[Paraview] paraview - client-server

joseph insley insley at mcs.anl.gov
Fri Feb 5 17:58:59 EST 2010 

Hey, Berk,

I will need to dig around for them, but I have a few scripts that I  
have used to do this.  Here is the basics of how they work.

We have a scheduled resource that requires OTP.  I have a script that  
I run on my local host, which will first prompt me for how many nodes  
and how many minutes that I want to run my job.  It then prompts me  
for OTP and ssh's to the login node of the resource.  There it runs a  
script that submits a job to the scheduler to run a wrapper script  
around pvserver.  This pvserver wrapper script figures out which node  
is the head node of the job.  This is returned to the original script  
on my local host.  The original script then uses this information to  
set up an ssh tunnel from the local host through the login node to the  
head node where pvserver is listening (prompting for OTP again.)    I  
can then connect my paraview client to the pvserver through the tunnel.

So, I run this local script, get prompted for OTP twice (once for  
launching pvserver, and again to establish the ssh tunnel) and then  
connect paraview client to pvserver.  There are some things that may  
be resource/scheduler specific, but if folks are interested I can dig  
up these scripts and share them.

joe.

On Feb 5, 2010, at 1:13 PM, Berk Geveci wrote:

> I was thinking about this. Is it not possible to run a script that  
> starts the ParaView server, figures out where the first node is and  
> then sets up an ssh tunnel to that node through the login node?
>
> On Fri, Feb 5, 2010 at 1:46 PM, pat marion <pat.marion at kitware.com>  
> wrote:
> If admins are concerned about opening ports than maybe you should  
> use ssh tunnels instead of portfwd.  I like to recommend portfwd  
> because I find it simpler to use, but usually an ssh tunnel can work  
> just as well.  And you don't have to worry about killing portfwd  
> when your done.  If you can get a ssh tunnel to work then should be  
> able to setup the tunnel in your custom command when starting the  
> server.
>
> Pat
>
>
> On Fri, Feb 5, 2010 at 1:27 PM, Rakesh Hammond <rakesh.hammond at googlemail.com 
> > wrote:
> Hi,
>
> Thanks for your replies - I think the plan is to have two queues in  
> our new machine (parallel and interactive). What Pat described here  
> is what we have been thinking about, just thought there must be a  
> more elegant solution than this - for example, in VisIt you don't  
> have to include the portfwd bit. Perhaps some thing to consider for  
> future PV releases?  I assume these kind of issues are common in  
> production platforms?
>
> Another point to consider is, from a procurement point of view,  
> people don't really care about visualization, all they want is more  
> TeraFlops etc and then expect the visualization to be fitted into  
> the system (ie : no separate network between login and compute, only  
> logins will see the file systems etc)
>
> I did set it up to do client-server in reverse, some direct  
> responses to what is suggested below.
>
> You mentioned generating MOAB job scripts on the fly through a pv  
> xml input dialog.  All you would need to do would be add some extra  
> code to your job script template.  The extra code would generate a  
> portfwd config file with a port chosen by the user.  The user would  
> have to pick a port number other than 11111, a random port that  
> hopefully is not in use.  When the start server button is clicked on  
> the client it could run a custom command that ssh's to a login node,  
> starts portfwd with the custom config file, and submits the MOAB  
> script.  Now the user just waits to pvserver to connect back to the  
> login node which is forwarded straight to the workstation.  If the  
> compute node can't connect to the login node by name (`hostname`)  
> you can use /sbin/ifconfig to figure out the exact IP.
>
> Yes - agreed, only problem is sys admin folks are very funny about  
> opening several ports - I think I have to come up with some clever  
> way to make them think, they are not opening many ports !  We  
> thought we could keep a log of what is available and what is used,  
> so each time it connects it can work out which ones to use (this may  
> avoid the use of random port number that is "hopefully" not in use)
>
> I can't think of an elegant way to kill portfwd when the session is  
> over, but you can probably come up with something.  Sorry I can't  
> offer any specific details.  You might want to read this wiki page  
> too, it describes such a system in use:
>
> Yes - this will be  an issue, but we thought that we could just kill  
> the portfwd job at the end when MOAB scripts finishes.  The portfwd  
> will be started at the user level - so the user should be able to  
> kill their own jobs as part of the script (well that would be the  
> theory!)
>
> When I get something to work, I will post some thing here on how I  
> did it....
>
>
> Regards,
> Rakesh
>
> On Thu, Feb 4, 2010 at 3:05 PM, burlen <burlen.loring at gmail.com>  
> wrote:
> Hi,
>
> I have used ssh for this on such systems. As long as the batch  
> system gives you exclusive use of the set of compute nodes(usually  
> the case), you shouldn't have to worry about ports being used by  
> others because the tunnel is through your ssh connection. It's not  
> automated though. Here is how I do it:
>
> I use two terminals on my workstation, in the following denoted by  
> t1$ and t2$, say fe is the front end on your cluster. In the first  
> terminal:
>
>   t1$ ssh fe
>   t1$ qsub -I -V -l select=XX -l walltime=XX:XX:XX
>
>
> XX is replaced by your values. The job starts and you're  
> automatically ssh'd into some compute node, which we'll say has  
> hostname NODE. In the second terminal:
>
>   t2$ ssh fe
>   t2$ ~C<enter>
>   -L ZZZZZ:NODE:YYYYY
>
>
> The ~C bit is an escape sequence that sets up the port forward.  
> ZZZZZ is a port number on your workstation. YYYYY is a port number  
> on the server that is not blocked by the clusters internal firewall  
> (see your sys admin). Now back to terminal one, and your waiting  
> compute node:
>
>   t1$ module load PV3-modulefile
>   t1$ mpiexec pvserver --server-port=YYYYY
>
>
> The module is what sets up the ld library path and paths for your  
> ParaView server install (see your sys admin). now paraview is  
> running on the cluster. You start the ParaView client locally and  
> connect over port ZZZZZ on localhost.
>
>
> That's what I do, if you come up with some automated script though  
> that would be killer.
> Burlen
>
>
>
>
> Bart Janssens wrote:
> On Thursday 04 February 2010 07:59:46 pm Rakesh Hammond wrote:
>
> I am no expert on this type of stuff, but I can see how this would  
> work
> - the question is if you have multiple users connecting at the same
> time, obviously you can't forward everything into 11111 for example.
>
>
>
> Hi Rakesh,
>
> If you use reverse connections, the compute nodes only need to be  
> able to connect to outside machines (i.e. the workstations). Turning  
> on NAT on a gateway machine, i.e. the frontend, should be sufficient  
> for that, and no port forwarding is needed. This works on a standard  
> Rocks setup, which enables the frontend as gateway by default.
>
> Cheers,
>
> Bart
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