Create a 'strictEntity' directive

[akka-ci]

Issue by Joe-Edwards
Tuesday Jul 05, 2016 at 09:45 GMT
Originally opened as akka/akka#20881

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From #20850

A Directive1[HttpEntity.Strict] which calls toStrict on the HTTP Entity safely with a specified timeout (to avoid the deadlock in the other ticket). N.B. should also replace the entity in the request context.

[akka-ci]

Comment by ktoso
Tuesday Jul 05, 2016 at 10:59 GMT

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Thanks for the ticket, I agree it's better to provide a directive whcih does this "safely" than assuming people will do the right thing (and get 20 "almost correct" impls ;-))

[akka-ci]

Comment by ktoso
Tuesday Jul 05, 2016 at 11:00 GMT

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PRs very welcome to this one, should be rather simple :)

[akka-ci]

Comment by Hawstein
Tuesday Jul 12, 2016 at 17:32 GMT

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@Joe-Edwards @ktoso I will work on this if you don't mind. And AFAICS, just adding a extractStrictRequestEntity method to BasicDirectives solves this issue. Correct me if I miss something.

[akka-ci]

Comment by Joe-Edwards
Tuesday Jul 12, 2016 at 18:36 GMT

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Go for it. If it's any help, what I'd come up with so far was:

  def extractStrictEntity(timeout: FiniteDuration): Directive1[HttpEntity.Strict] = {
    Directive { inner => ctx =>
      ctx.request.entity match {
        case strict: HttpEntity.Strict =>
          inner(Tuple1(strict))(ctx)
        case nonStrict =>
          import ctx.{executionContext, materializer}
          nonStrict.toStrict(timeout).flatMap(strict => inner(Tuple1(strict))(ctx.mapRequest(_.copy(entity = strict))))
      }
    }
  }

I'm not sure if the optimization in the strict case is really necessary (perhaps using FastFuture will make it redundant anyway?)

[akka-ci]

Comment by ktoso
Tuesday Jul 12, 2016 at 21:08 GMT

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The optimisation is not needed, toStrict does the right thing (returns "this") if the entity is Strict already.

I was more thinking of making a directive that works via mapRequest, i.e. it transforms the entity transparently.

strictEntity { // toStricts, but we can do various things inside
  extractDataBytes { // works since strict already
    // .. 
  } ~ get { 
    extractRequest { r => r.entity.dataBytes .... } 
  }
}

[akka-ci]

Comment by ktoso
Tuesday Jul 12, 2016 at 21:09 GMT

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For inspiration look at mapRequest

val route =
      mapRequest(transformToPostRequest) {
        extractRequest { req =>
          complete(s"The request method was ${req.method.name}")
        }
      }

[akka-ci]

Comment by Hawstein
Wednesday Jul 13, 2016 at 20:00 GMT

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@ktoso just make a PR for this issue.

[akka-ci]

Comment by Joe-Edwards
Thursday Jul 14, 2016 at 09:42 GMT

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The benefit of extracting the entity is that you get don't need to match/cast it. Usually you want a strict entity so you can get the data explicitly:

strictEntity(...) {
  extractRequest { request =>
    val entity: HttpEntity = request.entity // don't know it's strict yet :(
    entity match {
      case strict: HttpEntity.Strict => strict.data // now we do, but have an non-exhaustive match :(
    }
  }
}

vs

extractStrictEntity(...) { strict =>
  strict.data // immediately available in a type safe way
}

[akka-ci]

Comment by ktoso
Thursday Jul 14, 2016 at 09:59 GMT

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Sure, however it does not compose as nicely.
My proposal composes more nicely though, and is beneficial for other directives as well (e.g. formFields which people keep getting wrong), instead of just this single case.

I stand by the need of doing a directive like I proposed, and optionally adding a extractStrictEntity.

[akka-ci]

Comment by ktoso
Friday Jul 22, 2016 at 09:33 GMT

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Thanks a lot @Hawstein for implementing this feature :-)

[catalin-ursachi]

Was this not already implemented by akka/akka#20953?

[ktoso]

Correct, thanks a lot for noticing @catalin-ursachi !

[ktoso]

Duplicate of akka/akka#20881 (already solved)