Whatever Flow your graph(system) method call returns is the culprit here. I
don't know what that is, but we can assume it is not rate-limited in any
way. I'm guessing it is wrapping an Actor. If that's the case, I would
consider interacting with the Actor using the "akka.pattern.ask" pattern,
and
object stream2iter extends Iterator[(LogSequenceNumber, String)] {
override def next: (LogSequenceNumber, String) = {
try {
val msg = stream.read
//println(msg)
val offset = msg.arrayOffset
val src = msg.array
val len = src.length - offset
