[idvusers] http based .nc retrieval issue in IDV 2.4

[Jeff McWhirter]

Hi Stuart,

> In the past I have used IDV to load and view data from a netcdf file  
> (CF-compliant) accessed over http (I use Tomcat as the web server, not  
> that that should matter).  this is NOT an opendap server in any way.
>
> Now, in IDV 2.4, this is failing.  I get this error:
>
> java.io.IOException: Server does not support byte Ranges
> 	
This is probably a http server configuration. To access netcdf files via 
http you need to have byte ranges turned on on your server:

http://www.unidata.ucar.edu/software/netcdf-java/reference/HTTPservice.html

As to the below opendap request that returns a 404 that is how the 
IDV/Java netcdf code works. It will first try to open the url as an 
opendap url
(the .dds). This fails with a 404. Then it tries it as a http. Perhaps 
you did not see that in your tcpmon output?

-Jeff


> at  
> ucar 
> .unidata.io.http.HTTPRandomAccessFile.<init>(HTTPRandomAccessFile.java: 
> 99)
> 	at  
> ucar 
> .unidata.io.http.HTTPRandomAccessFile.<init>(HTTPRandomAccessFile.java: 
> 78)
> 	at ucar.nc2.NetcdfFile.getRaf(NetcdfFile.java:283)
> 	at ucar.nc2.NetcdfFile.open(NetcdfFile.java:264)
> 	at ucar.nc2.dataset.NetcdfDataset.openFile(NetcdfDataset.java:335)
>
> For debug, I put tcpmon in between IDV and my web server.  When IDV  
> issues this request
>
> HEAD /uwme/netcdf/2007031700-gasp-d2.nc.dds HTTP/1.1
> User-Agent: Java/1.5.0_13
> Host: localhost:8080
> Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
> Connection: keep-alive
>
> it gets this response (since we have no .dds file nor servlet mapped  
> to service the url)
>
> HTTP/1.1 404 /uwme/netcdf/2007031700-gasp-d2.nc.dds
> Date: Mon, 17 Mar 2008 20:38:17 GMT
> Server: Apache/2.2.6 (Fedora)
> Connection: close
> Content-Type: text/html;charset=ISO-8859-1
>
> It appears as if the 404 response is throwing the IDV error.  Weird  
> thing is that there is no 'byte range' http header in the request??
>
> Looking at the stack trace above, maybe the issue lies in the netcdf- 
> java package, since IT contains the HttpRandomAccessFile class???
>
> Any help appreciated.
>
> PS: If I download a nc file from my web site using a browser and then  
> load that from local disk in IDV, the file loads OK.
>
>
> Stuart
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