> From [EMAIL PROTECTED] Thu Sep 30 16:19:20 2004
> Date: Wed, 29 Sep 2004 10:45:01 +0200
> To: <[EMAIL PROTECTED]>
> From: <[EMAIL PROTECTED]>(Walter Harms)
> Subject: LPRng: LPRng-3.8.27:  strange load problem
>
> Hi Patrik,
> i have a strange problem when the lpd has some load, sometimes
> (lets say 1:50 change) he suddely stops without any errormessage or other indication 
> whats going on.
>
> I have tried to reproduce the error but failed so far.
>
> are you aware of this problem ?
>
> regards,
> walter
>

When you say 'stop', do you mean it stops accepting jobs OR
it does not process any jobs that are in the queue?

To prevent denial of service attacks, LPRng will not fork more than a 
specified number of 'worker' processes at a time.  It is assumed that
doing so will cause the operating system to be unable to start additional
processes.  This 'high water mark' is controlled by:

# Purpose: maximum number of servers that can be active
#   default max_servers_active=1024  (INTEGER)

Note that this is, by default, 1024 (default).  You might want to try lowering
this to (say) 512 and see if this effects anything.

The problem here is that when the system goes into a heavy load,
lprng does not notice this,  but tries to perform as normal.  The
problem usually is noticed by processes that it 'forks',  which then
desperately try to fork subprocesses,  which do not work,  which,
after a while, (10 minutes), the worker process exits, LPRng sees
the exit process,  decides it can now do more work,  and MAY start
a subprocess.

To ensure that this does not become a 'permanent' condition,  periodically
LPRng will do a scan of print queues, looking for work.  This scanning is
done by ONE process, which will send a message to the master LPD process,
which keeps a list of all the queues which need work.

When the load goes down,  this 'queue list' is scanned for the oldest entry,
and a subprocess is forked to handle this.  Umm... if a large number of queues
are ready to be serviced,  the lpd server might try to start a lot of them,
leading to the same problem as before.


As I say,  this usually only occurs under a very high load condition with
a lot of processes being created and then not exiting.

I have observed with on several Web Servers running Apache and CGI scripts.

Patrick

Patrick Powell                 Astart Technologies
[EMAIL PROTECTED]            6741 Convoy Court
Network and System             San Diego, CA 92111
  Consulting                   858-874-6543 FAX 858-751-2435
LPRng - Print Spooler (http://www.lprng.com)

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