Is there support for compression in ReactiveMongo? - mongodb

Question

I am using ReactiveMongo as the connector for an Akka-Http, Akka-Streams project. I am creating the MongoConnection as shown below, but the data in the database is compressed using Snappy. No matter where I look, I can't find any mention of compression support in the ReactiveMongo documentation. When I try to connect to the Mongo database using a URL with the compressors=snappy flag, it returns an exception.
I looked through the source code and indeed it appears to have no mention of compression support at all. At this point I'm willing to accept a hack work around.
Can anyone help me please?
MongoConnection.fromString("mongodb://localhost:27017?compressors=snappy").flatMap(uri => driver.connect(uri))
Exception:
23:09:15.311 [default-akka.actor.default-dispatcher-6] ERROR akka.actor.ActorSystemImpl - Error during processing of request: 'The connection URI contains unsupported options: compressors'. Completing with 500 Internal Server Error response. To change default exception handling behavior, provide a custom ExceptionHandler.
java.lang.IllegalArgumentException: The connection URI contains unsupported options: compressors
at reactivemongo.api.AsyncDriver.connect(AsyncDriver.scala:227)
at reactivemongo.api.AsyncDriver.connect(AsyncDriver.scala:203)
at reactivemongo.api.AsyncDriver.connect(AsyncDriver.scala:252)
If you need a workable example, you can try this:
(You don't actually need a MongoDB container running locally for the error to be thrown)
object ReactiveMongoCompressorIssue extends App {
import scala.concurrent.Await
import scala.concurrent.duration._
implicit val actorSystem = ActorSystem("ReactiveMongoCompressorIssue")
implicit val dispatcher: ExecutionContextExecutor = actorSystem.dispatcher
final val driver = AsyncDriver()
val url = "mongodb://localhost:27017/?compressors=snappy"
val connection = Await.result(MongoConnection.fromString(url).flatMap(uri => driver.connect(uri)), 3.seconds)
assert(connection.active)
}

Answer 1

Thanks to what #cchantep said about how compression in MongoDB is handled on the server side (see the MongoDB docs here) I went back through the ReactiveMongo source code to see if there was a way to either bypass the check or remove the flag from the URL myself and connect without it.
Indeed, I found that there is a boolean flag called strictMode which determines whether ignoredOptions such as the compressors flag should cause an exception to be thrown or not. So now my connection looks like this:
MongoConnection.fromString(url).flatMap(uri => driver.connect(uri, None, strictMode = false))
The None refers to a name of a connection pool, but the other connect method I was using before doesn't use one either so this works fine.
Thank you for the help!