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Circuit Breaker

Circuit breakers are used to protect upstream servers by rejecting traffic to them when they become overwhelmed, allowing them time to recover back into a steady operational state. When the upstream server starts to fail requests at too high of a rate, the circuit is "opened".

The circuit breaker is an implementation of Netflix's Hystrix circuit breaker specification.

If the upstream server responds with more than the threshold percentage of requests with 5XX status codes, the circuit breaker preemptively reject all subsequent requests at the ngrok edge with a 503 until the upstream server's error rate drops below the threshold percentage.