code: public boolean markSlotActive(AllocationID allocationId) throws SlotNotFoundException {
  		checkInit();
  
  		TaskSlot taskSlot = getTaskSlot(allocationId);
  
  		if (taskSlot != null) {
  			if (taskSlot.markActive()) {
  				// unregister a potential timeout
  				LOG.info("Activate slot {}.", allocationId);
  
  				timerService.unregisterTimeout(allocationId);
  
  				return true;
  			} else {
  				return false;
  			}
  		} else {
  			throw new SlotNotFoundException(allocationId);
  		}
  	}
docs: Marks the slot under the given allocation id as active. If the slot could not be found, then
  a {@link SlotNotFoundException} is thrown.
  
  @param allocationId to identify the task slot to mark as active
  @throws SlotNotFoundException if the slot could not be found for the given allocation id
  @return True if the slot could be marked active; otherwise false