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.
yes, bob is correct. use opendap for remote access. On 10/11/2012 11:30 AM, Brian Schlining wrote:
Bob's response is below. -- Brian Schlining Forwarded message:*From:* Bob Simons <bob.simons@xxxxxxxx> *To:* Brian Schlining <bschlining@xxxxxxxxx> *Date:* Thursday, October 11, 2012 10:05:47 AM *Subject:* Re: ERDDAP bug I understand the issue that you are talking about. I would instead urge you not to use this approach. This approach has the implicit assumption that there is a static .nc file with the requested subset of the larger dataset and that NetCDF-Java can read specific bytes from that file. See http://www.unidata.ucar.edu/software/netcdf-java/reference/HTTPservice.html That is just not a good way to think about that file. Please request a .nc file from ERDDAP only if you want to download that .nc file. For your purposes, please use NetCDF-Java to access an ERDDAP dataset as an OPeNDAP dataset. This is what OPeNDAP was designed for and NetCDF-Java supports this *very* well. This approach will work *much* better, for a variety of reasons. Here is a code snippet: NetcdfFile ncFile = NetcdfDataset.openFile("http://beach.mbari.org:8180/erddap/griddap/erdRyanSST";, null); //note that there is no file extension at the end of the dataset's name //Then you can do what you want with the ncFile object. I will improve the documentation related to this. Thanks for pointing out this weakness in the documentation. I hope that clarifies the situation. If not, or if you have other questions about ERDDAP, please let me know. P.S. I am not on netcdf-java mailing list. Can you please post this response on the netcdf-java mailing list? Thank you. On 10/11/2012 9:31 AM, Brian Schlining wrote:Hi Bob, We're doing some work with ERDDAP and running into an issue using NetCDF-Java to access files served by ERDDAP. I think I understand the issue and know how to address it, so I'm passing the info onto you all so it can be addressed. So here goes: 1) ERDDAP allows one to download a NetCDF file by building a link appended with '.nc'. The link URL for the netcdf file would be something like http://beach.mbari.org:8180/erddap/griddap/erdRyanSST.nc. This works great for downloading the files. However, it does NOT work with the NetCDF-Java API; NetCDF-Java can normally read NetCDF files from arbitrary non-opendap http urls. 2) The reason it fails is because NetCDF-Java needs to know the size of the file being served. This requires that the HTTP response for a URL like http://beach.mbari.org:8180/erddap/griddap/erdRyanSST.nc to contain a 'Content-Length' field. ERDDAP is not sending that … here's a response header from ERDDAP (notice there's no 'Content-Length': HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Date: Thu, 11 Oct 2012 15:44:19 GMT Last-Modified: Thu, 11 Oct 2012 15:44:19 GMT xdods-server: dods/3.7 erddap-server: 1.38 Content-Disposition: attachment;filename=erdRyanSST_8571_f367_229e.nc Content-Encoding: Content-Type: application/x-download Transfer-Encoding: chunked 3) Since ERDDAP is running on Tomcat, the only way I know of to set the 'Content-Length' is to explicitly call 'response.setBufferSize()' in the servlet that returns the NetCDF file. Note that once the response size goes beyond the bufferSize, Tomcat will fallback to 'Transfer-Encoding: Chunked' (which we don't want). So make sure you're setting the buffer size to the correct value. Hope that helps! p.s. I cc'd this to the netcdf-java mailing list in case I got something wrong. Hopefully someone will correct me. Cheers -- B ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Brian Schlining MBARI Software Engineer, Research and Development brian@xxxxxxxxx <mailto:brian@xxxxxxxxx> (831) 775-1855 http://www.mbari.org/staff/brian-- Sincerely, Bob Simons IT Specialist Environmental Research Division NOAA Southwest Fisheries Science Center 1352 Lighthouse Ave Pacific Grove, CA 93950-2079 Phone: (831)658-3205 Fax: (831)648-8440 Email: bob.simons@xxxxxxxx <mailto:bob.simons@xxxxxxxx> The contents of this message are mine personally and do not necessarily reflect any position of the Government or the National Oceanic and Atmospheric Administration. <>< <>< <>< <>< <>< <>< <>< <>< <><_______________________________________________ netcdf-java mailing list netcdf-java@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
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