You can ignore the kong_process_events being full. It is allocated to the full amount but is not in complete use. At least, that’s the case in most DB-less deployments.
Regarding the original problem, I’ve no clue of why Kong is trying to resolve the DNS name jenkins.ci.svc.
Can you make sure that the route -> service -> upstream -> target connections hold up correctly?
Meaning, the service <-> upstream connection is setup correctly?
The way those two are connected are by the host property of the service object should be same as the name property of the upstream object.