How do i keep the JVM alive to receive connections...

# coroutines

[paulex]

How do i keep the JVM alive to receive connections.... e.g

fun main(args:Array<String>) = runBlocking<Unit>{
   InternalLoggerFactory.setDefaultFactory(Log4JLoggerFactory.INSTANCE)
   val server = AppServer(this)
   server.run()
}

I want to main thread to stay alive until a shutdown...

[Erik]

You could for example launch your coroutine from a CoroutineScope and join() the Job that launch returns before the JVM exits.

[elizarov]

What is AppServer ? You should check it out to see what facilities it provides to wait until shutdown.

[paulex]

@elizarov
AppServer has this method...

@Throws(InterruptedException::class)
fun blockUntilShutdown(){
    this.server.awaitTermination()
}

This is the implementation of awaitTermination

@Override
public void awaitTermination() throws InterruptedException {
    synchronized (lock) {
      while (!terminated) {
        lock.wait();
      }
    }
  }

[elizarov]

Then you don’t need coroutines (runBlocking) here. Just use this awaitTermination to block.

[paulex]

But for reason, when i use the awaitTermination provided by the grpcServer...

i can receive request on my grpcServer but for some reasons,

launch {} blocks are not triggered.

[elizarov]

You should launch { … } in some other dispatcher, because you’ve blocked your main thread by waiting, or block some other thread to wait for termination, and then you’ll be able to launch in your main thread.

[elizarov]

The former: launch(Dispatchers.Default) { … }
The latter: withContext(<http://Dispatchers.IO|Dispatchers.IO>) { server.blockUntilShutdown() }
Either way it should work.

[paulex]

Alright, thanks @elizarov, I'm going to try this out... Thanks very much..

[paulex]

@elizarov

So I did something like this, and it seems to work fine...

Class ServiceA (val scope: CoroutineScope){
   @Inject
   private val repo: Repository

   fun getFoo(id, callback){
      scope.launch {
		repo.getFooFromDatabase() //suspend function
      }//end of scope
	}//end of function
}//end of class

//Main Function
fun main(){
  val serviceA = ServiceA(CoroutineScope(Dispatchers.Default));
  …
  appServer.awaitTermination();
}

I'm guessing this is not a bad practice, the way i have initialized CoroutineScope.. Thanks in advance