The Workflow Server provides the metric workflow.processes, which returns the number of open workflow processes, which are processes in state not started, running, or suspended. The tag definition can be used to filter by process definition name.

For example, you can request the number of StudioTwoStepPublication workflows with

http://localhost:40381/actuator/metrics/workflow.processes
  ?tag=definition:StudioTwoStepPublication

The response:

{
  "name": "workflow.processes",
  "description": "Number of open process instances",
  "baseUnit": "process instances",
  "measurements": [
    {
      "statistic": "VALUE",
      "value": 1
    }
  ],
  "availableTags": []
}