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Re: DODS AS
- Subject: Re: DODS AS
- Date: Tue, 09 Sep 2003 17:55:24 -0600
Joe McLean wrote:
Hi John,
I have tried to use an NcML file in the latest Agg Server
configuration I downloaded last Friday. I repeatedly receive a java
error from the server at http://stout.pmel.noaa.gov:8180/dodsC/
This is the pertinent snippet of the error:
java.lang.NullPointerException
at
dods.servers.agg.CatalogServlet.addAccess(CatalogServlet.java:611)
at
dods.servers.agg.CatalogServlet.readCatalog(CatalogServlet.java:257)
at dods.servers.agg.CatalogServlet.init(CatalogServlet.java:178)
at javax.servlet.GenericServlet.init(GenericServlet.java:258)
are you still getting this error? i cant reproduce it. I am seeing this
catalog:
<catalog name="Test NCML Aggregation" version="0.6">
<dataset name="Top-Level Dataset" dataType="Grid" serviceName="this">
<service name="this" serviceType="DODS" base=""/>
<service name="stdmet" serviceType="NetCDF"
base="file://WEB-INF/dodsAS/"/>
<dataset name="NDBC stdmet buoy data">
<property name="internalService" value="stdmet"/>
<dataset name="stdmetNcML Agg test" urlPath="TestNcML.xml"/>
</dataset>
</dataset>
</catalog>
with this external URL: http://stout.pmel.noaa.gov:8180/dodsC/TestNcML.xml
and this internal URL: file://WEB-INF/dodsAS/TestNcML.xml
this is a relative URL to the current path, so the absolute path is
apparently:
file:/usr/local/www/html/TOMCAT_DEMO/las/las_servlet/jakarta/webapps/dodsC/WEB-INF/dodsAS/TestNcML.xml
and i get the error message:
message = "CatalogServlet ERROR opening NcDataset TestNcML.xml
access =
file:/usr/local/www/html/TOMCAT_DEMO/las/las_servlet/jakarta/webapps/dodsC/WEB-INF/dodsAS/TestNcML.xml
Is this the correct path? is not, try using the absolute path in the "stdmet" service element.
absolute paths i think are system dependent; on linux try using 3 slashes or 1 slash:
<service name="stdmet" serviceType="NetCDF"
base="file:///path/something/WEB-INF/dodsAS/"/>
<service name="stdmet" serviceType="NetCDF"
base="file:/path/something/WEB-INF/dodsAS/"/>
I used your Catalog and NcML aggregation as templates (following this
message) and ctreated the following
Both are in $tomcat_root/dodsC/WEB-INF/dodsAS/ the web.xml file
points to the correct Catalog.xml file.
Any ideas? Is it that the NcML netcdf element can't handle a DODS
URL? AmI confused about where the aggregation should take place?
--------------------------------------
AggServTestCatalog.xml
---------------------------------------
<!DOCTYPE catalog SYSTEM
"http://www.unidata.ucar.edu/projects/THREDDS/xml/AggServerCatalog.dtd";>
<catalog name="Test NCML Aggregation" version="0.6"
xmlns="http://www.unidata.ucar.edu/thredds";
xmlns:xlink="http://www.w3.org/1999/xlink";>
<service name="this" serviceType="DODS" base=""/>
<service name="stdmet" serviceType="NetCDF"
base="file://WEB-INF/dodsAS/"/ <file://WEB-INF/dodsAS/>>
<dataset name="NDBC stdmet buoy data">
<property name="internalService" value="stdmet"/>
<dataset name="stdmet NcML Agg test"
urlPath="TestNcML.xml" />
</dataset>
</catalog>
-
<catalog name="Test NCML Aggregation" version="0.6">
-
<dataset name="Top-Level Dataset" dataType="Grid" serviceName="this">
<service name="this" serviceType="DODS" base=""/>
<service name="stdmet" serviceType="NetCDF" base="file://WEB-INF/dodsAS/"/>
-
<dataset name="NDBC stdmet buoy data">
<property name="internalService" value="stdmet"/>
<dataset name="stdmetNcML Agg test" urlPath="TestNcML.xml"/>
</dataset>
</dataset>
</catalog>
Also tried full path for service:
