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Cassandra: check isFullyFetched before completion #1935

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Oct 15, 2019
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Cassandra: check isFullyFetched before completion #1935

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21 changes: 15 additions & 6 deletions cassandra/src/main/scala/akka/stream/alpakka/cassandra/impl/CassandraSourceStage.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -36,18 +36,22 @@ import scala.util.{Failure, Success, Try}
}(exec)
}

private[this] def fetch(rs: ResultSet): Unit = {
isFetching = true
// fetch next page
val gFut = rs.fetchMoreResults()
val exec = materializer.executionContext
GuavaFutures.invokeTryCallback(gFut, exec)(futFetchedCallback)
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should this be using an async call back?

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It looks OK to me, it is only called within synchronous code.
tryPushAfterFetch is called via the async handler futFetchedCallback when the future returns.

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Yes, I just refactored it out into a method to not duplicate code.

}

setHandler(
out,
new OutHandler {
override def onPull(): Unit = maybeRs.foreach { rs =>
val currentlyAvailableRows = rs.getAvailableWithoutFetching

if (!isFetching && currentlyAvailableRows < minimumPreFetchSize) {
isFetching = true
// fetch next page
val gFut = rs.fetchMoreResults()
val exec = materializer.executionContext
GuavaFutures.invokeTryCallback(gFut, exec)(futFetchedCallback)
fetch(rs)
}

if (currentlyAvailableRows > 0)
Expand All @@ -69,8 +73,13 @@ import scala.util.{Failure, Success, Try}
if (isAvailable(out)) {
push(out, rs.one())
}
} else {
} else if (rs.isFullyFetched) {
// Only once the rs has no results left can we complete.
completeStage()
} else {
// It can happen that `getAvailableWithoutFetching` is 0, but the result set has more
// rows available. E.g. when fetchSize is relativley small and downstream consumer is fast.
fetch(rs)
}

case Failure(failure) => failStage(failure)
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