refs: Services Heartbeat & Service Discovery

It has to do the following:

1. Know when service doesn't work ( Services Heartbeat )
2. Add / Close connection ( control the Service Discovery )

How it Works?

Closed

• when normally requests goes -> closed switch (allow requests)
• if requests above treshold (ex: 75% of requests fail in time window) -> open switch (disallow requests)

Open

• disallow requests (just deny - 500-599 Server Error)

Half Open

• After intervals, let x requests pass through & measure
• If most pass -> Closed (re-allow)
• if most still fail -> keep open (disallowed)