JMeter parallel requests with server-sent-events

Question

I've got a JMeter test where I'm currently using a loop to find out if some condition is true. Rather than polling, I would like to (and can) use a request on a resource that sends out server-sent-events (SSE). The way it should work, is that the SSE thread is started and than another thread is started which does a request that ultimately will cause a specific event to be sent. If that event is received processing should continue.

Maybe more clear graphically. My current script looks something like this:

ThreadGroup
 |
 + request 1
 + request 2
 ...
 + request N
 + Transaction controller
 |  |
 |  + While controller
 |     + polling request
 |
 + request N+1

I would like something like this

ThreadGroup
 | 
 + request 1
 + request 2
 ...
 + <help needed here>
 |  |
 |  + event thread
 |  |   + request SSE
 |  |       + onEvent x: y = true
 |  + action thread
 |     + request N
 |     + While y=false wait
 + request N+1

Is this possible? If so how? If not, can I create a sampler to do this? Any pointers?

Groeten,

Friso

Answer 1

I think you will have to implement your own class.

First, as a client of SSE, you should look at this:

• https://jersey.java.net/documentation/latest/sse.html#d0e11970

The second step is to implement a custom sampler that will extend this class:

• https://jmeter.apache.org/api/org/apache/jmeter/protocol/java/sampler/AbstractJavaSamplerClient.html

And use it with this GUI:

• http://jmeter.apache.org/usermanual/component_reference.html#Java_Request

Now for the most complex part (maybe we should create a github project to discuss this implementation and once finished contribute it to core JMeter project :-) ):

• The SSESampler sampler can work in 2 modes :
  • Block until it receives the response from server, this way you can assert on result
  • Start a thread (better use a pool of threads or Reactor pattern) to listen from server, once it gets the response, we have to find a way for the initial thread to be able to access this and assert. We could work with a thread safe Map shared and where data would be keyed by some data passed to the SSESampler

These are just initial ideas and need more work.