<service name="stdmet" serviceType="DODS"
base="file:///usr/local/www/html/TOMCAT_DEMO/las/las_servlet/jakarta/webapps/dodsC/WEB-INF/dodsAS/"/
<file:///usr/local/www/html/TOMCAT_DEMO/las/las_servlet/jakarta/webapps/dodsC/WEB-INF/dodsAS/>>
Also tried serviceType="NetCDF"
<service name="stdmet" serviceType="NetCDF"
---------------------------------------
TestNcML.xml
---------------------------------------
<?xml version='1.0' encoding='UTF-8'?>
<netcdf xmlns='http://www.ucar.edu/schemas/netcdf'
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xsi:schemaLocation='http://www.ucar.edu/schemas/netcdf
http://www.unidata.ucar.edu/schemas/netcdfDataset2.xsd' >
<variable name='recnum' type='int' shape='recnum' >
<attribute name='long_name' type='string' value='time coordinate' />
<attribute name='units' type='string' value='hours since
2001-09-31 00:00:00 UTC' />
<values start='0' increment='1' />
</variable>
<aggregation dimName='recnum' type='joinExisting' />
<netcdf
uri='http://dods.ndbc.noaa.gov/cgi-bin/nph-nc/dods/b42001_2001_09_stdmet.nc'/
<http://dods.ndbc.noaa.gov/cgi-bin/nph-nc/dods/b42001_2001_09_stdmet.nc%27/>>
<netcdf
uri='http://dods.ndbc.noaa.gov/cgi-bin/nph-nc/dods/b42001_2001_10_stdmet.nc'
/>
<netcdf
uri='http://dods.ndbc.noaa.gov/cgi-bin/nph-nc/dods/b42001_2001_11_stdmet.nc'/
<http://dods.ndbc.noaa.gov/cgi-bin/nph-nc/dods/b42001_2001_11_stdmet.nc%27/>>
</netcdf>
---------------------------------------
Joe
------------------------------------------------
John Caron wrote:
ok, you need to download a new dodsC.war file, follow instructions from
this page:
http://www.unidata.ucar.edu/projects/THREDDS/tech/aggServer/AggServerInstall.html
here is an example NcML aggregation that i tested on 3 of your files;
it assumes a uniform 10 minute increment to add a coordinate variable.
it does a join on the recnum dimension on the listed 3 files. it should
work for you, except that obviously you replace with your files, in time
order, and get the starting time right.
<?xml version='1.0' encoding='UTF-8'?>
<netcdf xmlns='http://www.ucar.edu/schemas/netcdf'
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xsi:schemaLocation='http://www.ucar.edu/schemas/netcdf
http://www.unidata.ucar.edu/schemas/netcdfDataset2.xsd' >
<variable name='recnum' type='int' shape='recnum' >
<attribute name='long_name' type='string' value='time coordinate' />
<attribute name='units' type='string' value='minutes since 2001-8-31
23:00:00 UTC' />
<values start='0' increment='10' />
</variable>
<aggregation dimName='recnum' type='joinExisting' />
<netcdf uri='C:/data/buoy/cwind1.nc'/>
<netcdf uri='C:/data/buoy/cwind2.nc' />
<netcdf uri='C:/data/buoy/cwind3.nc'/>
</netcdf>
the agg server configuration looks like this:
<!DOCTYPE catalog SYSTEM
"http://www.unidata.ucar.edu/projects/THREDDS/xml/AggServerCatalog.dtd";>
<catalog name="Test NCML Aggregation" version="0.6"
xmlns="http://www.unidata.ucar.edu/thredds";
xmlns:xlink="http://www.w3.org/1999/xlink";>
<service name="cwind" serviceType="NetCDF"
base="file:///c:/data/buoy/"/ <file:///c:/data/buoy/>>
<dataset name="cwind buoy data">
<property name="internalService" value="cwind"/>
<dataset name="cwind NcML Agg test"
urlPath="cwindAgg.xml" />
</dataset>
</catalog>
where the NcML file (as above) lives at
file:///c:/data/buoy/cwindAgg.xml
hopefully this will get you started, let me know how it goes.
BTW, this wont scale too huge numbers of netcdf files, but a few dozen
should be ok. i will need to add some file caching to speed it up, but
the above shoul be ok for small sets of files.