Configuring scoring services for high availability

You can configure the WML for z/OS scoring service for high availability. If you run multiple scoring services on a single LPAR or across different LPARs, you can achieve high availability by configuring your network TCP/IP with the SHAREPORT or DDVIPA option.

Before you begin

Review the Installation roadmap and make sure that you've completed all preceding tasks in the sequence, including Configuring WML for z/OS scoring services.
Consider configuring SHAREPORT for port sharing if your scoring servers reside on the same LPAR. With port sharing, all scoring servers use the same TCP port and all scoring requests are routed to the servers by using a weighted, round-robin distribution policy. This configuration ensures that online scoring service remains available even when some of the scoring servers are down.
Consider configuring DDVIPA (distributed dynamic VIPA) if your scoring servers run on different LPARs. A DDVIPA address and port also use a round-robin distribution policy to route requests to the scoring servers on separate LPARs. With DDVIPAs, online scoring service remains available even when some LPARs are lost.

Procedure

Customize and update the TCP/IP profile in the TCP communication layer of your network configuration.
- If your scoring servers run on the same LPAR, specify the SHAREPORT parameter on the PORT statement in the TCP/IP profile to enable port sharing, as shown in the following example.
```
PORT
 	11180 TCP SPARK*  SHAREPORT ;
```
  Where SPARK* is the user or user ID that starts the scoring process. A wildcard is allowed.
  
  All scoring servers on the same LPAR can now share and listen on the same port 11180 for scoring requests. For high availability, define each scoring server with a second but unique port, such as 11001, which is called the administrative port. The administrative port is required for processing deployment requests.
- If your scoring servers reside across different LPARs, define the VIPADYNAMIC block with the VIPADEFINE and VIPADISTRIBUTE keywords in the TCP/IP profile to enable DDVIPA for workload distribution. The VIPADISTRIBUTE keyword adds the required sysplex distributor definitions, which keeps all scoring services sysplex-aware.
```
VIPADYNAMIC                                                       
       VIPADEFINE <subnet_address> <ip_address> 
       VIPADISTRIBUTE DEFINE
               DISTMETHOD ROUNDROBIN <ip_address>                
               PORT 13330                               
               DESTIP ALL                             
ENDVIPADYNAMIC
```
  Where <ip_address> is the DDVIPA on port 13330.
  
  Consider specifying the VIPABACKUP keyword to automatically back up the LPAR where the DDVIPA option is defined. This configuration helps ensure that the scoring services are available when some LPARs are down.
```
VIPADYNAMIC                                                      
       VIPABACKUP 1 MOVE IMMED <subnet_address> <ip_address>
       VIPADISTRIBUTE DEFINE 
              DISTMETHOD ROUNDROBIN <ip_address> 
              PORT 13330 
              DESTIP ALL 
 ENDVIPADYNAMIC
```
See TCP/IP profile and configuration statements for more information about specifying the SHAREPORT or DDVIPA option.
Update the configuration of your scoring services, standalone or clustered, by using the administration dashboard.
See Adding a WML for z/OS scoring service to the administration dashboard for instructions on how to add or edit (update) a scoring service and see Configuring WML for z/OS scoring services for a list of commonly used parameters for configuring a scoring service.
- For a standalone scoring service, specify the following parameters:
  
  Service Name
  
  Specifies the name of the scoring service.
  
  Service Host
  
  Specifies the IP address or host name of the system where the scoring service runs.
  
  Service HTTP Port
  
  Specifies the HTTP port that the scoring service listens on.
  
  Service HTTPS Port
  
  Specifies the HTTPS port that the scoring service listens on.
- For a scoring service in a cluster, specify the following parameters:
  
  Service Name
  
  Specifies the name of an individual scoring service.
  
  Service Host
  
  Specifies the IP address or host name of the system where the scoring service runs.
  
  Service HTTP Port
  
  Specifies the HTTP port that the scoring service listens on, which must match the Cluster HTTP Port.
  
  Service HTTPS Port
  
  Specifies the HTTPS port that the scoring service listens on, which must match the Cluster HTTPS Port.
  
  Service Administrative HTTP Port
  
  Specifies the administrative HTTP port that all individual scoring services in a cluster and on the same LPAR listen on. This parameter is required when a scoring service instance is in a scoring cluster.
  
  Service Administrative HTTPS Port
  
  Specifies the administrative HTTPS port that all individual scoring services in a cluster and on the same LPAR listen on. This parameter is required when a scoring service instance is in a scoring cluster.
  
  Cluster Name
  
  Specifies the name of the scoring cluster.
  
  Cluster Host
  
  Specifies the IP address or host name of the system where the scoring cluster resides.
  
  Cluster HTTP Port
  
  Specifies the HTTP port that all the individual scoring services in the cluster listen on.
  
  Cluster HTTPS Port
  
  Specifies the HTTPS port that all the individual scoring services in the cluster listen on.