Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Hi Joe, HTTP 1.1 can support requests for byte-range [a] subsets of a resource. This capability is optional so not all servers (or resources on a server) need support it. If you look at the HTTP response headers you get back from your [1] and [2] URLs you will see that [2] includes an "Accept-Ranges: bytes" header whereas [1] does not. The netCDF-Java library can open remote datasets available over HTTP, without downloading the entire file, if the server supports byte range requests for that dataset. [However, depending on the access pattern, this can be very inefficient as the client is doing the subsetting which may require multiple HTTP requests. For OPeNDAP access, the subsetting is done on the server and generally only requires one HTTP request.] Hope that helps, Ethan [a] https://en.wikipedia.org/wiki/Byte_serving On 6/10/2013 8:04 AM, H. Joe Lee wrote: > Hi, John & Ethan! > > Thanks for the help! > > Now I figured it out that the "location" tag of NcML does not work > with the on-demand NetCDF-3 file that is automatically generated by > "fileout_netcdf" module by OPeNDAP server like [1]. If I save the > NetCDF-3 file from [1] and put it in a regular HTTP server like [2], > the NcML works fine. > > For comparison, the URL [3] is the DAP response that NCDump in > ToolsUI can also recognize. Thus, I could make my NcML work by > dropping .nc as Ethan suggested. Since [3] works fine with NcML, I > have no reason to save and put it in a separate web server like [2]. > > However, I still don't know why OPeNDP fileout_netcdf module doesn't > work with NcML "location". What's the key difference between [1] and > [2]? It seems like an OPeNDAP sever configuration issue. I'm asking > opendap-tech mailing list to get some help. > > Regards, > > > [1] http://eosdap.hdfgroup.uiuc.edu:8080/opendap/data/hdf4/foo2.hdf.gz.nc > [2] http://hdfeos.org/foo2.hdf.gz.nc > [3] dods://eosdap.hdfgroup.uiuc.edu:8080/opendap/data/hdf4/foo2.hdf.gz > > -- > HDF: Software that Powers Science ============================ http://eosdap.hdfgroup.uiuc.edu:8080/opendap/data/hdf4/foo2.hdf.gz.nc GET /opendap/data/hdf4/foo2.hdf.gz.nc HTTP/1.1 Host: eosdap.hdfgroup.uiuc.edu:8080 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate DNT: 1 Connection: keep-alive HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Last-Modified: Tue, 02 Oct 2012 02:58:53 GMT Content-Disposition: attachment; filename="foo2.hdf.gz.nc" XDODS-Server: dods/3.2 XOPeNDAP-Server: bes/3.11.0, libdap/3.11.7, dap-server/ascii/4.1.2, fileout_netcdf/1.1.3, hdf4_handler/3.10.1, hdf5_handler/2.1.2, netcdf_handler/3.10.2, ncml_module/1.2.2, dap-server/usage/4.1.2, dap-server/www/4.1.2 XDAP: 3.2 Content-Type: application/x-netcdf Transfer-Encoding: chunked Date: Mon, 10 Jun 2013 18:55:04 GMT ============================ http://hdfeos.org/foo2.hdf.gz.nc GET /foo2.hdf.gz.nc HTTP/1.1 Host: hdfeos.org User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate DNT: 1 Connection: keep-alive HTTP/1.1 200 OK Date: Mon, 10 Jun 2013 18:53:42 GMT Server: Apache Last-Modified: Mon, 10 Jun 2013 13:56:13 GMT Etag: "a20b75-f0-4decd24c9da96" Accept-Ranges: bytes Content-Length: 240 Keep-Alive: timeout=2, max=200 Connection: Keep-Alive Content-Type: application/x-netcdf Content-Encoding: gzip -- Ethan Davis UCAR Unidata Program edavis@xxxxxxxxxxxxxxxx http://www.unidata.ucar.edu
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