Chunked Response handling with Akka Http?

[sub...@gmail.com]

I'd like to be able to use akka-http with chunked responses. I'd like to know if I can do the same thing in akka-http as with the playframework. The following is from playframework documentation.

def index = Action {
  val source = Source.apply(List("kiki", "foo", "bar"))
  Ok.chunked(source)
}
We can inspect the HTTP response sent by the server:
HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Transfer-Encoding: chunked

4
kiki
3
foo
3
bar
0

With akka-http I was able to get close with

 val hi = Chunk("Hi" + "\n")
 val there = Chunk("there" + "\n")
 val last = LastChunk("boom" + "\n")

 val source: Source[ChunkStreamPart, NotUsed] = Source(scala.collection.immutable.Iterable(hi, there, last))

 val rootPath: Route =
   path("") {
     get {
       for (i <- 1 to 100) {
         ref ! hi
       }

       complete(Chunked(ContentTypes.`text/plain(UTF-8)`, source))
     }
   }

 def routes: Route = rootPath
}

curl returns

< HTTP/1.1 200 OK
< Server: akka
< Date: Mon, 16 Jan 2017 14:03:10 GMT
< Transfer-Encoding: chunked
< Content-Type: text/plain; charset=UTF-8
< 
Hi
there


Two perhaps minor issues: it does not report the last element, and it doesn't include the chunk size as the playframework example did.

What I’d like to know is how can I do this in a dynamic way? I'm interacting with a embedded device (via serial) where I make an async request and it responds one or more times up to about 20 seconds. I'd like each response to be emitted as a chunk. Is this possible? 

Thanks,
Andrew

[Akka Team]

This is definitely possible, just use Chunk for each element instead, that way you can create them from a stream of strings using .map()

For the "an async request and it responds one or more times" there are a few possible tools in Akka streams that may solve this. Take a look at Source.unfoldAsync, Source.unfoldResourceAsync and Source.queue and see if either of those fit your use case.

-- 

Johan

Akka Team

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