如何在 vert.x 中执行断开连接的阻塞任务？

Question

I'd like use Vert.x to implement an asynchronous job executor.

In other words:

1. http request arrives
2. new thread is spawn to execute a long running blocking task
3. respond to the client (accepted request)
4. when the blocking task is completed, a http request is performed to inform the caller.

Is Vert.x the right choice for such logic?

Can you provide hints on how to implement this?

Answer 1

Vert.x main benefit is high concurrency. By their nature long running tasks are not concurrent, so you won't gain much benefit from using Vert.x

Anyway, Step 1 is your standard router.

final Router router = Router.router(this.vertx);
router.post("/jobs").handler(ctx -> {
   vertx.eventBus().send("jobsAddress", "some job data?");
   ...
});

Step 2 would be to launch worker verticles:

// In your main class
vertx.deployVerticle("your.worker.Verticle", new DeploymentOptions()
        .setWorkerPoolSize(20)
        .setWorker(true));

// In Worker class:
public class JobWorkerVerticle extends AbstractVerticle {

   @Override
   public void start() throws Exception {      
      vertx.eventBus().consumer("jobsAddress").handler(ctx -> {
          // Start your job
      });
   }
   ...
 }

Step 3 is again just standard router.

    router.post("/jobs").handler(ctx -> {
        ctx.response().setStatusCode(204).end();
    });

Finally, Step 4 is another route, GET this time:

router.get("/jobs/:id").handler(ctx -> {
   // Check if the job is completed or not yet
});

As an alternative, you can use WebSockets, and then respond with two types of messages: one for accepted job, and one for completed job.

The examples are with Vert.x 3.8, so if you're using Vert.x 4+, they'll probably have to be adapted a bit.