Transcript slidesA2

Assignment 2
“Simple” Grid Services
Assignment
Mark Holliday and Barry Wilkinson, 2004
A2.1
Grid Services Exercise
Preliminaries
Web services are stateless, whereas Grid services
can be either stateful or stateless, and transient or
persistent.
Grid services also use a factory service to
manufacture instances.
Mark Holliday and Barry Wilkinson, 2004
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Goals
• Build on the Web Services assignment.
• Show how Grid services differ from Web
services.
• Show how to create a stateful Grid service using
Globus 3.2 (GT3.2)
Mark Holliday and Barry Wilkinson, 2004
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Purpose of Grid Service
To store an integer value which can be acted
upon by methods to:
• Get its value
• Increment its value (add one), and
• Decrement its value (subtract one).
These methods are given. Further methods
will be implemented. The service is stateful
(the value is retained between accesses).
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ant
(Another Neat Tool)
• A build tool used in this assignment for
deploying service.
• Uses XML configuration files.
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Steps
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Preliminary set-up.
Define the Grid Service Using Java
Define the Grid Service Interface using GWSDL
Write the Deployment Descriptor
Build the Math Service
Deploy the Math Service using ANT
Write and Compile the Client
Start the Grid Service
Execute the Client
Add Functionality to the Grid Service
Mark Holliday and Barry Wilkinson, 2004
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Step 1: Set-up
• GT3.2 not set up for a multi-developer
environment.
• ant uses a common build directory for the
deployment of all services
– All users added to a common “globus” group
– Users need to create unique service names
– Users need to revise subdirectory structure of
services in user’s home directory
We wrote NameChangeScript to do this.
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Step 2: Define/Implement Grid
Service Using Java
// package and import statements not shown
public class MathImpl extends GridServiceImpl
implements MathPortType {
private int value = 0;
public MathImpl() {
super(“Math Factory Service”);
}
public void add(int a) throws RemoteException {
value = value + a;
}
public void subtract(int a) throws
RemoteException {
value = value - a;
}
public int getValue() throws RemoteException {
return value;
}
}
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Step 2 (continued)
This service is stateful. The value can be modified
via add or subtract, and accessed via getValue.
Service implemented in Java. Code provided in:
yourusernameAssignments/services/
MathService/impl/MathImpl.java
which is in the directory
/home/yourusername/GridServices/
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Step 3: Define Grid Service Interface
using GWSDL
The service interface is defined in GWSDL and
provided in:
schema/yourusernameAssignments/
MathService/impl/Math.gwsdl
which is in the directory:
/home/yourusername/GridServices/
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Step 3 (continued)
The GWSDL (Grid Web Services Description
Language) file specifies the namespace being
used:
http://www.globus.org/namespaces/
yourusernameAssignments/MathService
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Step 4: Writing Deployment Descriptor
Code for deployment descriptor for service provided
in
yourusernameAssignments/services/
MathService/server-deploy.wsdd
which is in the directory
/home/yourusername/GridServices/
Two key sections of deployment descriptor specify
the Math Service and the Math Service Factory.
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Step 5: Building the Math Service
Use the build script build.sh which specifies path to
your service and path to GWSDL file for the service.
[yourusername@terra GridServices] $ ./build.sh
yourusernameAssignments/services/MathService
schema/yourusernameAssignments/MathService/Math.gwsdl
A directory named build is created that contains all
the stub files, class files, and the GAR file.
The GAR file contains the java class files, GWSDL
files, compiled stubs, and the deployment descriptor
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Step 5 continued: Deploy Grid
Service using ant
ANT is a build program similar to the make program
but the dependencies are specified using xml.
Command line from globus directory:
[yourusername@terra globus] ant deploy -Dgar.name
=/home/yourusername/GridServices/build/lib/yourusername
Assignments_services_MathService.gar
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Step 6: Write and Compile Client
public class MathClient {
public static void main(String[] args) {
try { // Get command-line arguments
URL GSH = new java.net.URL(args[0]);
int a = Integer.parseInt(args[1]);
// Get a reference to the MathService instance
MathServiceGridLocator myServiceLocator =
new MathServiceGridLocator();
MathPortType myprog = myServiceLocator.getMathService(GSH);
// Call remote method 'add'
myprog.add(a);
System.out.println("Added " + a);
// Get current value through remote method 'getValue'
int value = myprog.getValue();
System.out.println("Current value: " + value);
} catch(Exception e) {
System.out.println("ERROR!");
e.printStackTrace(); }
}
}
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Step 6 (continued)
The code for the client is provided in:
yourusernameAssignments/clients/
MathService/Client.java
which is in the directory
/home/yourusername/GridServices
Compile it using javac.
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Step 7: Start Grid Service
Start globus container on a TCP port not in use.
From GridServices directory:
globus-start-container -p 8081
This example assumes port 8081 is not in use; use
netstat –t –all to see which ports are in use.
MathService and MathServiceFactory will be listed
as two of the services that are available once the
container has started.
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Step 8: Execute Client
Execute client. From GridServices directory:
java –classpath ./build/classes/:$CLASSPATH
yourusernameAssignments.clients.MathService.Client
http://152.30.5.102:8081/ogsa/services/yourusernameAssi
gnments/MathService 5
You will see the following result:
Added 5 Current value: 5
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Step 9: Extend Functionality of
Service
Add a multiply method to your Math Service.
Repeat all the steps to test it.
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Acknowledgment
This assignment and slides are derived from:
“Classroom Exercises for Grid Services”
by A. Apon, J. Mache, Y. Yara, and K. Landrus,
Proc. 5th Int. Conference on Linux Clusters: The
HPC Revolution, May 2004.
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