How to process Akka stream based on some condition? - scala

Question

Suppose there is a stream of some files to be processed and only a specific file should be processed(consumed) when a condition is met.
i.e. Only if the stream contains a file named "aaa", process a file named "bbb"
SomeFile(name: String)
What would be the correct(recommended) way to do this?

Answer 1

Okay, here's an example. Be careful about building up too big a buffer here before the trigger hits
class FileFinder {
def matchFiles(triggerName: String,
matchName: String): Flow[SomeFile, SomeFile, NotUsed] =
Flow[SomeFile].statefulMapConcat(
statefulMatcher(matches(triggerName), matches(matchName)))
private def matches(matchName: String): SomeFile => Boolean = {
case SomeFile(name) if name == matchName => true
case _ => false
}
private def statefulMatcher(
triggerFilter: => SomeFile => Boolean,
sendFilter: SomeFile => Boolean): () => SomeFile => List[SomeFile] = {
var found = false
var sendFiles: List[SomeFile] = Nil
() => file: SomeFile =>
{
file match {
case f if triggerFilter(f) =>
found = true
val send = sendFiles
sendFiles = Nil
send
case f if sendFilter(f) =>
if (found)
List(f)
else {
sendFiles = f :: sendFiles
Nil
}
case _ => Nil
}
}
}
}
object FileFinder extends FileFinder {
def main(args: Array[String]): Unit = {
implicit val system: ActorSystem = ActorSystem("finder")
implicit val materializer: ActorMaterializer = ActorMaterializer()
implicit val executor: ExecutionContextExecutor =
materializer.executionContext
implicit val loggingAdapter: LoggingAdapter = system.log
val files = List(SomeFile("aaa"), SomeFile("bbb"), SomeFile("aaa"))
Source(files)
.via(matchFiles("bbb", "aaa"))
.runForeach(println(_))
.andThen({
case Success(_) =>
println("Success")
system.terminate()
case Failure(ex) =>
loggingAdapter.error("Shouldn't happen...", ex)
system.terminate()
})
}
}
case class SomeFile(name: String)