One of the customer is using an Email Application which initiates outbound call using standard pdcobcall-07.10.12.02.jar library.
They would like to know – how this library getNextServerFromZone defines which server to use? As they had noticed the app configured on Prod EPM was also showing IP of a test EPM when trying to get the EPM server from zone intermittently. Issue was resolved after restart of app server.

This is a trace of a good scenario:
23/01/2020 03:45:39:112 INFO - 5387F0C266EF473595D76E0E622FA32E:/VPN_email_starter : Executing IPluggableExecutable com.avaya.sce.pdc.pe.launchobcall : Launching vxml outbound call to ->VPNRinging: with toURI:message:subject
23/01/2020 03:45:39:112 DEBUG - 5387F0C266EF473595D76E0E622FA32E:/VPN_email_starter : getNextServerFromZone: One server in zone:0 found, returning server:10.xxx.xx.34
23/01/2020 03:45:39:112 DEBUG - 5387F0C266EF473595D76E0E622FA32E:/VPN_email_starter : VPService: invoking webservice: https://10.10.18.34/axis2/services/VPAppIntfService
23/01/2020 03:45:39:118 DEBUG - 5387F0C266EF473595D76E0E622FA32E:/VPN_email_starter : VPService: secure connection complete
23/01/2020 03:45:39:118 DEBUG - 5387F0C266EF473595D76E0E622FA32E:/VPN_email_starter : LaunchVXML call to webservice with following arguments: appname:VPNRinging applurl:http://hq-avaya-app1:7080/VPNRinging/Start touri:989149736349 parameters: uui:1579740107 zone:

This is a bad case:

23/01/2020 23:45:54:093 INFO - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : Executing IPluggableExecutable com.avaya.sce.pdc.pe.launchobcall : Launching vxml outbound call to ->VPNRinging: with toURI:message:subject
23/01/2020 23:45:54:093 DEBUG - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : getNextServerFromZone: One server in zone:0 found, returning server:10.xxx.xx.131
23/01/2020 23:45:54:093 DEBUG - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : VPService: invoking webservice: https://10.10.18.131/axis2/services/VPAppIntfService
23/01/2020 23:45:54:099 DEBUG - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : VPService: secure connection complete
23/01/2020 23:45:54:099 DEBUG - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : LaunchVXML call to webservice with following arguments: appname:VPNRinging applurl:http://hq-avaya-app1:7080/VPNRinging/Start touri:989046605469 parameters: uui:1579812167 zone:
23/01/2020 23:45:55:166 ERROR - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : LaunchVXML error:Transport error: 401 Error: Unauthorized
23/01/2020 23:45:55:166 INFO - 5B3EE28BFE670C73CFE8B16C119988E2:/VPN_email_starter : Completed IPluggableExecutable com.avaya.sce.pdc.pe.launchobcall

The address 10.xxx.xx.34 is a product EPM server. The address 10.xxx.xx.131 is a test server.

Hi Dev Connect team,

Any inputs on the library query posted.
Appreciate your response. Thanks.

The getNextServerFromZone call is not a problem here. You only have one zone and one server which is passed to the method. The zone id and zone servers are so called platform/global parameters that get passed into the the app server via the URL request (by which EPM launches the app). These parameters are cached at the first call after the app server is started. The cache only get updated when the datetime stamp has changed. So it seems like here during the operation, the app server has not detected the change of the datetime stamp. It is EPM's responsibility to send the datetime stamp change when any of the global parameter has changed. You can observe the OD logs at the beginning of each call for any change of the parameters and datetime stamp change.

Thanks Wilson for the inputs.