Set readPreference=secondaryPreferred in conf but still 'read' is done from primary

[Ritesh Jha]

I am having issue with reactive mongo when I tried to set readPreference in mongo db uri in application.conf. Query always executed at primary. 

mongodb.uri="mongodb://host1:27017,host2:27017,host3:27017/ecom?readPreference=secondaryPreferred"

log from my primary db:

query ecom.order query: { $readPreference: { mode: "primary" }, $query: { created_at: { $gte: new Date(1370016000000), $lte: new Date(1498838399999) }, items.store: 151 }, $hint: { created_at: 1, items.store: 1 } } planSummary: IXSCAN { created_at: 1.0, items.store: 1.0 } ntoreturn:2147483647 ntoskip:0 nscanned:32097 nscannedObjects:0 keyUpdates:0 writeConflicts:0 numYields:331 nreturned:0 reslen:20 locks:{ Global: { acquireCount: { r: 664 } }, MMAPV1Journal: { acquireCount: { r: 332 } }, Database: { acquireCount: { r: 332 } }, Collection: { acquireCount: { R: 332 } } } 105ms

But when i set readPreference in code of GenericQueryBuilder like below then it hit secondary. 

.cursor[Order](ReadPreference.secondaryPreferred) 

Am I missing any option in uri ? Please help. 

FYI

ReactiveMongo Version 0.12.4

MongoDB version 3.0.7

Operating System  MacOS 10.12.4

[Cédric Chantepie]

Hi,

Adding debug to the query builder, I can confirm that the read preference is taken in account (no regression).

scala> db.collection("foo").find(BSONDocument.empty).cursor[BSONDocument](ReadPreference.secondaryPreferred).head--> {
  $query: {

  },
  $readPreference: {
    mode: "secondaryPreferred"
  }
}
res8: scala.concurrent.Future[reactivemongo.bson.BSONDocument] = Future(<not completed>)

scala> db.collection("foo").find(BSONDocument.empty).cursor[BSONDocument](ReadPreference.secondary).head
--> {
  $query: {

  },
  $readPreference: {
    mode: "secondary"
  }
}
res9: scala.concurrent.Future[reactivemongo.bson.BSONDocument] = Future(<not completed>)

scala> db.collection("foo").find(BSONDocument.empty).cursor[BSONDocument](ReadPreference.nearest).head
--> {
  $query: {

  },
  $readPreference: {
    mode: "nearest"
  }
}
res10: scala.concurrent.Future[reactivemongo.bson.BSONDocument] = Future(<not completed>)

[Ritesh Jha]

Hi Cédric,

At query level it is working. I also mentioned that when I set readPreference in query builder it worked.

But when I set in configuration ("mongodb.uri") as per doc http://reactivemongo.org/releases/0.11/documentation/tutorial/connect-database.html query is reading from primary.

[Cédric Chantepie]

You can try 0.12.7-SNAPSHOT

[Ritesh Jha]

Hi Cédric,

I tried latest version.

"org.reactivemongo" %% "reactivemongo" % "0.12.7-SNAPSHOT",
"org.reactivemongo" %% "play2-reactivemongo" % "0.12.7-play25-SNAPSHOT"

from "Sonatype Snapshots" at "https://oss.sonatype.org/content/repositories/snapshots"

but now I am getting below exception.

java.lang.AbstractMethodError: reactivemongo.play.json.collection.JSONQueryBuilder.readPreference()Lreactivemongo/api/ReadPreference;

at reactivemongo.api.collections.GenericQueryBuilder$class.one(GenericQueryBuilder.scala:111)

at reactivemongo.play.json.collection.JSONQueryBuilder.one(collection.scala:441)

at com.redmart.mporder.dao.mongo.MPOrderMongo$$anonfun$getOrderByOrderId$1.apply(MPOrderMongo.scala:89)

at com.redmart.mporder.dao.mongo.MPOrderMongo$$anonfun$getOrderByOrderId$1.apply(MPOrderMongo.scala:89)

at scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:253)

at scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:251)

at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)

at scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.scala:121)

at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)

at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.pollAndExecAll(ForkJoinPool.java:1253)

at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1346)

at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)

at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

Please suggest what I should do to fix this. 

On Tuesday, 12 September 2017 01:12:14 UTC+8, Cédric Chantepie wrote:

You can try 0.12.7-SNAPSHOT

[Cédric Chantepie]

Make sure to clean your IVY cache.

Also note that as indicated in the documentation, "when the dependency to the Play plugin is used, no separate dependency to the ReactiveMongo driver must be declared".

[Ritesh Jha]

Thanks for suggestion. Now I am using only play plugin, clear my local cache and pointing to version "0.12.7-play25-SNAPSHOT".

But still query is hitting to primary.

query: { $readPreference: { mode: "primary" }, $query: { created_at: { $gte: new Date(1370016000000), $lte: new Date(1498838399999) }, items.merchant.sub_vendor_id: 151 } } planSummary: IXSCAN { created_at: 1.0 } ntoreturn:2147483647 ntoskip:0 nscanned:31373 nscannedObjects:31373 keyUpdates:0 writeConflicts:0 numYields:406 nreturned:0 reslen:20 locks:{ Global: { acquireCount: { r: 814 } }, MMAPV1Journal: { acquireCount: { r: 407 } }, Database: { acquireCount: { r: 407 } }, Collection: { acquireCount: { R: 407 } } } 309ms

[Cédric Chantepie]

The tests aren't reproducing such issue. Without an isolated reproducer, nothing more is actionable about that. Best regards.

[Ritesh Jha]

Hi Cédric,

Issue is with initialisation from uri mentioned in configuration. By the way in source code of GenericQueryBuilder still primaryPreferred is assigned as default value. 

[Cédric Chantepie]

That's not the case https://github.com/ReactiveMongo/ReactiveMongo/blob/master/driver/src/main/scala/api/collections/bson/bsoncollection.scala#L72 , as covered by the previously indicated test.