title: Spring WebFlux (Flux): how to publish dynamically
body: <p>I am new to Reactive programming and Spring WebFlux. I want to make my App 1 publish Server Sent event through Flux and my App 2 listen on it continuously.</p>
  
  <p>I want Flux publish on-demand (e.g. when something happens). All the example I found is to use Flux.interval to periodically publish event, and there seems no way to append/modify the content in Flux once it is created.</p>
  
  <p>How can I achieve my goal? Or I am totally wrong conceptually.</p>