[JDEV] scaling a single server?

[Stanislav Angelov]

I don't know what the limitation of Linux for the sockets are, but the
absolute limitation is 64k since the port value is 2 bytes wide. So, with
TCP/IP you cannot have more then 64k connections (this is a theoretical
maximum, in reality more limitations apply) even if you have a
server-machine that can handle the load.

Also consider this: it is typical for IM systems to have many users
connected to the server who do but not generating any traffic. It is natural
for the people to stay online just in case somebody wants to talk to them.
So, a very typical scenario for an IM server is to have thousands of users
staying passively online, taking up socket connections and not generating
any messages. You may end up with a server that processes nearly no data,
but all its resources are exhausted because of the users connected.

I strongly recommend connectionless protocols and UDP!

Regards,
Stanislav


----- Original Message -----
From: "Jacob O'Reilly" <jacob at clear.net.nz>
To: <jdev at jabber.org>
Sent: Thursday, February 03, 2000 9:27 PM
Subject: Re: [JDEV] scaling a single server?


> I can't give you any idea about scalability of Jabber, but I do know that
> the number of sockets a process can have open is tunable in the kernel.  I
> don't know for Linux (as opposed to the commercial Unices I've used)
whether
> that is a socket specific parameter or just a factor of NFILE.  I imagine
> that with that many users tho., a fair few parameters might need to be
> changed.
>
> One of the things I've seen software do to scale better (to thousands of
> concurrent users) is to use the UDP protocol -- and maintain the idea of a
> connection at an application layer.  This doesn't provide for the simplest
> coding, but given that your average user may not act to cause any traffic
> very often at all, it provides the least load on the server machine (in
> terms of kernel/network resources anyway).
>
> It seems to me that a system of tiering connections through to a server
> would provide the most scalability.  Can etherx run on a different machine
> from the Jabber server?
>
> -- Jacob.
>
> -----Original Message-----
> From: Russell Nelson <nelson at crynwr.com>
> To: jdev at jabber.org <jdev at jabber.org>
> Date: Friday, 4 February 2000 09:48
> Subject: [JDEV] scaling a single server?
>
>
> >I've got a customer with 25 lakh users.  In case you're not familiar
> >with the units they use in India (I wasn't), 1 lakh == 10,000.  They
> >also comma-ize in an original and inventive manner, so they have
> >2,50,000 users.  I'm trying to convince them NOT to implement a
> >proprietary system.  This should not be impossible since they have
> >developed a predilection to Open Source solutions.
> >
> >They want to add all 25 lakh users to Jabber all at once, and announce
> >it.  Clearly there is not going to be a ramp-up period to give them
> >time to gain experience with Jabber.  They need to know that it will
> >scale from the get-go.
> >
> >Obviously this is OS dependent.  My customer is running Redhat 6.1 on
> >a machine with 18GB of hard drive and 1GB of memory.  Those values
> >should not be the constraint.  I'm more concerned with the number of
> >sockets that can be open at any one time.  If Linux has a limit of
> >1,000 sockets, and they have (they estimate) 25 thousand users online
> >at any one time, that means they need 25 servers.  This is double-plus
> >ungood.
> >
> >Does anyone have any experience with how big a single Jabber server
> >can scale?
> >
> >--
> >-russ nelson <sig at russnelson.com>  http://russnelson.com
> >Crynwr sells support for free software  | PGPok | "Ask not what your
> country
> >521 Pleasant Valley Rd. | +1 315 268 1925 voice | can force other people
to
> >Potsdam, NY 13676-3213  | +1 315 268 9201 FAX   | do for you..."  -Perry
M.
> >
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