Check if sink.lazySink.lazyInit() doesn't do what you want.
--
Johan
Akka Team
On Tue, Oct 31, 2017 at 12:59 AM, Jason Steenstra-Pickens <
thestein...@gmail.com> wrote:
> Hi,
>
> I seem to be encountering a reoccurring problem when using Akka Streams
> and haven't found the right client API to use to solve it.
>
> The problem usually translates into:
>
> - I have some possibly infinite Source
> - I want to split it into multiple inner Sources based on some
> condition such as delimiter, count, or whatever
> - I then want to create a Sink for each inner Source dynamically and
> run each inner Flow
> - I want the backpressure, errors, completion, cancellation and stuff
> like that to be shared between the outer Flow and the inner Flow
>
> There are a few things come close but all seem to be for a slightly
> different use case, such as:
>
> - splitAt / splitWhen
> - lazy / lazyInit
> - the various hubs
>
> Here is a concrete example:
>
> 1. Reading a file in 8KB parts
> 2. Splitting the first 625 parts into a separate stream as a "chunk"
> 3. Create a HTTP source that has a URL containing the chunk number
> 4. Send the 625 parts to that source
> 5. Take the next chunk from step 2
>
> An attempt using a SubFlow looks like:
> val chunkSize = fileResponse.chunkSize
> val partsPerChunk = chunkSize / partSize
> val counts = Source {
> for {
> chunk <- 1 to Int.MaxValue
> part <- 1 to partsPerChunk
> } yield (chunk, part)
> }
> val source = FileIO.fromPath(filePath, partSize)
> .zip(counts)
> .splitAfter({ next =>
> val (_, (_, part)) = next
> part == partsPerChunk
> })
>
> This is quite nice but then there doesn't seem to be a way of getting to
> the inner Flow even if I were to create a custom Sink.
>
> It would be really awesome if SubFlow had a function like:
> def to[M](f: Out => Graph[SinkShape[Out], M]): C
> (although probably without the materialised value since there would be
> multiple).
>
> Is there something obvious that I am missing?
>
>
> Cheers,
> Jason
>
> --
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>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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