ScheduledExecutorService.scheduleAtFixedRate - reentrant?

Question

By way of some library, I find myself calling this function twice concurrently on a single instance (using the implementation returned by Executors.newSingleThreadScheduledExecutor). The Runnable passed to the second call seems not to execute, neither immediately nor on the next scheduled slot, and no exception is raised. If I serialize the two calls (did this very crudely and unintentionally by putting a breakpoint before the second caller's scheduling call), then the second runnable is executed with no issue.

I'm new to this interface, but it doesn't seem like these scheduling functions are designed to be reentrant. But I can't find anything in the various documentation describing what should happen here.

Answer 1

Well, small test case doesn't reproduce the problem, so I have no reason to believe the function isn't reentrant. What actually fixed the problem was to remove all this from request time to server start. There were some other signs, like the breakpoint temporary fix I mentioned in the OP, that point to some awful timing issue, somewhere in my stack.