Creating a time-based chunking Enumeratee

Question

I want to create a Play 2 Enumeratee that takes in values and outputs them, chunked together, every x seconds/milliseconds. That way, in a multi-user websocket environment with lots of user input, one could limit the number of received frames per second.

I know that it's possible to group a set number of items together like this:

val chunker = Enumeratee.grouped(
  Traversable.take[Array[Double]](5000) &>> Iteratee.consume()
)

Is there a built-in way to do this based on time rather than based on the number of items?

I was thinking about doing this somehow with a scheduled Akka job, but on first sight this seems inefficient, and I'm not sure if concurency issues would arise.

Answer 1

How about like this? I hope this is helpful for you.

 package controllers

 import play.api._
 import play.api.Play.current
 import play.api.mvc._
 import play.api.libs.iteratee._
 import play.api.libs.concurrent.Akka
 import play.api.libs.concurrent.Promise

 object Application extends Controller {

   def index = Action {
     val queue = new scala.collection.mutable.Queue[String]
     Akka.future {
       while( true ){
         Logger.info("hogehogehoge")
         queue += System.currentTimeMillis.toString
         Thread.sleep(100)
       }
     }
     val timeStream = Enumerator.fromCallback { () =>
       Promise.timeout(Some(queue), 200)
     }
     Ok.stream(timeStream.through(Enumeratee.map[scala.collection.mutable.Queue[String]]({ queue =>
       var str = ""
       while(queue.nonEmpty){
         str += queue.dequeue + ", "
       }
       str
     })))
   }

 }

And this document is also helpful for you. http://www.playframework.com/documentation/2.0/Enumerators

UPDATE This is for play2.1 version.

 package controllers

 import play.api._
 import play.api.Play.current
 import play.api.mvc._
 import play.api.libs.iteratee._
 import play.api.libs.concurrent.Akka
 import play.api.libs.concurrent.Promise
 import scala.concurrent._
 import ExecutionContext.Implicits.global

 object Application extends Controller {

   def index = Action {
     val queue = new scala.collection.mutable.Queue[String]
     Akka.future {
       while( true ){
         Logger.info("hogehogehoge")
         queue += System.currentTimeMillis.toString
         Thread.sleep(100)
       }
     }
     val timeStream = Enumerator.repeatM{
       Promise.timeout(queue, 200)
     }
     Ok.stream(timeStream.through(Enumeratee.map[scala.collection.mutable.Queue[String]]({ queue =>
       var str = ""
       while(queue.nonEmpty){
         str += queue.dequeue + ", "
       }
       str
     })))
   }

 }