[moby] Re: [MOBY-dev] lease versus agent for registry updating

[Mark Wilkinson]

Hi Boris!

Thanks for the rapid reply!

That is how we had initially planned to do it as well, however the
consequence is that the registry (a) has to have a mechanism for
recording the number of failure occurrences, and this might be handled
differently by different underlying data stores, and (b) the registry
KNOWS that it contains service instances that are likely non-functional
but still reports them as being functional.

... Eddie just suggested an alternative to this alternative :-)  The
agent can deregister services that fail the URL lookup, but still retain
the URL and try them a few more times just in case they come back up
again.  That way the registry is always reflecting the *best*
information it can possibly know, but the burden of re-registering
services still falls on the Registry as much as possible.

That might be the way to go...

Other opinions?

M



On Fri, 2005-08-12 at 16:50 -0300, Boris Steipe wrote:
> Why not put the burden of the lease on the agent to combine the 
> advantages of both models? I.e. if service is down for less then a 
> specific time, it might not get deregistered but only flagged as 
> temporarily unavailable ... then un-flagged as it comes up again, 
> except if it's down for, say > 1week, then it gets deregistered.
> 
> $0.02
> 
> Boris
> 
> On Friday, Aug 12, 2005, at 16:38 Canada/Atlantic, Mark Wilkinson wrote:
> 
> > Hi all!
> >
> > Eddie and I are spending the day working on MOBY Central architecture
> > issues.  We've run into a question that has so many pros and cons that
> > we decided to toss it out to the list for other opinions.
> >
> > Keeping MOBY Central up-to-date:
> >
> > Method 1:  Agent
> >
> > An agent retrieves the list of SignatureURL's from the registry, and
> > crawls around retrieving the RDF from each of those URLs.  The RDF is
> > compared to what is in the registry, and updates/deletions are made.
> >
> > Consequence to service provider: a service providers machine goes down,
> > the service is deregistered (the agent can't retrieve the URL) and the
> > service provider must then actively re-register their services
> >
> >
> > Method 2:  Lease
> >
> > Services have a time-stamp in the registry and expire after X time.
> > They must then be actively re-registered.
> >
> > Consequence to service provider:  Service providers must set up a cron
> > (or whatever) that is aware of all of their *current* Signature URL's
> > and can call MOBY Central to re-register their services on a regular
> > basis.
> >
> >
> > Both solutions seem to put an unwanted burden on the service providers,
> > but the burdens are different in nature and frequency.
> >
> > Which of these seems preferable?  Are there solutions we haven't 
> > thought
> > of?
> >
> > ???
> >
> > Mark & Eddie
> >
> >
> > -- 
> > "Ontologists do it with the edges!"
> >
> > Mark Wilkinson
> > Asst. Professor
> > Dept. of Medical Genetics
> > University of British Columbia
> > PI in Bioinformatics
> > iCAPTURE Centre
> > St. Paul's Hospital
> > Rm. 166, 1081 Burrard St.
> > Vancouver, BC, V6Z 1Y6
> > tel: 604 682 2344 x62129
> > fax: 604 806 9274
> >
> > _______________________________________________
> > MOBY-dev mailing list
> > MOBY-dev at biomoby.org
> > http://www.biomoby.org/mailman/listinfo/moby-dev
> 
> _______________________________________________
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-- 
"Ontologists do it with the edges!"

Mark Wilkinson
Asst. Professor
Dept. of Medical Genetics
University of British Columbia
PI in Bioinformatics
iCAPTURE Centre
St. Paul's Hospital
Rm. 166, 1081 Burrard St.
Vancouver, BC, V6Z 1Y6
tel: 604 682 2344 x62129
fax: 604 806 9274