Notifier

The Notifier implements the following state machine

The intended usage pattern is:

• there are goroutines, aka Producers, that append work to a queue pendingWorkQueue
• there is a number of goroutines, aka Consumers, that pull work from the pendingWorkQueue
  • they consume work until they have drained the pendingWorkQueue
  • when they find that the pendingWorkQueue contains no more work, they go back to the notifier and await notification

Note that the consumer / producer interact in a different order with the pendingWorkQueue vs the notifier:

• the producer first drops its work into the queue and subsequently sends the notification
• the consumer first processes elements from the queue and subsequently checks for a notification Thereby, it is guaranteed that at least one consumer routine will be notified when work is added