Smart Engine - Ability to pause/resume triggers to control incoming flow of events

[vijaynalawade]

Current behavior:
Today, engine will simply accept as many events as possible(Direct Runner) or block trigger go-routines when worker queue is full(Pooled Runner). This could lead to a performance issue or even loss of events due to resource constrains like CPU and Memory or blocked workers(Pooled runner). This might also lead to engine crash.
Expected behavior:
We need some policy based flow controllers who can control the incoming flow by temporarily pausing triggers and resuming them after certain low threshold is achieved.

What is the motivation / use case for changing the behavior?
This is useful in low resource environment like IoT.
Additional information you deem important (e.g. I need this tomorrow):