Grid Services with Service Data

Service Data is a structured collection of information that is associated to a Grid Service. This information must be easy to query, so Grid Services can be classified and indexed according to their characteristics.

An illustrative example is provided here. In this example, a Calculator Grid Service is created with additional Service Data. The Service Data includes details like version, author, last operation performed, etc.

Step 1: Creating the Grid Service from GWSDL

In order to create a Grid Service with Service Data, some changes are made to the .gwsdl file of the service.

First, two new namespaces are added: xmlns:data and xmlns:sd. The first corresponds to the Service Data Element type and the second namespace is an OGSI namespace which contains a set of service data-related tags.

Next, the schema file CalcDataType.xsd with the description of the new Data Type is imported. For example, in Calc.gwsdl, we describe CalcDataType.

Finally, we add a new tag named <sd:serviceData> inside the <gwsdl:portType> tag.

Next, an ant buildfile is used to create a Top Down Grid Service using this .gwsdl file. For example, build.xml is used to create the Calculator Service using Calc.gwsdl by executing the following command:
[purshah@danube mytry]$ ant createTopDownGridService

The corresponding output is shown in build_output.txt.

Step 2: Changes in the Implementation

Add whatever functionality is to be implemented within the operations of the Grid Service. And changes need to be made to the Grid Service Provider that implements OperationProvider and GridServiceCallBack. These changes are mainly with respect to Service Data.

For example, in CalcProvider.java, all the changes are marked with a comment // Added by Purvesh.

Step 3: Create a GAR

Create a Grid Service Archive (GAR) for the service.

For the Calculator Service, this is done using the command:
[purshah@danube mytry]$ ant topDownGar

The corresponding output is shown in gar_output.txt.

Step4: Deploy the Grid Service

In your GTK3.0 directory, use the command ant deploy -Dgar.name=<path to gar created in previous step> to deploy the Grid Service.

For example, the Calculator Service is deployed using the following command:
[purshah@danube test_install_dir]$ ant deploy -Dgar.name=/home/purshah/test_install_dir/mytry/servicedata/servicedataCalcService.gar

The corresponding output is shown in deploy_output.txt.

Step 5: Run the Grid Service

Once the service is deployed, start the container in GTK 3.0. This is done by using the command ant startContainer from the GTK 3.0 directory.

Then in another window, create an instance of the Grid Service using java org.globus.ogsa.client.CreateService <service-url> <id>. In this command, <service-url> is the Grid Service Handle (GSH) of the Grid Service Factory that must produce an instance of the Grid Service called <id>.

For example, an instance named calc is created when the following command is executed:
[purshah@danube test_install_dir]$ java org.globus.ogsa.client.CreatService http://localhost:8080/ogsa/services/services/Calc/CalcProviderFactoryService calc

The corresponding output was as follows:
Termination Time: infinity
Created service with reference:
<definitions name="CalcService" targetNamespace="http://Calc/service" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:calcservicebinding="http://Calc/bindings" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"><import location="http://156.56.104.61:8080/schema/services/Calc/Calc_bindings.wsdl" namespace="http://Calc/bindings"/><service name="CalcService" xmlns:gsdl="http://ogsa.globus.org/"><gsdl:instanceOf handle="http://156.56.104.61:8080/ogsa/services/services/Calc/CalcProviderFactoryService/calc" xmlns=""/><gsdl:instanceOf handle="http://156.56.104.61:8080/ogsa/services/instance" xmlns=""/><port binding="calcservicebinding:CalcServiceSOAPBinding" name="CalcServicePort"><soap:address location="http://156.56.104.61:8080/ogsa/services/services/Calc/CalcProviderFactoryService/calc"/></port></service></definitions

Step 6: Create and use Clients

A client must be created that can access the Service Data of the Grid Service.

For the Calculator Service, a client called CalcClient.java is written.

Now, compile and run CalcClient.java as follows:
[purshah@danube notification]$ javac client/CalcClient.java
[purshah@danube notification]$ java client.CalcClient http://localhost:8080/ogsa/services/services/Calc/CalcProviderFactoryService/calc

Then the following message should be displayed:
Version: 0.0
Author: purshah
Previous operation: NONE
# of operations: 0