[Planetlab-users] Slices on a node

[Lluis]

> On Mon, 9 May 2005, Lluis wrote:
> 
> > Hi all,
> >
> > I want to put a little program on a node that should tell me 
> > whenever a new slice is started or stopped on that node.
> 
> right now there isn't really a notion of a slice being 'started 
> or  stopped' on a node, just 'created or not'.
> 

well just having notice when a slice is created or destroyed on a node would
be great

the point I want to reach is that as the slice 's' can have the addition of
new nodes or the removal of old ones, I'd like to know the status of the
available nodes on the slices.

that is, what i want to do is maintain an overlay multicast (probably
araneola) informed of the joins and leaves of a multicast group (represented
by a slice, in my case; 1 slice <-> 1 mcast group).

so, to avoid polling everytime PlanetLab Central for the status of the
different slices (the nodes currently "associated"), and as there is no
"callback method" for the join/leave events that i'm aware of, I plan to put
a little program on each node that will inform on the join/leave events of
each node on the slices.

the only check that *must* be done on PLC is about the addition of new nodes
(as they won't have the little program I said, giving by the way that all
the "old" nodes already have the program running...).

as you can see, the problem is that i'd like the overlay network to be
informed of the nodes that belong to a slice (the nodes of the multicast
group), and that's the only way I see that would work without overloading
PLC.


> > Putting that program on several nodes, I want to be aware of 
> > what's on each node and do some "callbacks" whenever something 
> > changes (inform some other nodes), without having to ask 
> > PlanetLab Central every time (I should ask PLC only for those 
> > new nodes that my program is not on).
> >
> > Do you know if there's any way to do that? Somewhere to look 
> > at?
> 
> there are ways of asking the Node Manager for the list of slices 
> currently created on the node, but they have mostly been used for 
> internal monitoring and thus aren't documented anywhere (this 
> will be fixed in the near future as the NM interface solidifies).  
> for example, you can read from the URL
> 
> http://localhost:813/live_slices
> 
> to get a CSV-format list of slices and the agent that created 
> each slice  (pl_conf in almost every case).
> 

I tried to look at the 813 port remotely on a planetlab node, but it refuses
the connection, I suppose that it only works from a local connection...
well, i can't try it now, as I don't have my ssh key available here... i'll
try later

Is this code on the CVS? (I looked through it, but it has a lot of dirs and
I don't know what much of them are) I mean, the code that gets that
information an presents it to the user... i'd like to use that API, even if
it's not already "standarized"... or at least, give it a look


> > I would also like to have access to the ssh key of a slice (to 
> > do some sort of encrypted multicast communication), but I think 
> > it's not available from inside de PlanetLab nodes.
> 
> the keys are available on the nodes, but only the keys associated 
> with your slice are accessible by default.  i'm not sure that ssh 
> public keys can be easily used outside the ssh applications 
> though, they're not quite in the same format as, say, openssl 
> uses (PEM).
> 

well, that's a problem then... as I don't know any other way to use a
"group" encryption without having to put "new information" (sending a new
token/key to each node, through unicast communication...)

Thanks for all,
   Lluis

-- 
--
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