VNA not starting properly and the web UI REST page is unavailable

Products

• Virtual Network Assurance
• Network Observability

Issue/Introduction

After system reboots for OS patching, VNA is not starting properly.
We have the Spectrum integration disabled presently, but it's showing down in Netops Portal, and the rest page is unavailable. 

I've tried stopping / restarting wildfly and mysql, as well as rebooting the system, but still a no go. 

The environment is our lab, though we need to determine whether its related to the OS patching prior to patching in production. 

• DX NetOps Virtual Network Assurance (VNA) Gateway shows Operational Status as Down.
• VNA web UI at VNA_HOST:8080 returns a 404 page not found error.
• The MySql and Wildfly services at the OS level start and remain running, but there are errors in the server.log.
  • The server.log for the VNA host shows this error at the end of it's startup cycle:

Caused by: java.lang.UnsupportedClassVersionError: Failed to link com/ca/oc/ejb/engine/EngineManager (Module "deployment.oc-22.2.7-RELEASE.ear.oc-ejb-22.2.7-RELEASE.jar" from Service Module Loader): com/ca/oc/ejb/engine/EngineManager has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

Environment

All supported DX NetOps Virtual Network Assurance 21.2.9+ releases

All supported DX NetOps Virtual Network Assurance 22.2.x releases

Cause

System patching cycle removed the required Java 11 install leaving only the unsupported Java 1.8 release.

Resolution

Install Java 11 as the system java version and restart Wildfly.

Additional Information

• What version of java is in use?
  • Run the command "which java" to determine the java executable used by the OS.
  • Run "<path> java -version" using the path output from the which command.
  • A common output from the which command is /bin/java. We'd then run "/bin/java -version".
• How to tell the system to use Java 11 vs Java 8 if both are installed?
  • For RH we'd use the alternatives command.
    • Running "alternatives --config java" will allow specification of the java version the system should use.
• Additional information can be found on the How to install Java 8 and 11 on Red Hat Enterprise Linux 8 page on the RedHat Developers website.