ReactiveMongo/Play: `LastError: DatabaseException['<none>']`, while db still updates - mongodb

Question

weird problem: While my play application tries to insert/update records from some mongoDB collections while using reactivemongo, the operation seems to fail with a mysterious message, but the record does, actually, gets inserted/updated.
More info:
Insert to problematic collections from the mongo console works well
reading from all collections works well
reading and writing to other collections in the same db works well
writing to the problematic collections used to work.
Error message is:
play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[LastError: DatabaseException['<none>']]]
at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:280)
at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:206)
at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:100)
at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:99)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:70)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40)
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:248)
Caused by: reactivemongo.api.commands.LastError: DatabaseException['<none>']
Using ReactiveMongo 0.11.14, Play 2.5.4, Scala 2.11.7, MongoDB 3.4.0.
Thanks!
UPDATE - The mystery thickens!
Based on #Yaroslav_Derman's answer, I added a .recover clause, like so:
collectionRef.flatMap( c =>
c.update( BSONDocument("_id" -> publicationWithId.id.get), publicationWithId.asInstanceOf[PublicationItem], upsert=true))
.map(wr => {
Logger.warn("Write Result: " + wr )
Logger.warn("wr.inError: " + wr.inError)
Logger.warn("*************")
publicationWithId
}).recover({
case de:DatabaseException => {
Logger.warn("DatabaseException: " + de.getMessage())
Logger.warn("Cause: " + de.getCause())
Logger.warn("Code: " + de.code)
publicationWithId
}
})
The recover clause does get called. Here's the log:
[info] application - Saving pub t3
[warn] application - *************
[warn] application - Saving publication Publication(Some(BSONObjectID("5848101d7263468d01ff390d")),t3,2016-12-07,desc,auth,filename,None)
[info] application - Resolving database...
[info] application - Resolving database...
[warn] application - DatabaseException: DatabaseException['<none>']
[warn] application - Cause: null
[warn] application - Code: None
So no cause, no code, message is "'<none>'", but still an error. What gives?
I tried to move to 0.12, but that caused some compilation errors across the app, plus I'm not sure that would solve the problem. So I'd like to understand what's wrong first.
UPDATE #2:
Migrated to reactive-mongo 0.12.0. Problem persists.

Answer 1

Problem solved by downgrading to MongoDB 3.2.8. Turns out reactiveMongo 0.12.0 is not compatible with mongoDB 3.4.
Thanks everyone who looked into this.

Answer 2

For play reactivemongo 0.12.0 you can do like this
def appsDb = reactiveMongoApi.database.map(_.collection[JSONCollection](DesktopApp.COLLECTION_NAME))
def save(id: String, user: User, body: JsValue) = {
val version = (body \ "version").as[String]
val app = DesktopApp(id, version, user)
appsDb.flatMap(
_.insert(app)
.map(_ => app)
.recover(processError)
)
}
def processError[T]: PartialFunction[Throwable, T] = {
case ex: DatabaseException if ex.code.contains(10054 | 10056 | 10058 | 10107 | 13435 | 13436) =>
//Custom exception which processed in Error Handler
throw new AppException(ResponseCode.ALREADY_EXISTS, "Entity already exists")
case ex: DatabaseException if ex.code.contains(10057 | 15845 | 16550) =>
//Custom exception which processed in Error Handler
throw new AppException(ResponseCode.ENTITY_NOT_FOUND, "Entity not found")
case ex: Exception =>
//Custom exception which processed in Error Handler
throw new InternalServerErrorException(ex.getMessage)
}
Also you can add logs in processError method

Answer 3

LastError was deprecated in 0.11, replaced by WriteResult.
LastError does not, actually, means error, it could mean successful result, you need to check inError property of the LastError object to detect if it's real error. As I see, the '<none>' error message give a good chance that this is not error.
Here is the example "how it was in 0.10": http://reactivemongo.org/releases/0.10/documentation/tutorial/write-documents.html