Scala main class with futures not terminating

Question

I have a scala main class

object Job extends App {

         def myProcedure() = {
             sqlu"""CALL `dbName`.`update_history();"""
         }

         implicit val system: ActorSystem = ActorSystem()
         implicit val mat: ActorMaterializer = ActorMaterializer()
         implicit val ec = system.dispatcher
         implicit val session: SlickSession = SlickSession.forConfig("my-mysql")
         val proc = session.db.run(myProcedure))
          
         val terminatedF = proc.flatMap { rec =>
              println("value of the procedure ::" + rec)
              session.close()
              system.terminate()
         }
         Await.result(terminatedF, Duration.Inf)
          println("terminated :::")
     }

I see that the value of rec gets printed, and also terminated ::: i.e. last line also gets printed. However the program does not end. Am I missing anything here ?

You probably need to "close" or "terminate" that session somehow. I don't know slick, but this snippet doesn't look write to me, leaving the `session` thing just sitting around like this. That's not how code accessing external resources usually looks. To your question, it probably has a thread pool inside, that prevents your program from exiting. Try sifting through slick documentation looking for session management specifically. — Dima, Jul 01 '21 at 11:42
Thanks for replying, however I figured out the problem. It had nothing to do with slick but had something to do to make JVM exit gracefully — user9920500, Jul 17 '21 at 14:44
`System.exit` is _the opposite_ if "exiting gracefully". You should not need it, and the reason you do probably actually does have to do with slick :) — Dima, Jul 18 '21 at 15:44

score 0 · Answer 1 · answered Jul 17 '21 at 14:42

0

This was a problem with user defined threads.

I used Await.result on the last Future and then did sys.exit(0). Also in build.sbt

I used

fork in run := true

This perfectly works

answered Jul 17 '21 at 14:42

user9920500

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Scala main class with futures not terminating

1 Answers1