Difference between revisions of "Thredds"

Revision as of 12:17, 4 February 2009

Thredds (Thematic Realtime Environmental Distributed Data Services) is a tomcat servlet that serves xml catalogs of openDAP datasets.

Setup

A working tomcat server is a prerequisite. Simply copy the thredds.war file obtained from the thredds homepage into the tomcat webapps directory.

data.mohid.com

• How do I restart the tomcat and thredds server in data.mohid.com?

> cd /home/guillaume/Software/las7/tomcat/tomcat/bin
> ./Tomcat5.sh start

• How do I know if tomcat is running?:

> netstat -tlnap | grep 8080

VmMrtSrv06

• 192.168.20.136 when it is resident on the LAN.
• To configure the tomcat to start during boot:

> sudo vim /etc/rc.d/rc.local
rc.local> /home/user/Download/apache-tomcat-6.0.18/bin/startup.sh

Catalogs architecture

We propose the following architecture as a good practice for maintaining catalogs.

Directory tree structure

$TOMCAT_HOME/content/thredds

• catalog.xml: catalog file containing links to all the subcatalogs containing the netcdf data.
  • pcomsCatalog.xml: catalog file pointed by the main catalog.

#catalog.xml
<?xml version="1.0" encoding="UTF-8"?>
<catalog name="THREDDS Server Default Catalog : You must change this to fit your server!"
       xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0"
       xmlns:xlink="http://www.w3.org/1999/xlink">

 <service name="thisDODS" serviceType="OpenDAP" base="/thredds/dodsC/" />
 <datasetRoot path="test" location="content/testdata/"/>

 <dataset name="Test Single Dataset" ID="testDataset" serviceName="thisDODS"
          urlPath="test/testData.nc"/>

 <datasetScan name="Test all files in a directory" ID="testDatasetScan"
              path="testAll" location="content/testdata">

   <metadata inherited="true">
     <serviceName>thisDODS</serviceName>
   </metadata>

   <filter>
     <include wildcard="*.nc"/>
   </filter>

 </datasetScan>

 <catalogRef xlink:title="Test Enhanced Catalog" xlink:href="enhancedCatalog.xml" name=""/>

 <catalogRef xlink:title="PCOMS Catalog" xlink:href="/opendap/pcoms/pcomsCatalog.xml" name=""/>

</catalog>

Building thredds urls

Dataset

• Viewing a ${catalog} file tree named ${catalog}.xml:

http://data.mohid.com:8080/thredds/${catalog}.html

• Viewing a specific ${dataset} thredds metadata:

http://data.mohid.com:8080/thredds/${catalog}.html?dataset=${dataset.id}

• Viewing a specific ${dataset}:

http://data.mohid.com:8080/${dataset.service.base}/${dataset.urlpath}

DatasetScan

• Viewing a particular ${datasetscan} tree from any ${catalog} in the thredds server:

http://data.mohid.com:8080/thredds/catalog/${datasetscan.path}/catalog.html

• Viewing a specific ${datasetscan.filteredfilename} thredds metadata:

http://data.mohid.com:8080/thredds/catalog/${datasetscan.path}/catalog.html?dataset=${datasetscan.id}/${datasetscan.filteredfilename}.nc.html

• Viewing a specific ${datasetscan.filteredfilename} dataset:

http://data.mohid.com:8080/${datasetscan.service.base}/${datasetscan.path}/${datasetscan.filteredfilename}.nc.html

A sample catalog file

[XML]

<?xml version="1.0" encoding="UTF-8"?>

<catalog name="MOHID THREDDS Server Catalog"
       xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0"
       xmlns:xlink="http://www.w3.org/1999/xlink">

 <service name="MOHID DODS" serviceType="OpenDAP" base="/thredds/dodsC/" />
 <datasetRoot path="test" location="content/testdata/"/>

 <dataset name="Test Single Dataset" ID="testDataset" serviceName="MOHID DODS"
          urlPath="test/testData.nc"/>

 <datasetScan name="Test all files in a directory" ID="testDatasetScan"
              path="testAll" location="content/testdata">

   <metadata inherited="true">
     <serviceName>MOHID DODS</serviceName>
   </metadata>

   <filter>
     <include wildcard="*.nc"/>
   </filter>

 </datasetScan>

 <catalogRef xlink:title="Test Enhanced Catalog" xlink:href="enhancedCatalog.xml" name=""/>

</catalog>

See also

• Tomcat
• OpenDAP
• LAS

External references

• Getting started
• MOHID Thredds data server