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Developing Router Initialization Scripts

When the SAE establishes a connection with a router, it can run a router initialization script to customize the setup of the connection. Router initialization scripts are run when the connection between a router and the SAE is established and again when the connection is dropped.

For JUNOSe VRs that supply IP addresses from a local pool, a router initialization script is provided that identifies which VR supplies each IP pool and writes the information to the configuration. The SAE runs the script only when a COPS connection is established to the JUNOSe router. Consequently, if you modify information about IP pools on a VR after the COPS connection is established, the SAE will not automatically register the changes, and you must update the configuration.

Table 7 describes the router initialization scripts that we provide with the SRC software in the /opt/UMC/sae/lib folder.




Table 7: Router Initialization Scripts 
Script Name
Function
When to Use Script

iorPublisher

Publishes the IOR of the SAE into an internal part of the shared configuration so that a NIC can associate a router with an SAE.

Use with JUNOSe routers that do not supply IP addresses from local pools, and with JUNOS routing platforms.

poolPublisher

Publishes the IOR of the SAE and local IP address pools in the directory so that a NIC can associate a router with an SAE and resolve the IP-to-SAE mapping.

Use with JUNOSe virtual routers that supply IP addresses from local pools.

Interface Object Fields

Router initialization scripts are written in the Python programming language (www.python.org) and executed in the Jython environment (www.jython.org).

Router initialization scripts interact with the SAE through an interface object called Ssp. The SAE exports a number of fields through the interface object to the script and expects the script to provide the entry point to the SAE.

Table 8 describes the fields that the SAE exports.




Table 8: Exported Fields  
Ssp Attribute
Description

Ssp.properties

System properties object (class: java.util.Properties)—The properties should be treated as read-only by the script.

Ssp.errorLog

Error logger—Use the SsperrorLog.printIn (message) to send error messages to the log.

Ssp.infoLog

Info logger—Use the Ssp.infoLog.printIn (message) to send informational messages to the log.

Ssp.debugLog

Debug logger—Use the Ssp.debugLog.printIn (message) to send debug messages to the log.

The router initialization script must set the field Ssp.routerInit to a factory function that instantiates a router initialization object:

The factory function must implement the following interface:

Ssp.routerInit(VRName,
virtualIp,
realIp,
VRIp,
transportVR)

The factory function returns an interface object that is used to set up and tear down a connection for a given COPS server. A common case of a factory function is the constructor of a class.

The factory function is called directly after a COPS server connection is established. In case of problems, an exception should be raised that leads to the termination of the COPS connection.

Required Methods

Instances of the interface object must implement the following methods:

Example: Router Initialization Script

The following script defines a router initialization class named SillyRouterInit. The interface class does not implement any useful functionality. The interface class just writes messages to the infoLog when the router connection is created or terminated.

class SillyRouterInit:
    def __init__(self, vrName, virtualIp, realIp, vrIp, transportVr):
        """ initialize router initialization object """
        self.vrName = vrName
        Ssp.infoLog.printin("SillyRouterInit created")

    def setup(self):
        """ initialize connection to router """
        Ssp.infoLog.printin("Setup connection to VR %(vrName)s" % 
                    vars(self))

    def shutdown(self):
        """ shutdown connection to router """
        Ssp.infoLog.printin("Shutdown connection to VR %(vrName)s" % 
                    vars(self))

#
# publish interface object to Ssp core
#
Ssp.routerInit = SillyRouterInit

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