How to read each new line from file after 10 second delay with Akka?

Question

I am trying to read from file line by line with some delay.

For example:

• read and print 1st line of the file
• wait 10 seconds
• read and print 2nd line of the file
• etc

So far I have tried something like this:

final Path filePath = Paths.get('path/to/file');
final ActorSystem system = ActorSystem.create();
final Materializer materializer = ActorMaterializer.create(system);

Sink<ByteString, CompletionStage<Done>> printlnSink =
   Sink.<ByteString>foreach(chunk -> System.out.println(chunk.utf8String()));

final CompletionStage<IOResult> result = 
  FileIO.fromPath(filePath)
 .throttle(1, Duration.create(10, TimeUnit.SECONDS), 1, ThrottleMode.shaping())
 .to(printlnSink)
 .run(materializer);

But the this outbursts too many lines at a time and not one line at a time.

Any ideas how to fix it?

Answer 1

final CompletionStage<IOResult> result = 
 .via(Framing.delimiter(ByteString.fromString(System.lineSeparator()),10000,FramingTruncation.ALLOW))
  FileIO.fromPath(filePath)
 .throttle(1, Duration.create(10, TimeUnit.SECONDS), 1, ThrottleMode.shaping())
 .to(printlnSink)
 .run(materializer);

See if that works for you, framing Class documents should clarify