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Re: [ic] mod_interchange and Apache MaxClients


On Wednesday, November 16, 2005 6:09 PM, suppressed wrote:

From: suppressed
[mailto:interchange-users- suppressed On Behalf Of
Kevin Walsh
Sent: Wednesday, November 16, 2005 9:12 AM

John1 suppressed wrote:
I believe that my site only actually ceases to respond once
MaxClients is reached.  Even though MaxClients is no doubt not the
underlying cause of the problem (but a symptom) what I would like
to do is automatically restart apache and interchange when
MaxClients is reached as this would keep website downtime to a
minimum.

You'll probably find that it's the other way around.  A pause in
service will cause further requests to be queued until the
MaxClients limit is reached.  If you wait for the MaxClients warning
before restarting Interchange then you will probably loose a lot of
user sessions in the interim.

I have determined in my case that it is not a MaxClients issue and
that just masks the problem.  My site still went down when MaxClients
was at 1024.  I did not get the MaxClients reached error at that
time, so I believe that MaxClients is only reached after the site is
down for a certain amount of time, most likely the amount of time it
takes to queue up that many clients.

I think it would be better to find the cause of the service
interruption and correct the underlying issue.  That's a task that
can only really be performed on a system that exhibits the problem,
of course, and it'd be difficult to estimate the time it might take
investigate and correct the issue.

I will continue to look into this issue and will only be running my
restart script when I'm away from the computer, to keep the site live.
However when I'm at the computer I will be waiting for the site to go
down so I can try to figure out what is causing the problem.

Kevin asked me to try the following:

You could set up a cgi-bin executable on a "testing" subdomain, along
with a "/cgi-bin/foo" alias on the end of your Catalog line.  if/when
Interchange stops responding, try sending requests through the CGI. If
the requests fail there as well then the finger points at Interchange,
otherwise it would look more like a mod_interchange (or Apache module
API) issue.

I will be trying the above steps the next time the site goes down to
see if we are seeing a problem with Interchange or a problem with
Apache/mod_interchange communicating with Interchange.  John and Jeff
it'd be great if you could do the same on your systems so we have more
then one result.

I will try to do this but may take me a while to remember/figure out how to do this - if you have time to post a snippet from you catalog config once you have done this it would be appreciated.

Also post your mod_interchange section for Apache so we can see if we
are all communicating with IC via unix sockets or tcp.  My config is
as follows:

<Location />
       SetHandler interchange-handler
       InterchangeServer 127.0.0.1:7483
       DropRequestList /default.ida /x.ida /cmd.exe /root.exe
       OrdinaryFileList /w3c/ /webstats/ /rss/ /classes/ /banner/
/images/ /guides/ /nav/ /ebay/ /guides/
</Location>

I am running via Unix sockets:
<Location />
InterchangeServer /usr/local/interchange/socket
...
</Location>

I have recently also enabled Inet mode from localhost by adding the following to my interchange.cfg:

Inet_Mode Yes
TcpMap 127.0.0.1:7786 -

The reason I did this was to allow me to telnet to Interchange when the site stopped responding to try to verify whether Interchange was still responding. When the site last stopped I did "telnet 127.0.0.1 7786" and I did get a connection, but I wasn't sure what else to input in the telnet session confirm whether Interchange was responding. Is this a useful test and if so, what should I key into the telnet session to confirm Interchange is alive and well? Thanks


	
	
		
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