In Activiti, we have a need to control how jobs (serviceTasks) are executed. More specifically, we have some jobs that we want to limit to 2 concurrently, but other jobs may run 10 concurrently. All of these jobs are serviceTasks, no Timers or other async code. I have looked at the JobExecutor (and the Async version) but it seems to deal only with async code. How can I control this type of serviceTask execution?