Debugging Futures and Iteratees in Play 2.2

Question

I'm having some strange behavior in my Play 2.2 app and I'm not sure how to go about debugging it. My code was running fine until I started using iteratees.

My actor creates an enumerator like below and sends it back to the caller:

val emailFeed = Concurrent.unicast[Message] (
          onStart = {
            pushee => {
              log.debug("Pushing 1")
              pushee.push(messages.apply(0))
              log.debug("Pushed 1")

            }
            },
          onComplete = {
            log.debug("Done with pushee")
          },
          onError = {
            (msg, in) => log.error(msg)
          }

the caller then consumes it by :

f.map { reply =>
        val emailFeed = reply.asInstanceOf[Enumerator[Message]]
        val iter =  Iteratee.fold[Message,String] ("") {
          (result, msg) =>   {
             Logger.debug("appending subj")
             result ++ msg.getSubject()
             Logger.debug(" subj appended")
             result
          }
        }
        val result: Future[String] = emailFeed |>>> iter
        Await.result(result, 10 minutes)

The problem is Await.result times out. I have stepped through the iteratee code and see it being called. There is only 1 chunk to process so it is quick. I also see the enumerator and iteratee debug stmts in the console. I just don't know why it doesn't complete:

[debug] application - Pushing 1
[debug] application - Pushed 1
[debug] application - appending subj
[debug] application -  subj appended

dres dres · Accepted Answer · 2013-10-24T18:41:26

Apparently, there isn't much feedback in Play if you forget to end your enumerator properly. You must call:

pushee.end

or

pushee.eofAndEnd

to trigger the enumerator to close and the Future to complete.

Debugging Futures and Iteratees in Play 2.2

1 Answers