How can I test async callbacks in JMeter?

Question

I am using WebHooks in my API. So, once a request is processed our REST Service will POST a response back to the callback URL sent in the request.

Client             Server
  |(request)         |
  |----------------->|     
  |<-----------------|     ||
  |        (response)|     ||
  |                  |    _||_ Time
  |        (callback)|    \  /
  |<-----------------|     \/
  |----------------->|
  |(response)        |
  |                  |

How can this be stress tested with JMeter?

Answer 1

It depends on WebHook implementation, if it is a matter of polling - you can just use While Controller to wait for callback in loops. The whole duration of the sequence can be measured using i.e. Transaction Controller

If the callback comes a a Server-Sent Event you can use i.e. JAX RS API which provides SseEventSource class which can be used for waiting for server-side events either in JSR223 Sampler or in Java Request sampler like described in Stress/Load-Testing of Asynchronous HTTP/REST Services with JMeter article