The circuitBreaker event handler

The circuit breaker is a pattern that helps preventing cascading failures in a system. The circuit breaker pattern allows you to build a fault-tolerant and resilient system that can survive gracefully when key services are either unavailable or have high latency.

It is implemented as a stateful software component that switches between three states:

closed - requests can flow freely
open - requests are rejected without being submitted to the remote resource
half-open - one probe request is allowed to decide whether to close the circuit again

You can provide your own custom global CircuitBreakerConfig. In order to create a custom global CircuitBreakerConfig, you can use the CircuitBreakerConfig.builder() method. Using the builder, you can configure the following properties.

Parameter	Default value	Description
`type`	`circuitBreaker`	The type is always `circuitBreaker`
`automaticTransitionFromOpen` `ToHalfOpenEnabled`	`false`	If set to `true` it means that the CircuitBreaker automatically transitions from open to half-open state and no call is needed to trigger the transition. A thread is created to monitor all the instances of CircuitBreakers to transition them to HALF_OPEN once waitDurationInOpenState passes. Whereas, if set to false the transition to HALF_OPEN only happens if a call is made, even after waitDurationInOpenState is passed. The advantage here is no thread monitors the state of all CircuitBreakers.
`failureRateThreshold`	50%	Configures the failure rate threshold in percentage. When the failure rate is equal or greater than the threshold the CircuitBreaker transitions to open and starts short-circuiting calls.
`minimumNumberOfCalls`	100	Configures the minimum number of calls which are required (per sliding window period) before the CircuitBreaker can calculate the error rate or slow call rate. For example, if minimumNumberOfCalls is 10, then at least 10 calls must be recorded, before the failure rate can be calculated. If only 9 calls have been recorded the CircuitBreaker does not transition to open even if all 9 calls have failed.
`name`	`GW_CIRCUITBREAKER`	The `circuitBreaker` name. It is used to create or retrieve the circuit breaker instance.
`permittedNumberOfCalls` `InHalfOpenState`	10	Configures the number of permitted calls when the CircuitBreaker is in `HALF_OPEN` state.
`slidingWindowType`	`COUNT_BASED`	If the sliding window is COUNT_BASED, the last `slidingWindowSize` calls are recorded and aggregated. If the sliding window is TIME_BASED, the calls of the last `slidingWindowSize` seconds recorded and aggregated.To determine the count type, default is `COUNT_BASED`, alternative is `TIME_BASED`
`slowCallDurationThreshold`	60000 ms	Configures the duration threshold above which calls are considered as slow and increase the rate of slow calls.
`slowCallRateThreshold`	50	Configures a threshold in percentage. The CircuitBreaker considers a call as slow when the call duration is greater than `slowCallDurationThreshold`. When the percentage of slow calls is equal or greater the threshold, the `CircuitBreaker` transitions to open and starts short-circuiting calls.
`writableStackTraceEnabled`	`true`	Enables writing the stack trace.
`waitIntervalFunctionIn` `OpenStateSupplierClass`		A functional supplier class. When passed a map, it returns an object that implements `IntervalFunction`.
`recordExceptionSupplierClass`		A functional supplier class. When passed a map, it returns an object that implements `Predicate<Throwable>`.
`properties`		The map that is passed to the above supplier. The presentation in JSON looks like `"properties":{ "key1":"value", "key2":"value"})`.