Dear hakkers,
today we are very excited to share with you another early preview milestone
of Akka Streams and Akka HTTP. Version 0.6 was not widely announced because
we were preparing some major work on the API and most of that is now
finished. Behold, the new FlowGraph DSL (we have implemented Scala first,
the equivalent Java API will follow shortly):
// first define some pipeline pieces
val f1 = FlowFrom[Input].map(_.toIntermediate)
val f2 = FlowFrom[Intermediate].map(_.enrich)
val f3 = FlowFrom[Enriched].filter(_.isImportant)
val f4 = FlowFrom[Intermediate].mapFuture(_.enrichAsync)
// then add input and output placeholders
val in = SubscriberSource[Input]
val out = PublisherSink[Enriched]
(There are many more sources and sinks available, also for strict
collections, iterators, futures and promises, etc.)
/*
* then plug them together:
*
*/
val g = FlowGraph { implicit b ⇒
val bcast = Broadcast[Intermediate]
val merge = Merge[Enriched]
in ~> f1 ~> bcast ~> f2 ~> merge ~> f3 ~> out
bcast ~> f4 ~> merge
}.run()
// now get out the real ins and outs for this run
val sub = in.subscriber(g)
val pub = out.publisher(g)
The previous Flow/Duct DSL
<http://doc.akka.io/api/akka-stream-and-http-experimental/0.6/#akka.stream.package>
— which is still present in the scaladsl & javadsl packages and will be
removed in the next milestone—has now been unified in the scaladsl2 package
<http://doc.akka.io/api/akka-stream-and-http-experimental/0.6/#akka.stream.scaladsl2.package>
and sliced differently: all operations that mediate between one input
stream and one output stream (map, filter, etc.; also groupBy produces only
one primary output stream) are defined on Flow, while all other “plumbing”
operations are modeled as a graph that can capture any desired
topology—cycles are an advanced feature that needs to be explicitly enabled
though. FlowGraphs and Flows are immutable descriptions of a processing
machine that can be set in motion by the run() method, which allows you to
freely share references to these and write libraries that provide and
consume them.
The second very exciting aspect of today’s milestone release is that is
also incorporates the first part of the HTTP routing DSL that is being
ported from Spray—as a first step we just incorporate the existing Scala
part and in a second step we will add an equivalent Java API as well. To
those of you who have used Spray before it should look very familiar, on
the surface it will remain as source compatible as we can make it. Upon
closer inspection you will find that the DSL is now safer than before, its
result type is no longer Unit but RouteResult (which will result in better
compiler errors for nonsensical route definitions) and the evaluation of
all elements is now consistently “lazy”, meaning that the inner part is not
executed surprisingly for non-matching requests (that used to happen in
certain edge cases).
The third exciting item is SSL support for our Streams, you can take a look
at SslTlsFlowSpec
<https://github.com/akka/akka/blob/62a20195af79c7b405303b5f97970c9ca7a6891a/akka-stream/src/test/scala/akka/stream/io/SslTlsFlowSpec.scala>
to get an impression of how we are integrating it. Currently session
renegotiation is not yet implemented and HTTP does not know about it either.
As usual please be aware that this is still a very early development
preview, we will likely change the API over the coming weeks (we will
certainly move scaladsl2 back as scaladsl for example) but at this point
the seas are calming down and the weather should be approaching smooth
sailing conditions soon.
Happy hakking!
--
Cheers,
Konrad 'ktoso' Malawski
hAkker @ Typesafe
<http://typesafe.com>
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