Hi Mantis,
you are right, `Marshaller.withFixedContentType` is a bit restricted in
that regard. Fortunately, it is only a shortcut for simpler cases and the
full asynchronous functionality is available for marshallers. Try something
like
Marshaller[Iterator[Data], HttpResponse] { implicit ec => it =>
doSomethingWhichReturnsFutureOfHttpResponse.map { response =>
Marshalling.WithFixedContentType(contentType, () ⇒ response) :: Nil
}
}
Cheers,
Johannes
On Wednesday, September 20, 2017 at 12:10:24 PM UTC+2, Muntis Grube wrote:
>
> Hello
>
> Is there way to trick marshallers to accept my Future[HttpResponse]
> in withFixedContentType ?
>
> To provide large responses from cursor I'm trying to materialize class
> that extends Iterator. To do that we created SourceShape[ByteString] that
> wraps the iterator and
> corrseponding GraphStageWithMaterializedValue[SinkShape[ByteString],
> Future[MessageEntity]]
> that pools first values from source and decides if HttpEntity.Strict
> or HttpEntity.Chunked should be creaded.
>
>
> def httpResponse(iterator: Iterator[Data])(implicit ec: ExecutionContext
> ) = {
> Await.result(Source.fromGraph(sourceGrap(iterator)).runWith(entitySink
> ).map(entity => HttpResponse(entity = entity)), 60 seconds)
> }
>
> val toResponseIteratorJsonMarshaller: ToResponseMarshaller[Iterator[Data
> ]] =
> Marshaller.withFixedContentType(`application/json`) {
> result => httpResponse(result)
> }
>
> implicit val toResponseIteratorMarshaller: ToResponseMarshaller[Iterator
> [Data]] =
> Marshaller.oneOf(
> toResponseIteratorJsonMarshaller,
> toResponseIteratorOdsMarshaller,
> toResponseIteratorExcelMarshaller
> )
>
>
> As you can probably guess the biggest concern for me is
> unnecessary Await.result. One of the promising solutions was to drop await
> and to rewrite marshaller as:
>
> def httpResponse(iterator: Iterator[Data])(implicit ec: ExecutionContext)
> = {
> Source.fromGraph(sourceGrap(iterator)).runWith(entitySink).map(entity
> => HttpResponse(entity = entity))
> }
>
> val toResponseIteratorJsonMarshaller: ToResponseMarshaller[Iterator[Data
> ]] = Marshaller{ implicit ec => result =>
> httpResponse(result).map(response => Marshalling.WithFixedContentType(
> `application/json`, () => response ) :: Nil)
> }
>
> Unfortunately project structure is built that way that query is executed
> and cursor is opened when iterator hasNext or next methods are called. And
> in this solution it is done before content negotiation is done and causes
> multiple queries called for each response type at best or multiple queries
> on one connection at worst.
>
>
> Thanks.
> Muntis
>
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