503 Service Unavailable for open circuit breaker

Detailed Description

Translate Failsafe’s CircuitBreakerOpenException into a probem response with a 503 Service Unavailable status.

Context

A CircuitBreakerOpenException that bubbles all the way up the web layer of an application can technically safely translated into a service unavailable response, since clients may be able to honor this.

Possible Implementation

• Optional dependency to Failsafe 2.0
  • Make sure it’s really optional at runtime
• Translate to 503 Service Unavailable
• No special problem type needed
• Optionally, set Retry-After header based on CircuitBreaker#getDelay

[whiskeysierra]

but it prevents due to previous timeout

That’s the most dominant type, yes. But circuit breakers can be opened for numerous other reasons, doesn’t have to be timeouts.

your service that is unavailable but in fact you’re are (or maybe partially)

Not really. If a CircuitBreakerOpenException bubbles up all the way from an HTTP Client/Gateway to a Resource/Controller (vocabulary stolen from https://martinfowler.com/articles/microservice-testing/#anatomy-modules) then this service is not available, since there was no fallback of any kind which makes this particular dependency a critical one.

So my reasoning for 503 Service Unavailable is the following:

This service is really not available since (at least) one critical dependency is not available.

[whiskeysierra]

Failsafe 2.1.1 adds support for retrieving the delay configuration: https://github.com/jhalterman/failsafe/blob/master/CHANGES.md#211