Hi there,
Just to chip in for balance.
We're using akka http and the DSL in a real world business app.
The fact we don't have hundreds of routes or don't have to call 10s of
actors per request doesn't make our app any less a "real world business
app".
Just that ours is small. And we're creating more apps this way and they
too will be fairly small (call them microservices if you must) and we're
happy to use the DSL.
Choice of solution is always context-dependent, so in the context of a
big and complicated service perhaps the low-level api can be a better fit.
Not a reason to call the DSL an anti-pattern though, IMO.
Cheers,
Michal
On 19/04/17 04:57, Konrad Malawski wrote:
For starters: It's fine if your preference is to not use the DSL, no
one will force you to; and that's also the reason the DSL is a
separate artifact.
Also, your route here is definitely multiple things and those should
be split up.
Why make one huge route, make many vals with the small pieces (e.g.
all the path prefixed parts in a real app would be in different traits
in single vars) and then simply combine them.
If your specific complaint is about the missing ~, that's solved in
two ways:
*1) just don't use ~. Use concat :-)*
concat(
get {
complete("ok")
},
path("hello") {
complete("ok")
}
)
2) JetBrains is actively working on adding Akka support, all across
the board, including routes and other things in plain actors etc.
One of the issues I opened and is being worked on right now is the ~
problem: https://youtrack.jetbrains.com/issue/SCL-11632
<https://youtrack.jetbrains.com/issue/SCL-11632#tab=History>
--
Konrad `ktoso` Malawski
Akka <http://akka.io> @ Lightbend <http://lightbend.com>
On 19 April 2017 at 12:48:21, kraythe (kray...@gmail.com
<mailto:kray...@gmail.com>) wrote:
Sorry, I have been buried with work.
The problem with the DSL approach in my opinion is that it leaves too
much space for error and strange things happening and at the same
time it hamstrings you into a particular flow that may or may not be
appropriate to the problem. Just to have some fun, this route doesn't
work. It compiles just fine, the server comes up but nothing happens.
Spot the problem?
|valroute ={path("orders"){authenticateBasic(realm ="admin
area",myAuthenticator){user =>get
{encodeResponseWith(Deflate){complete {// marshal custom object with
in-scope marshallerretrieveOrdersFromDB }}}~post {// decompress
gzipped or deflated requests if requireddecodeRequest {// unmarshal
with in-scope unmarshallerentity(as[Order]){order =>complete {// ...
write order to DB"Order received"}}}}}}~// extract URI path element
as IntpathPrefix("order"/IntNumber){orderId =>pathEnd {(put
|parameter('method!"put")){// form extraction from multipart or
www-url-encoded
formsformFields(('email,'total.as[Money])).as(Order){order =>complete
{// complete with serialized Future result(myDbActor
?Update(order)).mapTo[TransactionResult]}}}~get {// debugging
helperlogRequest("GET-ORDER"){// use in-scope marshaller to create
completer functioncompleteWith(instanceOf[Order]){completer =>//
customprocessOrderRequest(orderId,completer)}}}}path("items"){get {//
parameters to case class
extractionparameters(('size.as[Int],'color?,'dangerous?"no")).as(OrderItem){orderItem
=>// ... route using case class instance created from// required and
optional query parameterscomplete("")//
hide}}}}~pathPrefix("documentation"){// optionally compresses the
response with Gzip or Deflate// if the client accepts compressed
responsesencodeResponse {// serve up static content from a JAR
resourcegetFromResourceDirectory("docs")}}~path("oldApi"/Remaining){pathRest
=>redirect("http://oldapi.example.com/"+pathRest,MovedPermanently)}}|
If you got that there is one missing ~ between the routes you have a
sharp eye but the DSL wont tell you, the code compiles just fine. But
there I thought the DSL was supposed to make everything easy. Nope,
if you put directives in the wrong order, nest them in the wrong
order, or anything like that the code doesnt warn you, it just
refuses to run. Yes, you can scream "unit test everything" but
really? Is this untyped Ruby here? Testing everything is not a
strategy that scales well in business or endures in a long running
codebase, its an academic construct that eventually crumbles under
the real world.
The other problem with the routing is that it ties you into a certain
set of directives and techs and breaking out of that is painful. Lets
say you like the validation checking of Play-json over Spray-json?
Can it be integrated with the route? With difficulty maybe but then
you dont get the ability to handle errors like you do with the low
level API. If the body doesnt parse out to the type the route blows
up and the user gets back an internal error. What if I dont want to
tell my users how to hack json to feed to my site? What if I dont
want actors blowing up on internal errors? If so then I am up a creek
of thin ice.
Subsequent to my OP, I sat down and worked with the DSL for a good
week, integrating it into the business project I am working on. It
was painful. Missing tilde causes routes to not work, wrong nesting,
wrong order of directives, not able to validate my json and return
better error structures or handle things conditionally. It turned
into a royal nightmare and it was entirely unnecessary. I switched
back to using the low level api and other than some annoyances with
handling headers that could be nicer, it just worked. I have
flexibility to return what I want, when I want. I can offload to an
actor that calls 10 other actors and integrates the results of the
other actors into one actor and so on. In short, yes it was a bit
more verbose but it was clear, easier to understand, easier to
maintain, static type checked and solid.
My personal conclusion is that the DSL is fine for simple projects
but once you get into a real world business app, it starts to get in
the way and frustrate.
-- Robert
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