[stunnel-users] scaling stunnel

Ben Hartshorne stunnel at green.hartshorne.net
Fri Oct 19 00:33:28 CEST 2007

addendum that I forgot.  My debian does actually have stunnel 4.09, I
just havn't gotten around to testing it yet (is there a compelling
reason to upgrade to 4.20 from 4.09?).  And I'm running debian on linux
2.6.16-2-686-smp.  ;)


On Thu, Oct 18, 2007 at 03:00:56PM -0700, Ben Hartshorne wrote:
> Hi,
> I am trying to set up syslog + stunnel in a large environment.  I am
> curious about the experience of members of this mailing list regarding
> how stunnel + syslog-ng scale.  
> I set up a test environment using stunnel 3.26 (because that's what is
> in my debian installation)[*].  I configured stunnel to run as a daemon
> (starting on boot), and syslog passes off messages and receives messages
> from localhost:514.  In the stunnel log, it tells me that there is a
> limit of 500 clients, and it seems that with stunnel 3.x, it must be
> recompiled to increase this limit.  I found some posts on this list that
> say that while stunnel 3.x uses select(), stunnel 4.x uses poll(), which
> is much more efficient.  So I figure that if I will have to roll my own
> package, I may as well upgrade to 4.x at the same time.  Agree?  If so,
> which version?  
> It's my understanding that this configuration will create a persistent
> connection between the client and server, holding it open until such
> time as syslog needs to send a message across it.  How many clients have
> you experienced being able to connect to the log aggregator?  My logs
> are rather sparse, so I expect I will hit a limit based on processor /
> filehandle / memory usage before I start overloading the local disk.
> Eventually, I realize that I will have to build a tree structure with
> intermediate nodes aggregating logs and passing them on to the central
> host, but I would like to know where people have hit that limit.  I
> would love to have ~5000 clients connected to each aggregating server.
> Is this within the realm of experience?  
> Does anybody have tuning suggestions for such high numbers of
> connections?  I saw one person mention on the mailing list that
> compiling without libwrap allowed him to pass ~2500 connections (though
> he didn't give a new ceiling).
> Thanks,
> -ben
> [*] I was actually impressed at how easy this was.  Aside from having to
> write my own /etc/init.d/ scripts to start the client and server, I
> could bring down either end of the stunnel connection, and things would
> just pick up where they left off when the tunnel was reconnected.  Add
> monit into the picture and you've got a nice resilient secure logging
> system.  Slick!
> -- 
> Ben Hartshorne
> email: ben at hartshorne.net
> http://ben.hartshorne.net

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> stunnel-users mailing list
> stunnel-users at mirt.net
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Ben Hartshorne
email: ben at hartshorne.net
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