HTTP over TChannel

This document outlines how we encode HTTP over TChannel.

For HTTP call requests the as (arg scheme) transport header must be set to http. Requests will be made with call req messages and responses will be sent using call res messages, with values for arg1, arg2 and arg3 as defined below.

The HTTP arg scheme does not support dispatch on arg1, all dispatching decisions must be made on the service field.


  • arg1 is an arbitrary circuit string, which can be left empty
  • arg2 is encoded request/response meta data detailed below
  • arg3 is a raw byte stream piped through from the http request/response

arg2: request meta data

Binary schema:

numHeaders:2 (headerName~2 headerValue~2){numHeaders}

Notes: - the url field's length is encoded as a varint

arg2: response meta data

Binary schema:

numHeaders:2 (headerName~2 headerValue~2){numHeaders}

Notes: - statusCode is the HTTP status code - message is utf-8 encoded - the message field's length is encoded as a varint - the headers section is to be implemented as a multi-map, or list of pairs; a single-valued map is insufficient