An open discussion list for topics related to the eduGAIN interfederation service.

[Tomasz Wolniewicz <twoln AT umk.pl>]

Hi All,
   Here I am, reopening this thread. Sorry for the length of what follows.

A quick summary first.
The current "hard" approach to eduGAIN aggregation is that if we spot a
validation error then we mark the entire feed as broken and reject it.
There have been voices in this thread pointing out that rejecting an
entire feed of hundreds of entities because of a single offending entity
is much too harsh and that perhaps eduGAIN MDS should filter out
individual entities instead. This mail is primarily addressed to
supporters of this "soft" approach.

I am a strong advocate of the "hard" approach so I will put together my
views why this is good and "soft" is bad, I am sure there will be
opposite opinions as well. I will not hide that my true intention is to
convince the SG to the decision supporting the "hard" solution and have
this subject closed for at least a year.

Pros for "hard".

a) eduGAIN metadata profiles specifies the requirements for a correct
feed and does not have a notion of a semi-correct one. Accepting
something which is not correct and making decisions on what can be fixed
and how should not be something for the central aggregator to do.

b) This approach is clear and not open to any interpretations.

c) The "hard" approach does not do any real harm - if we stick to the
rule that ValidUntil should not ever drop below 4 days, the federation
should have plenty of time to fix the feed before the cached copy might
be dropped.

d) This approach is very easy to implement, but perhaps this should not
be a deciding factor.

Cons against "soft". These really are the questions that automatically
pop up, for which we will need to invent answers (read - new regulations).

a) If we decide that a single entity can be dropped, what do we do if
there are 2, 3, 100? Where is the limit?

b) How long do we tolerate errors in a feed, should there be a time
limit or do we just let it run indefinitely? If we set the limit, will
the situation be that much different from having this time limit being
equal to 0 which is another formulation of the "hard" approach.
Eventually the limit will arrive and then what - drop the whole feed on
the floor and leave nothing?

c) If a federation feed suddenly has corrupt data about an entity that
previously was OK what do we do? Keep the correct copy of this entity in
metadata or simply drop it? We definitely cannot keep the entity longer
than the validUntil of the last correct metadata feed, therefore to keep
we would have to implement per-entity valid-until counters and separate
per-entity warnings. This makes the system quite complex.

d) The "soft" solution supports a lax approach to the way that
federation cooperate within eduGAIN and we should not encourage that.

Cheers
Tomasz

-- 
Tomasz Wolniewicz              twoln AT umk.pl
http://www.home.umk.pl/~twoln

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