On 1/3/2011 10:53 AM, Roland Schweitzer wrote:
Hi,
We're starting to put together some "big" server-side configuration
catalogs (both with "lots" of dataset elements and "lots" of
catalogRef elements). We are wondering about the process TDS goes
through to read the catalog when is starts. What gets cached? Does
it have a way to know a referenced catalog is unchanged? When do
referenced catalogs get scanned? And so on.
Is there some documentation or a flow chart on how TDS initializes
itself?
Thanks,
Roland
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Hi Roland:
The sad answer is theres not much documentation. Weve been on the verge
of redoing the initialization sequence for a few years now, so weve been
waiting so we can document the clean, cool refactor instead of the
crufty, lame current one.
Anyway, the TDS reads in all the config catalogs at startup. It caches
all of them, and uses the "expires" attribute on the catalog to decide
if/when it needs to reread a catalog. It needs to read all catalogs,
including catalogRef, because it has to know what the possible dataset
URLs are, and there is no contract that a client has to read a catalog
first.
Obviously this doesnt scale forever. Ethan can probably fill in some
details.
see:
http://www.unidata.ucar.edu/projects/THREDDS/tech/catalog/v1.0.2/InvCatalogSpec.html#catalog
John
