[Info-vax] LAT service availability timeout after shutdown

[Bob Gezelter]

On Dec 28, 1:14 pm, gerr... at no.spam.mail.com wrote:
> Hello all,
>
> I'm a Hobbyist and I just started to play with LAT services, but I haven't
> any terminal server, so I'm using only host systems (both VAX and Alphas).
>
> I've noticed that even after I switch off one of those systems, the others
> keep showing the services offered by the former as "Available". If I try
> something like SET HOST/LAT that service obviously becomes "Unavailable", at
> least on the system on which I try the command, but remains still visible.
>
> Only after about 12 hours, the services offered by a powered down system
> effectively disappear from the list kept by the other nodes. It was my
> understanding that _shortly_ after a service is gone it should disappear
> from the list of available services (and it seems an obvious thing too),
> anyway to me 12 hours does not properly seems a short period of time. :-)
> I wonder if true terminal servers behave like this or differently...
>
> SYS$MANAGER:LAT$SYSTARTUP.COM has the following on every node:
>
> $ lcp := $latcp
> $ lcp set node /connections=both /noservice_responder /ident="xxxxx"
> $ lcp create service /ident="xxxxx"
> $ lcp set node /state=on
>
> The list of available services is obtained with:
>
> $ lcp := $latcp     !just once, obviously
> $ lcp show service
>
> Every service is actually offered by only one node (OpenVMS V7.2).
>
> How can I shorten the time between a system shutdown and the removal of its
> services from the list kept by other nodes? Do there is something I can put
> in SYS$SYSTEM:SYSHUTDWN.COM to signal other nodes about the shutdown event?
> I've read the relevant manuals, but I haven't found anything useful.
>
> Thank you very much,
> G.

Gerry,

As David Sneddon noted, a DELETE SERVICE <servicename> command in
LATCP will make the service disappear on the other nodes.

I did a few quick experiments (commands in LATCP unless otherwise
noted):

- CREATE SERVICE TEST

Service appears on other nodes almost instantly.

- DELETE SERVICE TEST

Service disappears almost instantly on other nodes.

- 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.
Unfortunately, with all due respect to the original implementor(s) of
Super-LAT (the LAT implementation that supported both host and server
LAT connections, first released at 5.5 as I recall), LATCP does not
support a wildcard on DELETE SERVICE <servicename>.

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.

- Bob Gezelter, http://www.rlgsc.com