Console scala app doesn't stop when using reactive mongo driver - scala

Question

I'm playing with Mongo database through the Reactive Mongo driver
import org.slf4j.LoggerFactory
import reactivemongo.api.MongoDriver
import reactivemongo.api.collections.default.BSONCollection
import reactivemongo.bson.BSONDocument
import scala.concurrent.Future
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global
object Main {
val log = LoggerFactory.getLogger("Main")
def main(args: Array[String]): Unit = {
log.info("Start")
val conn = new MongoDriver().connection(List("localhost"))
val db = conn("test")
log.info("Done")
}
}
My build.sbt file:
lazy val root = (project in file(".")).
settings(
name := "simpleapp",
version := "1.0.0",
scalaVersion := "2.11.4",
libraryDependencies ++= Seq(
"org.reactivemongo" %% "reactivemongo" % "0.10.5.0.akka23",
"ch.qos.logback" % "logback-classic" % "1.1.2"
)
)
When I run: sbt compile run
I get this output:
$ sbt compile run
[success] Total time: 0 s, completed Apr 25, 2015 5:36:51 PM
[info] Running Main
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.
17:36:52.328 [run-main-0] INFO Main - Start
17:36:52.333 [run-main-0] INFO Main - Done
And application doesn't stop.... :/
I have to press Ctrl + C to kill it
I've read that MongoDriver() creates ActorSystem so I tried to close connection manually with conn.close() but I get this:
[info] Running Main
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.
17:42:23.252 [run-main-0] INFO Main - Start
17:42:23.258 [run-main-0] INFO Main - Done
17:42:23.403 [reactivemongo-akka.actor.default-dispatcher-2] ERROR reactivemongo.core.actors.MongoDBSystem - (State: Closing) UNHANDLED MESSAGE: ChannelConnected(-973180998)
[INFO] [04/25/2015 17:42:23.413] [reactivemongo-akka.actor.default-dispatcher-3] [akka://reactivemongo/deadLetters] Message [reactivemongo.core.actors.Closed$] from Actor[akka://reactivemongo/user/$b#-1700211063] to Actor[akka://reactivemongo/deadLetters] was not delivered. [1] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.
[INFO] [04/25/2015 17:42:23.414] [reactivemongo-akka.actor.default-dispatcher-3] [akka://reactivemongo/user/$a] Message [reactivemongo.core.actors.Close$] from Actor[akka://reactivemongo/user/$b#-1700211063] to Actor[akka://reactivemongo/user/$a#-1418324178] was not delivered. [2] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.
And app doesn't exit also
So, what am i doing wrong? I can'f find answer...
And it seems to me that official docs doesn't explain whether i should care about graceful shutdown at all.
I don't have much experience with console apps, i use play framework in my projects but i want to create sub-project that works with mongodb
I see many templates (in activator) such as: Play + Reactive Mongo, Play + Akka + Mongo but there's no Scala + Reactive Mongo that would explain how to work properly :/

Answer 1

I was having the same problem. The solution I found was invoking close on both object, the driver and the connection:
val driver = new MongoDriver
val connection = driver.connection(List("localhost"))
...
connection.close()
driver.close()
If you close only the connection, then the akka system remains alive.
Tested with ReactiveMongo 0.12

Answer 2

This looks like a known issue with Reactive Mongo, see the relevant thread on GitHub
A fix for this was introduced in this pull request #241 by reid-spencer, merged on the 3rd of February 2015
You should be able to fix it by using a newer version. If no release has been made since February, you could try checking out a version that includes this fix and building the code yourself.
As far as I can see, there's no mention of this bugfix in the release notes for version 0.10.5
Bugfixes:
BSON library: fix BSONDateTimeNumberLike typeclass
Cursor: fix exception propagation
Commands: fix ok deserialization for some cases
Commands: fix CollStatsResult
Commands: fix AddToSet in aggregation
Core: fix connection leak in some cases
GenericCollection: do not ignore WriteConcern in save()
GenericCollection: do not ignore WriteConcern in bulk inserts
GridFS: fix uploadDate deserialization field
Indexes: fix parsing for Ascending and Descending
Macros: fix type aliases
Macros: allow custom annotations
The name of the committer does not appear as well:
Here is the list of the commits included in this release (since 0.9, the top commit is the most recent one):
$ git shortlog -s -n refs/tags/v0.10.0..0.10.5.x.akka23
39 Stephane Godbillon
5 Andrey Neverov
4 lucasrpb
3 Faissal Boutaounte
2 杨博 (Yang Bo)
2 Nikolay Sokolov
1 David Liman
1 Maksim Gurtovenko
1 Age Mooij
1 Paulo "JCranky" Siqueira
1 Daniel Armak
1 Viktor Taranenko
1 Vincent Debergue
1 Andrea Lattuada
1 pavel.glushchenko
1 Jacek Laskowski
Looking at the commit history for 0.10.5.0.akka23 (the one you reference in build.sbt), it seems the fix was not merged into it.