[Spread-users] varying number of spread servers

Ryan Caudy rcaudy at gmail.com
Thu Jul 15 18:00:05 EDT 2004


Responses inlined below.  Good luck.

Cheers,
Ryan

On Thu, 15 Jul 2004 12:45:58 +0200, anowa at freenet.de <anowa at freenet.de> wrote:
> Hi,
> 
> first of all, I want to describe what I need spread for.
> 
> I have a dynamically varying number of client computers which are
> sending some data to a server. The server also sends some data to the
> clients. So the clients are also acting as small servers. In this
> scenario the communication between all members is unicast. In future
> perhaps also multicast.
> 
> The communication is done on a WLAN and it is very important that
> the data send between all members is delivered reliably.
> Using WLAN it is possible that the connection is interrupted, as the
> clients are constantly moving.
> 
> So the problem lies in the configuration of all spread servers.
> I planed to use one spread server on each computer (client and server).
> Is this suitable?
> 

This may be possible, but you should be very aware that the primary
cost of using spread is expensive daemon-memberships.  What this means
is that, every time one of your clients leaves the network, or
everytime the wireless network experiences small problems (i.e.
someone uses a microwave ;-) ), the messaging service may be
interrupted while Spread negotiates and installs a new daemon
membership.  Loss of individual members doesn't incur this penalty. 
Also, while the wireless medium is inherently broadcast (without
directional antennas, which I don't think are coming into play here),
it isn't everyone-to-everyone broadcast the way ethernet is.  You need
to make sure that your configurations are defined in such a way that
daemons in the same "segment" can all reach one another via broadcast.
 You might instead want to consider an architecture with a few
stationary, well-distributed nodes to be servers, even on a wired
network.

> Furthermore each spread server needs a list of all other spread servers
> in a section. But if another client joins or leaves the network the number
> of spread servers is changing and the configuration of ALL spread servers
> has to be updated.
> 

This isn't possible with Spread right now.  Instead, you should define
a configuration with all possible daemons.  There isn't actually a
limit on the number of daemons in a configuration (as far as I know),
just a limit of daemons actually in a membership of 128.  This might
work in combination with a dhcp for your WLAN.

> Are there any functions inside the C-API which I can use to add or
> remove a ip from a server configuration?
> Or is there another mechanism to achieve this goal?
> 

There is no mechanism currently provided to do this.

> Thanks for your help!
> 
> Best regards
> 
> _______________________________________________
> Spread-users mailing list
> Spread-users at lists.spread.org
> http://lists.spread.org/mailman/listinfo/spread-users
> 


-- 
---------------------------------------------------------------------
Ryan W. Caudy
<rcaudy at gmail.com>
---------------------------------------------------------------------
[Alumnus]
<caudy at cnds.jhu.edu>         
Center for Networking and Distributed Systems
Department of Computer Science
Johns Hopkins University          
---------------------------------------------------------------------




More information about the Spread-users mailing list