Simple test demonstrating the 5s latency of rainbows server when the HTTP response does not contain either ContentLength or Chunked Transfer-Enconding headers.
Without these headers, the server sends the response, then waits 5s, then closes the connection. Tcpdump shows no activity, then a FIN sequence with the first packet sent by the server.
The server closing the connection to indicate the end of the body is a correct behavior in the absence of the headers [1].
Rainbows includes the Rack middleware that adds these headers, but only when the RACK_ENV env var is set to 'deployment' or 'development', i.e. not 'production'.
The online documentation [2] disagrees about this with the
Documentation/rainbows.1.txt in the official git repo [3].
Apparently, this is almost a FAQ [4].
To run the test, make sure you have ruby (2.1, 2.2) and bundler gem installed. Then run in the project directory:
gem install -N bundler
bundle
./run-server slow.ru
./test
[1] http://www.w3.org/Protocols/HTTP/1.1/draft-ietf-http-v11-spec-01.html#BodyLength
Otherwise, the body length is determined by the Transfer-Encoding (if the "chunked" transfer coding has been applied), by the Content-Type (for multipart types with an explicit end-of-body delimiter), or by the server closing the connection.
[2] http://rainbows.bogomips.org/rainbows.1.html#rack-environment
[3] git://bogomips.org/rainbows.git
[4] http://bogomips.org/rainbows-public/m/20140704195032.GA13152%40dcvr.yhbt.net.html