Hi,
What is the correct way to create a source from a function which returns
Future[Option[A]], besides a custom GraphStage?
The source should emit A elements (not wrapped in Future[Option[]]).
I considered a few options, none of them worked
*First: using RestartSource*
RestartSource.withBackoff(1.second, 1.second, 0.2) { () =>
Source(Stream.continually(getNextItem.map(_.getOrElse(throw new
NoSuchElementException)))).mapAsync(4)(identity)
}
This method drops elements
*Second: filtering*
Source(Stream.continually(getNextItem)).mapAsync(4)(identity).collect {
case Some(e) => a
}
This method will create too many unnecessary calls to the resource (imagine
a database) and cause DOS.
So what is the idiomatic / preferable way?
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