[Info-vax] LAT service availability timeout after shutdown

[John Santos]

In article <pslkj596cdne5gd3u8qbs40qtnt0ji6tnv at 4ax.com>, gerry77
@no.spam.mail.com says...> 
> On Tue, 29 Dec 2009 00:09:19 -0800 (PST), Bob Gezelter <gezelter at rlgsc.com>
> wrote:
> 
> > As David Sneddon noted, a DELETE SERVICE <servicename> command in
> > LATCP will make the service disappear on the other nodes.
> 
> His suggestion actually resolved my problem and I'm about to write some DCL
> to obtain from LATCP a list of my local services, in order to delete them
> one by one because there is no wildcard support in LATCP, as you have noted.
> 
> > - SET NODE/STATE=OFF
> > 
> > Service(s) remain "AVAILABLE" persist, even though LATACP on service
> > providing node has exited.
> >
> > There are some other experiments that I would do if I had the time,
> > which I do not at this instant. The observed behaviors appear
> > consistent with LAT service announcement messages being sent upon
> > Service creation/deletion, but NOT on a LAT node shutdown.
> > [...]
> > Then again, the list of services is not generally highly variable. One
> > can get the same effect as one would using wildcards by keeping a list
> > of services created and issuing a DELETE SERVICE command on each
> > service during node shutdown. If shutting LATACP manually, it is up to
> > those shutting down LATACP to behave in a responsible fashion and do
> > the DELETE SERVICE commands.
> 
> This indeed is not a good thing IMHO, because if a node or some of the
> network fails, there will be stale services lying around for a very long
> time. Deleting services before shutdown is a good idea, but it does depend
> upon both (good) management and correct system shutdown. Instead, some sort
> of timeout (a lot shorter than 12 hours), would take into account every
> problem. Moreover I've discovered that I cannot force a node to forget some
> stale service, i.e. DELETE SERVICE is effective only on the offering node,
> so just suppose I've a crashed system or some network problem that prevents
> me from quickly restoring a LAT service, the only way I have to make it
> disappear is to stop and restart the LAT driver on all the remaining nodes,
> thus forcing a disruption of all the working services too. I'm still asking
> myself if this so long timeout is a specific feature of LTDRIVER on OpenVMS
> or not. Maybe DEC terminal servers behave differently and are quicker to
> update their service list whenever they stop to receive the advertisement of
> some service that has gone away.
> 
> Thank you very much for the experiments you've made for me. :)
> 
> Bye,
> G.

Ummm, why is this actually a problem?  A client will notice a service
has gone away when it actually tries to use it.  If it doesn't try
to use it, why would you care?


-- 
John