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CCT Open Interfaces SDK

Web Services and Mission Critical HA

General 1

Why Do We Need To Be Aware of This?. 2

Generate the WSDL binding every time. 2

Get notified of a switch over 3

Get notified of a switch over. 3

The Polling method. 3

via Notification. 4

 

General

AACC supports “High Availability” for fault tolerant and mission critical contact centers. The following levels of campus high availability are supported :

·        Mission Critical High Availability for SIP-enabled Contact Centers.

·        Hot-standby High availability for AML-based Contact Centers.

·        Warm standby High Availability.

For full details and definitions of these various levels, please refer to latest “Avaya Aura Contact Center Fundamentals and Planning” documentation.

For Mission Critical High Availability campus solutions web service sessions and notifications are seamlessly retained.  No further action is required on the client side. The user can register for the start/stopHASwitchEventListener so that they receive a courtesy notification of switchover if they so require. This feature is provided as part of the User Service. As this is a courtesy notification to indicate switchover no identifier information is passed back in the notification to the service user. It’s up to the service user to determine how they should handle this notification. See chapter 4 for further details

 

Hot Standby and Warm Standby campus solutions do not preserve Web services sessions during a switchover. Clients developed using this interface must be programmed to detect and respond to HA switchovers. It is not recommended that the customer use the start/stopHASwitchEventListener in this scenario as there is no guarantee given that they will receive the notification on/after switchover. For this scenario it is recommended that the customer uses the polling method described below.

 

Why Do We Need To Be Aware of This?

There is an unavoidable issue when dealing with Web Services and non-Mission Critical High Availability configured AACC. If a server goes down and a switch happens, the client’s 3rd party application will be unable to connect to the new server and will cease to function.

The reason for this is because when the WSDL bindings occur, the server fingerprint gets built into the generated XML web services client files. When a switch over happens, the server is switched and as a result we need to generate new XML web services client files.

For non-Mission Critical High Availability configured AACC, the client code that connects to the web services needs to have a process in place in case a server goes down and a switch happens.

We have two ways to approach this issue, we can:

Generate the WSDL binding every time     -           Has the potential for seamless transition but can be costly.

Get notified of a switch over                       -           More difficult to implement. (See Tutorial 3 A for general guidelines on event registration)

Generate the WSDL binding every time

The SOA OI Ref Client provides an example of how and when to generate WSDL’s every time we call a web service. Please refer to the src/Soa/client/com/Nortel/rc/dao/AddressServiceDOA.java file.

Get notified of a switch over

If you want to be notified of a switch over in a non-Mission Critical environment it is recommended that the Polling method is used. See next chapter for details.

 

 

Get notified of a switch over.

Two options are available to get notified of a HA switch over.

1.      The Polling method - This is the recommended method for non-Mission Critical High Availability systems.

2.      Via Notification – Although not critical for a Mission Critical High Availability solution, this feature is available so that clients will receive notification of switchover if required.

The Polling method

The User Service provides a method called sessionHartBeatAndHACheck(). When invoked, this method will return a SessionHartBeatAndHACheckResponse. The response will contain two Booleans, isSessionUpdated() and isHASwitchOver(). If isHASwitchOver() returns true, it means the server has switched and the client needs to generate new XML web services client files. Please refer to src.soa.client/com/Nortel/rc/dao/UserServiceDOA.java in the OI Ref Client and also the Tutorial 3 A tutorial to see how to register for specific events.

 

 

via Notification

The User Service provides you with a method called startHASwitchEventListener(). In the SOA OI Ref Client we register for notification using this method. Please refer to the src.soa.client/com/Nortel/rc/dao/UserServiceDOA.java file.

 

Here is sample code of a java implementation of the consumer service for the HA notification. Please refer to the src.soa.client/com/nortel/rc/event/HASwitchOverHandler.java file