4 | Change Source |----->----+
9 | Change Source |----->----+
14 +-----------+ +-----------+
15 | Scheduler | | Scheduler |
16 +-----------+ +-----------+
18 +------+---------+ +---+ +-----+
25 +======+ +======+ : v :
28 +---------+ +---------+ :queue :
29 | Builder | | Builder | +======+
30 +---------+ +---------+ |