When I try to run a task with a small period (1 second or less) using ManagedScheduledExecutorService.scheduleAtFixedRate sometimes I get NullPointerException at http://grepcode.com/file/repo1.maven.org/maven2/org.wildfly/wildfly-ee/8.0.0.Final/org/jboss/as/ee/concurrent/ConcurrentContext.java line 167 (resetHandles is null). I think it occurs when a next task has run before a previous finishes. On 8.1.0 I have the same problem.