Topic (Pub\Sub)

ITopic is a very simple interface for Pub/Sub multicast pattern.

Topic

To listen to a topic, register a callback function by calling onMessage:

val topic = hz.getTopic[String]("topic")
val registration = topic.onMessage() { message =>
  println(s"Received: $message")
}
registration.cancel()

The onMessage method returns a ListenerRegistration object, which has a single method, cancel().

Reliable topic

A reliable topic uses a RingBuffer internally to ensure more reliable operation, and allows subscribers to ask for previously published messages, so long as they are not expired.

val rTopic = hz.getReliableTopic[String]("reliableTopic")

// Subscribe with replay from sequence 5:
val registration = rTopic.onSeqMessage(startFrom = 5) {
  case (seq, message) => println(s"Received $seq: $message")
}

// Or simply subscribe to new only, with sequence number:
val registration = rTopic.onSeqMessage() {
  case (seq, message) => println(s"Received $seq: $message")
}

// Or without sequence number, like regular topic:
val registration = rTopic.onMessage() { message =>
  println(s"Received: $message")
}

Any exception thrown inside the callback function is considered terminal and will cancel the registration. Employ a try/catch pattern to exempt as needed.