[AG-TECH] AG2, moving from standalone to multi-machine

Thomas Uram turam at mcs.anl.gov
Wed May 14 02:42:00 CDT 2003


Hi Darran:

Hopefully some of your questions are answered by the room node 
configuration doc I sent out tonight.  You might also want to look at a 
poster we recently put together, since it nicely describes the AG2 
components ( http://www-unix.mcs.anl.gov/~turam/AHM-poster.ppt 
[unofficial location intentional]).

Questions that clearly aren't answered by the doc are answered below. 
 If you have more questions, please ask.

Tom



darran.edmundson at anu.edu.au wrote:

>Taking into account that I'm a newcomer to AG
>technology, could someone possibly describe how AG2 
>runs across multiple machines?   
>
The individual components in AG2 are SOAP web services, so they 
communicate with each other by making SOAP method calls to each other.

>(Or even just a 
>pointer to the relevent docs.)  I've got AG2 running
>standalone but can only guess about:
>
>- Does each machine hold a copy of the globus proxy 
>  certificate or just one?  If the latter, is this
>  the "node manager"?
>
The globus certificate and a valid proxy must exist on each machine in a 
RoomNode (multi-machine node).

>- Or do I run the nodemanager on each machine, adding
>  the appropriate service (display=VideoConsumer,
>  video=VideoProducer, audio=Audio)?
>
A node runs a single NodeService, one ServiceManager per machine, and 
some number of Services on each machine.  "Node Manager" sounds like an 
approximation of the Node Management user interface, which is used to 
configure the node components.

>- I'd love an explanation of what a node operator does
>  and what actually happens under the hood to bring an
>  AG2 node up.  
>
We are on a path toward simplifying the job of the node operator. 
 Presently, with the AG2 software, the node operator's job will roughly 
parallel the job in the AG1 world.  You'll get some hint of this from 
the room node configuration doc, since it talks about starting a node.  

For "under the hood" details, I'll point you at our design docs which 
live in the CVS repository.  While not yet complete, the documents might 
provide the insight you're looking for.

>
>I'm starting to get an inkling about AG2 from digging 
>through the source and reading the logs (e.g., how 
>services are downloaded from the nodemanager) but any 
>help to accelerate this process would be greatly 
>appreciated.  I can't help but feel that I'm missing
>a crucial piece of documentation that clarifies all.
>
>Less important questions:
>- Running standalone leaves me with several python
>  processes.  I would have thought that shutting down
>  the main venue client or selecting "kill services"
>  would terminate these, no?
>
You should see those processes die more reliably in the code currently 
in CVS, and hence in the next release.  Kill services is a debug option 
that was intended to kill Services, but not the NodeService or Service 
Manager(s), and I've noticed lately that it hasn't even been doing its 
intended job well.

>- Should I get a beacon up and running on the video
>  capture machine ASAP?
>
Getting a beacon up is a good idea to be able to track your multicast 
connectivity.  Since multicast is (presently) so critical to the 
operation of the AG, the beacon provides very useful feedback.

>- When running standalone on the capture machine, why
>  do I see two copies of my single camera when I visit
>  localhost?  
>
>  
>
I don't know about this one, though I've seen it discussed.  Someone 
else will likely pipe in and explain.




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