Persistent and asynchronous stream for communication between appengine/Spring and front-end

Question

At the moment my website is using Spring that handles the http(s) request to and from the front-end like this:

@RestController
public class ComputeController {

    @RequestMapping(value = "/api/compute", method = RequestMethod.POST)
    public String compute(@RequestBody CodeToken code, OAuth2Authentication OAuth2) {
        Map<String, String> userInfo = UserInformation.getUserInfo(OAuth2);

        String sourceCode = code.getSource();
        String filename = code.getFilename();
        String email = userInfo.get("email");

        try {
            DataStorage dateStorage = new DataStorage();
            Compiler compiler = new Compiler(dateStorage);

            return compiler.compile(filename, sourceCode, email);
        } catch (Exception e) { // TODO Don't catch all exceptions
            return e.getStackTrace().toString();
        }
    }
}

The problem is that I need my front-end (built in Angular) to be able to receive and send information asynchronous from the http(s) request sent from the front-end. Like an continuous I/O stream from the server mid request while the "compiler.compile(...)" is running.

I presume I need to use sockets for this but I'm looking for suggestion on a good way to implement them.

Answer 1

If I understand your intention correctly, you're trying to display some progress in your client while the code compiles. You have two options:

1. As you proposed, use WebSockets. Spring supports them well. You can see an example here: https://github.com/AlexeySoshin/SpringWebSockets/tree/master/src/main/java/com/alexeysoshin/chat
2. Instead of blocking your response,
   1. Do compilation on a separate thread pool.
   2. Assign each compilation UUID when you submit this task.
   3. Return the client this task immediately.
   4. Poll another endpoint with UUID