Lookup custom header in response headers

[Kyrylo Stokoz]

Hi All,

I`m trying to extract custom header from response object like this:

response.header[`X-Transaction-Id`]

but it always give me None, changing it to lookup by name return expected value.

response.headers.find(_.lowercaseName() == `X-Transaction-Id`.name.toLowerCase)

It looks like it is related to modeling custom headers as RawHeader.
According to http://doc.akka.io/docs/akka-http/10.0.5/scala/http/common/http-model.html:
"Thanks to extending ModeledCustomHeader instead of the plain CustomHeader such header can be matched"

Should it apply to header extraction in the way above as well? Is it a bug? or as designed?

Regards,
Kyrylo 

[Konrad Malawski]

Hi Kyrylo,

Would you mind sharing your code for the transaction id header?

That way of extracting a header does work, and I've added a test as we were missing that specific style actually:

https://github.com/akka/akka-http/pull/1047 

I suspect you may have done something wrong in your header definition - are you sure you defined everything that's needed?

See this test for more usage examples: https://github.com/akka/akka-http/blob/master/akka-http-tests/src/test/scala/akka/http/scaladsl/server/ModeledCustomHeaderSpec.scala 

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Cheers,

Konrad 'ktoso' Malawski

Akka @ Typesafe

[Marco Yuen]

Hi Konrad,

I'm don't mean to hijack the thread, but I'm having the same question.

Here is the custom header:

final case class RateLimitLimit(limit: String) extends ModeledCustomHeader[RateLimitLimit] {
  override def companion: ModeledCustomHeaderCompanion[RateLimitLimit] = RateLimitLimit

  override def renderInRequests(): Boolean = true

  override def renderInResponses(): Boolean = true

  override def value(): String = limit
}

object RateLimitLimit extends ModeledCustomHeaderCompanion[RateLimitLimit] {
  override def name: String = "X-RateLimit-Limit"

  override def parse(value: String): Try[RateLimitLimit] = Success(RateLimitLimit(value))
}

When I tried to extract the header from HttpResponse using resp.header[RateLimitLimit], I always get None. However, if I use resp.header[RawHeader], I will get my custom header back, but only if there only one custom header in the response. If the response contains more than one custom headers, resp.header[RawHeader] will return first custom header.

I'm using akka-http 10.0.6 and akka 2.5.1.

Best,
Marco

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[Greg Methvin]

It works in Konrad's unit test because that actually inserts an instance of the custom header class into the headers, as opposed to having Akka HTTP parse the response headers from an actual HTTP response. I don't think the header parsing code is able to parse to the custom header types.

Greg

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Greg Methvin

Tech Lead - Play Framework

Lightbend, Inc.

[Konrad Malawski]

To clarify: You'll notice that it does actually work in the routing DSL, even if you supply a RawHeader it will attempt to extract the typed modeled header that you provide it with. 

This actually does work in the routing DSL:

      val routes = headerValueByType[ApiTokenHeader]() { token ⇒

        complete(s"extracted> $token")

      }

      Get().withHeaders(RawHeader("apiKey", "TheKey")) ~> routes ~> check {

        status should ===(StatusCodes.OK)

        responseAs[String] should ===("extracted> apiKey: TheKey") // so it matched the custom one

      }

https://github.com/akka/akka-http/blob/master/akka-http-tests/src/test/scala/akka/http/scaladsl/server/ModeledCustomHeaderSpec.scala#L113:L120

Seems we omitted to add the special logic that can do this to the HttpRequest / HttpResponse itself, since they are "low level", 

and usually did not do these things... I'll take a look if we could add that infrastructure there without breaking binary compatibility.

-- 
Konrad `ktoso` Malawski
Akka @ Lightbend

[Greg Methvin]

Okay, that makes sense. Thanks Konrad.

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[Konrad Malawski]

I made it work in Scala: https://github.com/akka/akka-http/pull/1103

It's a bit sneaky internally, but I'd be ok with such impl.

Sadly it does not translate directly to JavaDSL and that we'll have to deal with in a different style.

Cheers,

Konrad 'ktoso' Malawski

Akka @ Lightbend