You could use Squid (proxy cache software) as a server-side accelerator
(reverse proxy) -- it allows a redirector script that allows you to
rewrite incoming urls into server urls using whatever criteria you want
(I use a perl script). If you are careful about caching, would speed
up your server as well.
Benno
Roy Mendelssohn wrote:
I apologize for the double post. I got my mail lists confused (old
age is setting in), I originally posted to support-thredds but meant
to post it here.
-Roy M.
Hi:
I am throwing out to the list a THREDDS related server problem that we
are trying to figure out relatively clean ways to solve, in the hope
that others may have some good ideas on how to accomplish this.
We are heavily invested in THREDDS
(http://oceanwatch.pfeg.noaa.gov/thredds/catalog.html) in particular
the cataloging and the data aggregation. Most of the links on that
page are not single files but many files (sometimes in the thousands)
being aggregated through time. This is a very useful feature for the
type of data we have.
Also, on an in-house server we have been testing Roberto De Almeida's
pydap implementation of OPeNDAP (http://pydap.org/). This server has
a lot of nice features that we are interested in, such as his wms
service and kml service from an OPeNDAP URL type expression.
So what is the issue. Clearly, on web pages that are developed in
house, where a user just clicks on a link, if we have both Pydap and
THREDDS running on the same machine, we can change the links to point
to the appropriate server. But for the more general public, or for
people using the links in scripts etc, we would like to have just one
basic link that depending on the file ending would go to the correct
place.
So right now if I wanted the second time period, full extent of one of
the files the URL would be:
http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/AT/ssta/1day?ATssta[1:1:1][0:1:0][0:1:2320][0:1:3200]
If I wanted an ascii file it would be:
http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/AT/ssta/1day.ascii?ATssta[1:1:1][0:1:0][0:1:2320][0:1:3200]
but what I would like to do is that if I give it:
http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/AT/ssta/1day.kml?0:1:2320][0:1:3200]
and it would know to switch-over to the pydap server and produce the
kml output (while still being able to view the file as a single file
through the THREDDS aggregation).
Now as given, it is unlikely to work since THREDDS is in the URL. But
suppose we had something like:
http://oceanwatch.pfeg.noaa.gov/ERD_Data/satellite/AT/ssta/1day.ascii?ATssta[1:1:1][0:1:0][0:1:2320][0:1:3200]
or
http://oceanwatch.pfeg.noaa.gov/ERD_Data/satellite/AT/ssta/1day.kmlATssta[1:1:1][0:1:0][0:1:2320][0:1:3200]
and want it so that in the ascii case it goes to THREDDS and in the
kml case it goes to Pydap.
Ideas we had:
1. Monkey with the appropriate section in the THREDDS java to redirect
when it recognizes the new service type, much as it does with WCS
services. Downside is we would have to monkey with every revision and
could mess up things in unexpected ways in the process.
2. At the apache or tomcat level, have the redirection made (is this
possible?) based on file type.
3. Some other solution?
A question I pose to Roberto (as he is copied) but may be of general
interest is if there is a way for Pydap to serve OPeNDAP served data
that is at another URL (even if on the same machine), much as THREDDS
can. It is this that would simplify what it would take for us to use
the aggregation capabilities in THREDDS with Pydap in our own internal
scripts as we can still views these as one file - or does anyone else
have general suggestions as how we might combine the desirable
features of each.
-Roy
--
**********************
"The contents of this message do not reflect any position of the U.S.
Government or NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail: Roy.Mendelssohn@xxxxxxxx (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
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