Play + scala + reactive mongo

Play + scala + reactive mongo

• 1.
  Play + Scala+ Reactive Mongo Building a “reactive” data-access layer to mongoDB
• 2.
  About Us Max Kremer Trialfire- co-founder founded in June 2013 Autodesk - cloud solutions architect Datastay - co-founder Acquired by Autodesk 2011 Marconi Lanna Trialfire - lead developer founded in June 2013 Too many startups since 1996 to list here
• 3.
  Why “reactive” Classic SynchronousModel: With a traditional synchronous database driver, each operation blocks the current thread until a response is received. More requests = more threads waiting = poor scalability
• 4.
  What is “reactive” Fullynon-blocking and asynchronous I/O operations
• 5.
  Play and asyncI/O • Java NIO • Non-blocking, asynchronous IO • Process multiple HTTP requests with a single thread • Large number of concurrent requests can be handled with a few threads
• 6.
  Example •A Play controllerusing a Future result: package controllers import play.api.mvc.{Action, Controller} import concurrent.{ExecutionContext, Future} import ExecutionContext.Implicits.global object StuffController extends Controller { def doStuff( ) = Action { val someStuff = scala.concurrent.future { models.Stuff.fetch( ) } Async { someStuff.map(value => Ok(value)) } } }
• 7.
  A word aboutFutures •Represents a value that will be available later •Execution contexts - think “thread pools” •Futures are Monads •Layer of abstraction over multi-threading
• 8.
  Data Access Layer •ActiveRecord Design Pattern •Based on Futures •Model = Case Class + Companion Object •Stackable Traits
• 9.
  Persistence using Traits importplay.api.libs.json.Json case class User ( id : Option[BSONObjectID] , firstName: String , lastName : String , email : String , password : String) object User extends DataAccess[User] { def collectionName = “user” implicit val format = Json.format[User] }
• 10.
  The Data AccessTrait trait DataAccess[M] { def collectionName: String implicit val format: Format[M] private def db = ReactiveMongoPlugin.db private def collection = db[JSONCollection](collectionName) def insert(instance: M): (BSONObjectID, Future[LastError]) = { val id = BSONObjectID.generate (id, collection.insert(Json.toJson(instance) ++ id)) }
• 11.
  The Data AccessTrait (cont’d) def update(instance: M): Future[LastError] = { instance.id map { id => collection.update(id, Json.toJson(instance)) } getOrElse Future.successful(LastError(err = Some("Invalid ID")) } def byId(id: BSONObjectID): Future[Option[M]] = { collection.find(id).cursor.headOption map { _ flatMap { doc: JsObject => doc.asOpt[M] } } }
• 12.
  Pros •easy compared tosql •no schemas •no queries •no migration •it just works conversion from/to json automatically handled by play json api macros
• 13.
  Cons •Futures all theway down… •Futures all the way up, too... •No joins
• 14.
  Cons (cont’d) case classBook ( name : String , author: Author) case class author(name: String) { lazy val books: Seq[Book] = Book.byAuthor(this) } lazy val books: Future[Seq[Book]] = Book.byAuthor(this) val books = author.books author.books map { books => ... }
• 15.
  Links reactive mongo driver: http://reactivemongo.org/ PlayReactiveMongo plugin: https://github.com/ReactiveMongo/Play-eactiveMongo
• 16.
  The End Thanks forlistening Future[Option[Applause]] max@trialfire.com marconi@trialfire.com We’re hiring!