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Re: SLAPD denial of connections under load

Quanah Gibson-Mount wrote:

--On Wednesday, August 11, 2004 11:32 PM -0700 Howard Chu <hyc@symas.com> wrote:

I suggest you separate the mail server from the LDAP server.  The high
load on the system from the mail delivery agent may be preventing slapd
from responding.

There isn't enough information here to determine a course of action. You
need to get more info before making suggestions on how to fix the problem.

My guess is that slapd is out of file descriptors or there are too many
outstanding connections. Using a program like lsof may help to determine
if that's the case. There is no way that any mail server can generate
more queries than slapd can handle when both are running on the same CPU.

I wasn't concerned about the mail server generating more queries than slapd could answer, I was more concerned about the mail server consuming enough resources that affected slapd's ability to respond. I would put running out of file descriptors, etc, into that category. ;) I suppose separation of services is a philosophy more than anything, but it is one I tend to apply in an infrastructure environment.

My first point still holds - it's not possible to make any substantive suggestions in the total absence of information about what the real problems are. After you've identified the actual problem, then you can think about whether separation of services is a necessary or sufficient solution. Offering suggestions before you know what the actual problem is amounts to witch-doctoring and black magic, and really isn't helpful in the long run. It does not arise from understanding, and it does not promote further understanding.

In the meantime - the limit on file-descriptors is per-process; I was talking about slapd running out of a private per-process resource, so sharing with anything else on the box is irrelevant. Also, unless one has explicitly set different process priorities on the mail and slapd server, there's no way that one server process can hog resources continually and prevent another process from running. And if someone has explicitly set process priorities to accomplish this sort of preferential execution, then they damn well ought to know that they did it and have taken that into account already.

 -- Howard Chu
 Chief Architect, Symas Corp.       Director, Highland Sun
 http://www.symas.com               http://highlandsun.com/hyc
 Symas: Premier OpenSource Development and Support