Scala Playframework not all DB queries get executed

问题

I'm sending via HTTP Post Request a Json to my Playframework backend.

In my backend I validate the Json to a Model. After that, I want to save the entries in my Model to my DB.

   def parseJSON: Action[AnyContent] = Action.async {
       request =>
         Future {
           request.body.asJson.map(_.validate[MyModel] match {
             case JsSuccess(items, _) =>
               itemsToDBController.saveItems(items)
               Ok("Success")
             case JsError(err) =>
               println(err)
               BadRequest("Json Parse Error")
           }).getOrElse(BadRequest("Error"))
         }
     }

One Item consists out of several objects. To save all objects to my DB, I need to get some values. Therefore I'm using a for(..) yield(...):

   def saveItems(items: MyModel) = {
       items.SomeObject.map(obj => {
         if (obj.value1.isDefined &&
           obj.value2.isDefined ) {
           val result = for (
             value1Exists <- value1DTO.checkExists(obj.value1.name);
             value1Entry <- getOrCreateValue1(value1Exists, obj);
             value2Exists <- value2DTO.checkExists(obj.value2.name);
             value2Entry <- getOrCreateValue2(value1Exists, obj)
            ) yield(value1Entry, value2Entry)

           result.map({
             case (value1Entry, value2Entry) => {
               insertAllValue3(value1Entry, value2Entry)
               Future.successful()
             }
             case _ => Future.failed(new Exception("Not all entries defined"))
           })
         }
         else {
             Future.successful("Not all objects defined - skipping")
         }
       })
     }

My problem is, after all result.map({...}) have started, my parseJSON Action returns 200 - OK. But not all relevant items get stored to my DB. It seems like after the 200 - OK everything is stopped and it doesn't even throw an error. I don't want to use Await.result or anything blocking in my Action.

Thanks in Advance

回答1:

You are starting computations by calling itemsToDBController.saveItems(items) and then immediately return result with Ok("Success"). So exception may be thrown after request if completed.

To fix this issue you need to transform result of itemsToDBController.saveItems from List[Future[T]] to Future[List[T]] with help of Future.sequence. Then call map method on returned future. Call recover on this Future to find which error is thrown:

def parseJSON: Action[AnyContent] = Action.async { request =>
  request.body.asJson
    .map(_.validate[MyModel] match {
      case JsSuccess(items, _) =>
        Future
          .sequence(itemsToDBController.saveItems(items))
          .map(_ => Ok("Success"))
          .recover {
            case e: Exception => BadRequest(e.getMessage())
          }

      case JsError(err) =>
        println(err)
        Future.successful(BadRequest("Json Parse Error"))
    })
    .getOrElse(Future.successful(BadRequest("Error")))
}

Update

For running all inserts in one transaction you should combine DBIOAction instead of Future. For example you rewrite checkExists(name) as:

def checkExists(name: String): DBIO[Boolean] = {
  Objects.filter(obj => obj.name === name).exists
}

getOrCreateValue(exists, obj) as:

def getOrCreateValue(exists: boolean, obj: Object): DBIO[Object] = {
  if (exists) {
    Objects.filter(o => o.name === name).result.head
  } else {
    (Objects returning Objects.map(_.id) into ((o, id) => o.copy(id = Some(id)))) += obj
  }
}

Now you can run it in single transaction in the following way:

def saveItems(items: MyModel) = {
  val insertActions = items.SomeObject.map(obj => {
    if (obj.value1.isDefined && obj.value2.isDefined) {
      val result = for {
        value1Exists <- value1DTO.checkExists(obj.value1.name);
        value1Entry <- getOrCreateValue1(value1Exists, obj);
        value2Exists <- value2DTO.checkExists(obj.value2.name);
        value2Entry <- getOrCreateValue2(value1Exists, obj)
      } yield (value1Entry, value2Entry)

      result.flatMap({
        case (value1Entry, value2Entry) => {
          insertAllValue3(value1Entry, value2Entry) // This also returns instance of `DBIOAction`
        }
        case _ =>
          DBIO.failed(new Exception("Not all entries defined"))
      })
    } else {
      DBIO.successful("Not all objects defined - skipping")
    }
  })
  db.run(DBIO.sequence(inserActions).transactionally)
}

For mo info how to work with DBIO actions check this official docs

来源：https://stackoverflow.com/questions/53522195/scala-playframework-not-all-db-queries-get-executed