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[Metadata-Support] Re: optimizing metadata refresh

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  • From: Tom Scavo <>
  • To: "" <>
  • Cc: Tom Scavo <>
  • Subject: [Metadata-Support] Re: optimizing metadata refresh
  • Date: Tue, 24 Mar 2015 11:24:25 -0400

Oops, I see from the responses from Scott and Ian (which are
appreciated) that perhaps I did not phrase my question correctly. Let
me try again.

The characteristics of the aggregate are fundamentally different than
the characteristics of the entity descriptors. The latter are not
expected to change as frequently as the aggregate, not even close. The
aggregate changes almost every day whereas an entity descriptor can go
for months without change. My question is: Will the implementation
take advantage of this, and if so, how?

I understand the per-entity metadata server will refresh it sources
regularly and often, but why should that force a refresh at the
client? Can and will we use HTTP Conditional GET to eliminate (what
seems like) unnecessary metadata refreshes?


On Mon, Mar 23, 2015 at 2:21 PM, Tom Scavo
> On the production server (which serves aggregates), we
> have the following attributes on the root element:
> /md:EntitiesDescriptor/@validUntil? (currently 14d)
> /md:EntitiesDescriptor/@cacheDuration? (currently NONE)
> I've always thought the optimal validUntil value should be around 4
> days but we're a long way from achieving that goal. On the Metadata
> Consumption wiki page [1], we recommend that clients attempt a refresh
> every hour (which is cacheDuration, right?). Since metadata is
> typically signed once a day and the server supports HTTP Conditional
> GET, I'm not sure that is optimal either (but I'm not too concerned
> about it).
> On the beta server (which serves per-entity
> metadata), we have the following attributes on the root element:
> /md:EntityDescriptor/@validUntil? (currently 14d)
> /md:EntityDescriptor/@cacheDuration? (currently 6h)
> I doubt these values are optimal. (This is a beta server, which is why
> I haven't brought this up before now.) It's a fact that per-entity
> metadata doesn't change near as often as aggregate metadata. Should
> this fact be factored into the parameters somehow?
> My gut tells me that validUntil should be large while cacheDuration
> should be small. Does this sound right?
> Tom
> [1]

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