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RE: Number of connections



Here's a problem of openldap usage or configuration. Hope
someone will be able to answer. Much appreciated.

We run OpenLDAP 2.0 on Redhat Linux 7.0. 

With the command "host 127.0.0.1" defined in ldap.conf,
we can do ldapsearch & ldapadd successfully following 
the Quick-Start Guide of OpenLDAP 2.0. We understand this
is for the client & Server co-located mode on the same machine
and the ldap client is using the "localhost" for ldapsearch/ldapadd .



However, when we move to client and server on two machines 
(connected via private TCP/IP LAN), we encounter problems:

First we verify we can ping each other between the two machines
, i,.e. client machine can ping the server ( IP address : 192.168.1.4)
, meaning the two machines are mutually reachable on IP level.  

Second, we change the host command to be "host 192.168.1.4" in 
client machine's ldap.conf file to signify the external ldap server's
IP address of 192.168.1.4. When we issue the ldapsearch or ldapadd 
command on client machine, we got the error messages of 
"ldap_bind : can't contact ldap server" ! We're stuck at this point.

We try other means after reading the comment on openldap-bugs (ITS#322).
As such, we add "-h 192.168.1.4" at the end of the ldap search or ldapadd,
for example :

ldapsearch -x -b '' -s base '(objectclass=*)' namingContexts -h 192.168.1.4

We still got the same message of "ldap_bind : can't contact ldap server".

Why we're getting these error messages when we've followed the "Quick Start
Guide" ?

Is it because that we have to use hostname instead of IP adddress in the
"-h" option or
in the "host" command of ldap.conf ? I doubt this is the problem as the
ldap.conf(5)
document clearly says HOST can be followed by IP address.

Yet Chang

-----Original Message-----
From: James Bourne [mailto:jbourne@MtRoyal.AB.CA]
Sent: Monday, April 15, 2002 3:39 PM
To: Evaristo-Jose Camarero (ECE)
Cc: 'OpenLDAP-software@OpenLDAP.org'
Subject: Re: Number of connections


On Mon, 15 Apr 2002, Adam Williams wrote:

> >Can anybody tell me how many simultaneous connections can be served 
> >by the openldap server (2.0.23 with Red Hat Linux 7.1).
> >I have seen the code and it seems that there is a thread pool with 32 
> >threads. Does it mean that server only can attend 32 connections at the
> >same time?
> 
> Yes.  But answering a request should be very quick,  and the thread then
> processes the next request.  I suppose you could try increasing the
> thread pool, but I don't know if that will work.  In actuality (ever
> case I've seen) 32 is alot of concurrent queries.
> 

Yes, increasing the thread pool does work fine.

You can set the number of threads and concurrent connections with:

threads		<number of threads to run at max>
concurrency	<number of concurrent connections to allow>

One other thing to note, slapd uses select, and is therefore limited to
1024 concurrent connections due to the limit of __FD_SETSIZE (I ran into
this in some scalability testing I was doing).  If it were using poll then
the limit would be more scalable.

Of course, if you can run a read server with 1024 connections, I'm sure
you're doing fairly good...

We generally set concurrency slightly less then threads.

Regards
James Bourne

-- 
James Bourne, Supervisor Data Centre Operations
Mount Royal College, Calgary, AB, CA
www.mtroyal.ab.ca

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