public ConcurrentMap<Thread, Runnable> getRunningTasks() {
      return running;
    }
@return a map of the threads currently running tasks inside this executor. Each key is an
        active thread, and the value is the task that is currently running. Note that this is
        not a stable snapshot of the map.
hbase-server/src/main/java/org/apache/hadoop/hbase/executor/ExecutorService.java