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Re: Combining THREDDS and Pydap services



Roy,
If you run the Python servers under WSGI it should be
fairly easy to write a custom dispatcher that will do
anything you need.  You could also run the Java
Servlet requests through your WSGI dispatcher using
something like Paste proxy.

-Phil

--- Roy Mendelssohn <address@hidden> wrote:

> > Date: Mon, 27 Nov 2006 17:43:43 -0800
> To: address@hidden
> From: "Roy Mendelssohn" <address@hidden>
> Subject: Combining THREDDS and Pydap services
> CC: "Roberto De Almeida" <address@hidden>,
> address@hidden,
>         address@hidden
> 
> 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: address@hidden (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."


Phil Sharfstein
 GODAE Project Manager
 Fleet Numerical Meteorology and Oceanography Center
 7 Grace Hopper Ave, Stop 1.
 Monterey, CA 93943
 831.656.4525
 address@hidden

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