Transfer-Encoding: chunked streaming input support

This adds support for handling POST/PUT request bodies sent with
chunked transfer encodings ("Transfer-Encoding: chunked").
Attention has been paid to ensure that a client cannot OOM us by
sending an extremely large chunk.

This implementation is pure Ruby as the Ragel-based
implementation in rfuzz didn't offer a streaming interface.  It
should be reasonably close to RFC-compliant but please test it
in an attempt to break it.

The more interesting part is the ability to stream data to the
hosted Rack application as it is being transferred to the
server.  This can be done regardless if the input is chunked or
not, enabling the streaming of POST/PUT bodies can allow the
hosted Rack application to process input as it receives it.  See
examples/echo.ru for an example echo server over HTTP.

Enabling streaming also allows Rack applications to support
upload progress monitoring previously supported by Mongrel
handlers.

Since Rack specifies that the input needs to be rewindable, this
input is written to a temporary file (a la tee(1)) as it is
streamed to the application the first time.  Subsequent rewinded
reads will read from the temporary file instead of the socket.

Streaming input to the application is disabled by default since
applications may not necessarily read the entire input body
before returning.  Since this is a completely new feature we've
never seen in any Ruby HTTP application server before, we're
taking the safe route by leaving it disabled by default.

Enabling this can only be done globally by changing the
Unicorn HttpRequest::DEFAULTS hash:

  Unicorn::HttpRequest::DEFAULTS["unicorn.stream_input"] = true

Similarly, a Rack application can check if streaming input
is enabled by checking the value of the "unicorn.stream_input"
key in the environment hashed passed to it.

All of this code has only been lightly tested and test coverage
is lacking at the moment.

[1] - http://tools.ietf.org/html/rfc2616#section-3.6.1

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/unicorn/const.rb b/lib/unicorn/const.rb
index 250868d..b81dce0 100644
--- a/lib/unicorn/const.rb
+++ b/lib/unicorn/const.rb
@@ -26,10 +26,12 @@ module Unicorn
     ERROR_500_RESPONSE = "HTTP/1.1 500 Internal Server Error\r\n\r\n".freeze
 
     # A frozen format for this is about 15% faster
+    HTTP_TRANSFER_ENCODING = 'HTTP_TRANSFER_ENCODING'.freeze
     CONTENT_LENGTH="CONTENT_LENGTH".freeze
     REMOTE_ADDR="REMOTE_ADDR".freeze
     HTTP_X_FORWARDED_FOR="HTTP_X_FORWARDED_FOR".freeze
     RACK_INPUT="rack.input".freeze
+    STREAM_INPUT="unicorn.stream_input".freeze
   end
 
 end