 2 GET requests


More detail in previous post to this thread:

>> Does anyone know of any communities where they would post such a
>> script?
There is an analysis of the packets sent (by one of the Lupper variants) at:

It should be possible to reconstruct the GET and POST requests from this 
data, but unfortunately this page is unavailable at the moment - "The server 
is temporarily unable to service your request due to the site owner reaching 
his/her bandwidth limit. Please try again later."

Snip from earlier post to this thread by Kevin:
>Thanks for posting the packet data.  I'll use that to try to recreate
>the problem locally.  I imagine I'll have to throttle the link and/or
>fire truck-loads of simultaneous requests to get the problem to show
>itself.  If the problem can be recreated on demand then it can be found
>and fixed.  I have an old P200 that I use for performance tests.  Test
>time differences are amplified massively when running Interchange on a
>P200 with 128MB of memory. :-)
Kevin, did you get chance to do this?

>> I think what I'm going to do next is add those xmlrpc paths to either
>> the ordinaryfilelist or the dropfilelist of mod_interchange so that
>> the posts are not passed along to IC.
> The DropRequestList looks like this now in the interchange-handler
> section:
> DropRequestList /default.ida /x.ida /cmd.exe /root.exe /xmlrpc.php
> Since I implemented this, the site has been hit by the worm 6 times,
> but my script has not detected the site going down.
OK, I have just updated our DropRequestList to include /xmlrpc.php.  So, if 
this has stopped your site falling over it does look like it is the contents 
(or frequency) of xmlrpc.php POST requests that are causing the problem.  I 
will let you know if our site also now stays up.

We have seen a similar pattern to you Ron - site didn't go down at all 
between 8 December and 16 December (during which time the site was very 
busy).  However, since 16 December it has been brought down (and restarted 
by your script) a total of 20 times.  I have checked the access log each 
time it went down and always find evidence of the 3 awstats GET requests.

I am surprised that not more Interchange sites have reported being affected 
by this on this mailing list.  So far only 3 of us have reported 
experiencing this problem which would suggest that it is something peculiar 
to our installations, and yet I am sure it isn't.  If anyone else is seeing 
the same problem with there Interchange site going down please post a brief 
reply to this thread - thanks.

> I still think there is a problem somewhere, either in apache,
> mod_interchange or interchange, however I'm not sure how to go about
> finding the issue without an easy to reproduce case.

> Once someone can come up with a reproducible case I will look into a
> fix closer.
I'll let you know if the DropRequestList stops the problem - I suppose that 
will at narrow down the cause to the xmlrpc POST requests...  Thanks.

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