[cups.development] CUPS can't handle high frequency of request!

Michael Sweet mike at easysw.com
Thu Jul 15 02:50:38 PDT 2004

Sanjay Mishra wrote:
> My system has high traffic for creating PDF files and I have a CUP 
> filter (myCUPSFilter)which simply transfer the data it received to 
> pictwpstops filter. After around 100 transactions I find that CUPSD 
> throws errors like 'can't fork myCUPSFilter".

That's an OS error - basically you have too many processes running
or too much VM is in use.

> But when I slow down the traffic a bit( reducing the freqeuncy with which the request was 
> received) the number of transactions increased to 600 and more without 
> any error. Could any of you give any idea where to look for.
> I also increased the MaxClient value to 1000 and MaxClientPerHost to 300 
> as I wanted a different number than 10% of MaxClient. This change alone 
> increased the transaction count to 140 without errors.
> Is it that CUPS can't handle high traffic and client should control the 
> frequency of the request? Or there are some configuration parameters 
> that I missed out and must do to run my application.

Without knowing more about your configuration (both hardware and
software), it is hard to say specifically, however the error that
you are getting indicates that you have more processes running
or more VM in use that can be supported by your system.

If it is a matter of running too many jobs at the same time, the
FilterLimit directive can be used to throttle that back, however
I don't know if that will help in your case or not.  The size of
the job history could also be an issue, as each fork() effectively
duplicates the VM of the server before it does an exec() of the
filter program - check the MaxJobs and PreserveJobHistory values.

The CUPS server can certainly handle high traffic situations -
that's why you are running into this issue! :)  (otherwise the
jobs would not be coming in fast enough to matter...)

Michael Sweet, Easy Software Products           mike at easysw dot com
Printing Software for UNIX                       http://www.easysw.com

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