The EJB TimerService might work depending on if your requirements are truly periodic. The timer service can fire off a stateless session bean method.
If it were me, I probably would write a JCA resource adapter. This is one place where you can create threads or use the Work Manager to manage the threads for you. To communicate back to the standard JEE components, you could use an inbound connection to drive a message driven bean endpoint. The MDB has full capabilities of interacting with other resources like a database, calling other EJB's, etc.
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