Makes a call to hello-service with a URI provided by the Service Registry for Pivotal Cloud Foundry, and uses a circuit breaker provided by the Circuit Breaker for Pivotal Cloud Foundry.
In this example, we'll need a blue-green deployment of hello-service. Please see the hello-service setup in hello-client-eureka to set this up.
If a Circuit Breaker called hystrix hasn't been set up in the space, you'll need to set one up. See the relevant docs section. Specifically:
- Use
hystrixas the name of the service instance.
Run mvn clean package && cf push to push the app as hello-client to the currently targeted space, using a random route
$ while true; do curl [the random route outputted by cf push]; done
You should see the value returned by either hello-service-blue ("Hello blue!") or hello-service-green ("Hello green!"), and this should switch on each invocation of curl. You can view the state of the calls to hello-service on the Circuit Breaker Dashboard.
Shut down hello-service-green with cf stop hello-service-green. In the Circuit Breaker Dashboard you'll see the error rate climb and the circuit open. In the curl output, you'll see Hello blue!hello... something?Hello blue!hello... something?... for a few seconds and then hello... something? continuously once the circuit is fully open. After about 30 seconds, hello-client-hystrix will re-fetch the list of live services from the Service Registry, and then stop attempting to make calls to hello-service-green since that will no longer be in the list. At this point, only sucessful calls will be made, and the circuit will close.
At no point is an error ever sent to curl; instead, the fallback response "hello... something?" is sent.
Try switching on/off hello-service-blue and hello-service-green, and switch both off, and see the behaviour of the Circuit Breaker Dashboard and curl output.