...
Now, assuming that back-end services are up and running, the back-end can serve user’s requests. So let’s see what actually happens with a request to list all available markets. First, the request (GET /markets) is received by the HTTP server running at gateway node. The incoming request is simply passed from the HTTP server to the Gateway service that does all the processing and mapping. In this case in particular, the user's request is mapped into a “list all markets“-action of the Markets service. Next, the request is passed to the broker, which checks whether the Markets service is a local or a remote service. In this case, the Markets service is remote so the broker needs to use the transporter module to deliver the request.
The transporter simply grabs the request and sends it through the communication bus. Since all nodes are connected to the same communication bus (Message broker), the request is successfully delivered to the Markets service node. Upon reception, the Service broker of Markets service node will parse the incoming request and forward it to the Markets service. Finally, the Markets service invokes the action a-la list of all markets and returns the list of all available markets. The response is simply forwarded back to the end-user.
...