PolicyObserver - Example

• Feature Overview
• Example Overview
• Working with the Example
• Sample Output

Feature Overview

This policy framework enables scalable administration of the Web NMS server and the network elements managed by it. The primary goal of the policy engine is to enable administration of complex functions easily. In Web NMS, policies can be used to customize the behaviour of the NMS and to provide a framework for adding policies for different network elements.

Web NMS policies can be broadly classified into two categories :

• Periodic Policies - Policies are triggered periodically by the server at the specified time interval. By default, the periodic policies are configured to be executed in the interval of 10 seconds.
• Non-periodic Policies - Policies are executed at the specified time. In this case, there is no fixed time interval. You need to specify the time at which the policy has to be executed. No default value is assigned for non-periodic policies.

Example Overview

You may require a notification whenever a policy is added, updated, deleted, executed or stopped from execution. This is possible by registering an observer with the policy engine.

Procedure to register as an observer

Two possibilities arise while registering as an observer :

Server and Client on

• the same JVM
• different JVMs

When the server and the client run on the same JVM, you use the static method getPolicyAPI() present under NmsClientUtil to get a NmsPolicyAPI handle.
 

com.adventnet.nms.db.NmsPolicyAPIapi=com.adventnet.nms.util.NmsClientUtil.getPolicyAPI();

Server and Client runing in different JVMs

When the server and the client run on different JVMs,  NmsPolicyAPI handle is obtained using RMI lookup
 

com.adventnet.nms.db.NmsPolicyAPIapi= (NmsPolicyAPI) Naming.lookup("//"+hostname+"//NmsPolicyAPI");

Once NmsPolicyAPI handle is got, you register an observer as follows.
 

api.register(Observer);

 

Note : You should take care of the number of TopoObservers as well as the amount of work done by the observers, which might cause performance issues.

For every change in Policy, each observer gets notified with a Properties Object comprising

• Action type
• Policy Name
• Policy Group Name and
• Current Status

intaction-integer.parseInt((String)prop.get("action"));

The following table lists the type of actions.
 

Action Type	Description
NmsPolicyAPI_POLICY_ADDED	This is for policy addition
NmsPolicyAPI.POLICY_UPDATED	This is for policy update
NmsPolicyAPI.POLICY_DELETED	This will be the action type when a policy gets deleted from the PolicyEngine
NmsPolicyAPI.POLICY_STOPPED	This will be the action type when a policy gets stopped
NmsPolicyAPI.POLICY_EXECUTED	This is for policy execution.

Policy Name

String Name= (String)prop.get("name");

Group Name

String GroupName = (String)prop.get("groupName");

Current Status

intcurrentStatus = Integer.parseInt((String)prop.get("currentStatus"));

The following table lists various status possibilities :
 

Status	Description
NmsPolicyAPI.POLICY_DISABLED	This will be the status, if the policy is in the diaabled state.
NmsPolicyAPI.POLICY_STOPPED	If the policy is not under execution, this will be the status.
NmsPolicyAPI.POLICY_SCHEDULED	This will be the status, when the policy is under Scheduled state
NmsPolicyAPI.POLICY_EXECUTED	When policy is executed, update to observers will be with this policy status.

If you require more properties about the policy, you can do so using NmsPolicyAPI.

Working with the Example

Classpath Settings

Set the CLASSPATH as <WebNMS  Home>\classes; <Web NMS Home>\ classes\AdventNetFramework.jar;

Compiling and Bundling with Web NMS

Compile it over the destination directory using the following syntax in the command prompt.

javac -d <Web NMS Home>/classes PolicyObserverExample.java.

javac -d <Web NMS Home>/classes ExecutePolicyObserverExample.java.

rmic -d <Web NMS Home>/classes test.PolicyObserverExample

Invoking the Example

If Web NMS is running in other hosts execute the following command :

java test.ExecutePolicyObserverExample -h <hostname> -p <RMI Port>

If Web NMS is running in localhost and the RMI registry is running in the default port 1099, no need for passing the arguments. The command for this case will be,

java test.ExecutePolicyObserverExample

Connecting the client

• Now connect to the client.
• Select 'policies' on the UI and right click it.
• From the pop-up menu select "AddPolicy" menu item.
• Now you can do any operation like add, update, execute or delete and you can get the notification

Sample Output

Upon doing any further operation like adding/deleting/executing/updating a policy, the following lines will be printed :

• Policy <name of the policy which underwent change> with the group Name - <Group Name> added/deleted/executed/updated
• <Status of the policy>