The callable queue service queues {@link XCallable}s for asynchronous execution.
Callables can be queued for immediate execution or for delayed execution (some time in the future).
Callables are consumed from the queue for execution based on their priority.
When the queues (for immediate execution and for delayed execution) are full, the callable queue service stops queuing callables.
A thread-pool is used to execute the callables asynchronously.
The following configuration parameters control the callable queue service:
{@link #CONF_QUEUE_SIZE} size of the immediate execution queue. Defaulf value is 10000.
{@link #CONF_THREADS} number of threads in the thread-pool used for asynchronous command execution. When this numberof threads is reached, commands remain the queue until threads become available. Sets up a priority queue for the execution of Commands via a ThreadPool. Sets up a Delayed Queue to handle actions which will be ready for execution sometime in the future.