HTTP client adds Content-Length header to response

[adleong]

When the HTTP client receives a 204 response with no content-length header, it appears to add a content-length header to the response object.

Expected behavior

Content-length header should not be added to the response.

Actual behavior

Content-length header is added to response.

Steps to reproduce the behavior

Consider the following snippet:

  val server = Http.serve(s":$port", Service.mk { req: Request =>
    val rsp = req.response
    rsp.contentString = ""
    rsp.statusCode = 204
    println("Response Headers Sent")
    println(rsp.headerMap)
    Future.value(rsp)
  })

  val service = Http.client.newService(Name.bound(Address(host, port)), "client")

  val req = Request()
  val rsp = Await.result(service(req))
  println("Response Headers Received")
  println(rsp.headerMap)

This prints:

INFO: Finagle version 18.9.1 (rev=63182f815cb20549ced80c99465879609b05d94b) built at 20180926-144723
Response Headers Sent
Map()
Response Headers Received
Map(content-length -> 0)

Using Wireshark, I confirmed that no content-length header is being sent over the wire.

Furthermore, if we then try to re-transmit that response, we got this log message:

Response with a status code of 204 must not have a Content-Length header field thus the field has been removed. Content-Length: 0

[bryce-anderson]

@adleong, seems like a bug. Are you interested in digging into it?

[dadjeibaah]

I dug into this a little bit more and it appears that this is a bug in Netty's HTTPObjectAggregrator here. It looks like when netty parses a full http message it sets the Content-Length header for that message even when the http message is of type 204 No Content. Based on RFC 7230 3.3.2

A server MUST NOT send a Content-Length header field in any response with a status code of 1xx (Informational) or 204 (No Content). A server MUST NOT send a Content-Length header field in any 2xx (Successful) response to a CONNECT request (Section 4.3.6 of [RFC7231]).

[bryce-anderson]

@dadjeibaah, it looks like you've run into https://github.com/netty/netty/pull/6862.