perfsonar development work

[Nicolas Simar <>]

Jeff W. Boote wrote:
> Vedrin Jeliazkov wrote:
>
> > Hi Nicolas, All,
> >
> > Support for perfSONAR service redundancy hasn't been much discussed up 
> > to now
> > AFAIK. This might make it rather tricky for quick 
> > implementation/deployment.
> >
> > As far as perfsonarUI is concerned, we can imagine the following 
> > procedure:
> >
> > 1) LS provides info in some pre-defined and well known way whether a 
> > given
> > service has several instances and where they can be reached;
>
>
> The LS is the easy one in the list. Multi-LS has been planned from day 
> one. That is the way to do redundancy for the LS. It is designed to work 
> that way. (Granted, that functionality was not put in this release - but 
> it is designed and developed. I don't recommend trying to shoe-horn 
> something into this release.) Adding additional state information into 
> the client is in my opinion a "bad idea" (tm). ;) This will only make 
> transitioning to the next version more difficult.

Definitely. It is a functionality for a later one.

> > 2) perfsonarUI randomly selects one of those instances and sends a 
> > query; if
> > the service returns some unexpected error or the query timeouts, then the
> > client asks another randomly chosen service instance; this process 
> > continues
> > until either the query is answered or the list of available service 
> > instances
> > is exhausted;
> >
> > In fact, this pretty much follows the way how DNS stuff works.
>
>
> True - but each client does not implement that itself with its own 
> algorithm. There is a standard resolver library interface. That is 
> really the last component that needs to be created for the Multi-LS: A 
> client library that uses a 'standard' boot-strap algorithm to find the 
> single ls instance it needs to register with. Then that instance is 
> responsible for propagating the content to the global state.

What would happen in the single LS instance it needs to register with is 
down?
What will happen with the info (will it dissapear, does the service has 
to find out another single LS?)

Cheers,
Nicolas

> jeff
>
> > Kind regards,
> > Vedrin
> >
> > Nicolas Simar 
> > <>
> >  wrote:
> >
> > > Hi,
> > >
> > > for the deployment of the MDM service on GEANT, the DANTE operation 
> > > team mentioned that they would wish to have the services backup-ed on 
> > > a second server.
> > >
> > > How can this be done? (a) for the next three months, (b) for the next 
> > > release?
> > >
> > > 1) SSH telnet MP - two deployments each contacting the routers. No 
> > > issues foreseen.
> > >
> > > 2) RRD MA - two deployments, how do they access the data? The 
> > > original DB might be on another server, how do you synchronize those? 
> > > Do you foresee another way of doing this?
> > > Obviously if the server where the original data are is down, we can't 
> > > do anything except if there are two instance capturing the data.
> > >
> > > 3) L2 status MP - two deployments, each accessing the XML file stored 
> > > locally for one server, in another place for the other.
> > > Obviously if the server where the original data are is down, we can't 
> > > do anything except if there are two instance capturing the data.
> > >
> > > 4) SQL MA - two deployments. What do you suggest to do with the DB? 
> > > Stored where? Any suggestions.
> > >
> > > 5) LS - how two instance of the LS could have the same information? 
> > > (can the services register to two LSes at the same time)
> > >
> > > 6) How would the LS advertise the fact that there are two 
> > > web-services offering the same information?
> > >
> > > 7) How does the visualisation tools react to have two services 
> > > offering the same information? How would they react when one goes down?
> > >
> > > Thanks a lot in advance
> > >
> > > Cheers,

--
Nicolas
______________________________________________________________________

Nicolas Simar
Network Engineer

DANTE - www.dante.net

Tel - BE: +32 (0) 4 366 93 49
Tel - UK: +44 (0)1223 371 300
Mobile: +44 (0) 7740 176 883

City House, 126-130 Hills Road
Cambridge CB2 1PQ
UK
_____________________________________________________________________