From the RFC:
The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metainformation contained
in the HTTP headers in response to a HEAD request SHOULD be identical
to the information sent in response to a GET request.
Replaces the 'Connection' interpretation in cowboy_http_protocol
from raw value to the parsed value, looking for a single token
matching close/keep-alive instead of the whole raw value (which
could contain more than one token, for example with Firefox 6+
using websocket).
Introduce the functions cowboy_http_req:parse_header/2 and /3
to semantically parse the header values and return a proper
Erlang term.
It removes all the non-essential data from the HTTP request record.
It allows some applications to make better use of their memory,
for example websockets which do not need to keep all the headers
information and can simply discard it using this function.
The formatted date is generated and kept up to date regularly
by a gen_server process storing it in the cowboy_clock ets table.
Then it is retrieved by other processes simply by reading the table.
The dispatcher now accepts '...' as the leading segment of Host and the
trailing segment of Path, this special atom matches any remaining path tail.
When given "cowboy.bugs.dev-extend.eu", host rule ['...', <<"dev-extend">>,
<<"eu">>] matches and fills host_info with [<<"cowboy">>, <<"bugs">>].
When given "/a/b/c/d", path rule [<<"a">>, <<"b">>, '...'] matches and fills
path_info with [<<"c">>, <<"d">>].
The server now does a single recv (or more, but only if needed)
which is then sent to erlang:decode_packet/3 multiple times. Since
most requests are smaller than the default MTU on many platforms,
we benefit from this greatly.
In the case of requests with a body, the server usually read at
least part of the body on the first recv. This is bufferized
properly and used when later retrieving the body.
In the case of pipelined requests, we can end up reading many
requests in a single recv, which are then handled properly using
only the buffer containing the received data.
The type isn't exported by OTP so we don't win much.
Also, inet.erl and file.erl define posix() différently,
so OTP needs to stop being so confuse in the first place
before we can attempt to use it properly.
Now the server defines default headers that can be overwritten by the
handler simply by passing them to the reply/4 function. Default headers
include, for now, Connection and Content-Length headers. Note that it isn't
enough to change the Connection header to close a keep-alive connection
server-side.
Of course since requests are a record the response state can be explicitly
overriden, but standard use prevents errors by making sure only one reply
is sent.
