[Condor-devel] Inconsistency in collector plug-in (API).

[Todd L Miller <tlmiller@xxxxxxxxxxx>]

	The collector passes query ads to the plug-in.  However, the 
offline & absent ad plugin return immediately upon encountering an ad for 
which a hash key can not be made.  This means that queries to the 
collector that don't specify single machines are silently ignored by the 
offline / absent ad plugin (and probably others).  In particular, if an 
admin wishes to force a certain set of machines offline or absent, s/he 
will probably write a query ad with a constraint (e.g., all the machines 
in this cluster), and be unable to do so.

	Rather than just document this as a misfeature, we would like to 
change the API so that update() and invalidate() are called not once with 
a query ad, but once per ad being update()d or invalidate()d.  Doing this 
would obviously remove the need for plugins to duplicate the 
query-processing code, ensuring that both types of query ads (and any we 
might add in the future) are handled uniformly.

	This change would also allow us to add a meaningful return value 
to invalidate(), where the plug-in returning false would mean "don't 
invalidate this ad".  (It's not at all clear that "don't update this ad" 
makes sense, but we could add that as well.)  This would permit users (the 
BaTLab, in particular) to track machines that leave the pool, even if they 
do so "cleanly" -- that is, are killed with SIGTERM rather than SIGKILL.

	Please let us know what you think.

	(On another, related note, it appears that expire() already 
functions this way, but isn't part of the official API.  Should we merge 
it in as well?)

- Todd L Miller