Example: Circuit Breaker

[tkohegyi]

Need example solution for creating CircuitBreaker with Wilma.

Purpose: When we use Wilma in microservice environment, we might want to use it to act as circuit-breaker too. However it is possible, it is not offered by Wilma by default. Offering a default solution of circuit-breaker would be nice.

The Approach and Description below is just an initial idea, might be changed during the actual implementation

Approach: monitor req-res pairs, and if there is a problem, or it is requested, forward requests to its stub for a certain time.

Description: Need interceptor that gets both request and response. Req interceptor: adds special header with circuit-breaker-ID Resp interceptor: evaluates if response is ok/not ok, and if not ok, turns on the circuit breaker Class name: CircuitBreaker Parameter list in XML:

• circuitBreakerID - unique name/id of the circuit breaker, will be added by req interceptor
• ServicePattern - pattern of target service url in order to identify the target service this circuitbreaker belongs to
• timeout - defines how long the circuit break should be active after turned on, in msec
• errorcodes - lit of Exxx codes when response should be considered as bad, and circuit breaker should be turned on - if empty nothing to do (response evaluation will be done externally)

Need API extension with:

• CircuitBreakerDescriptor[] getCircuitBreakerDescriptorList() - get all circuit breakers
• long (?) getCircuitBreakerStatus(CircuitBreakerDescriptor cb) - gets the remaining time (in msec) meanwhile the cbis turned on, or 0 if cbis off
• setCircuitBreakerStatus(CircuitBreakerDescriptor cb, long(?) timeout) - turns on cb, with timeout, or turns cb off if timout is 0 or less - this can be used when cb should be turned on/off from external party

What circuitbreaker ON would mean: enable all dialogdescriptors where the name contains the circuitBreakerID at the end of its name, with timeout.

[tkohegyi]

Branch "cb" is used to implement this.

[tkohegyi]

Done - see implemented solution and readme here: https://github.com/epam/Wilma/tree/master/wilma-extras/circuit.breaker