To get any numbers fpr “Data source metrics” you have to add statistics-enabled=“true” to your datasource definitions. See e.g. here: https://developer.jboss.org/thread/269809
This seems to indicate, that the network conection from Wildfly to the MySql was lost.
My guess is, that this is more a topic for the wildfly forum an not related to use of Camunda.
Do you run other applications using the same datasource on this wildfly server?