The Case of the Missing Data

Previously...

• I resolved a problem with erlang processes and TCP sockets.
• I identified a problem where the megaphone_socket process was not being started.
• I identified a problem where data was going into ejabberd_http but not coming out.

I put some debugging statements in ejabberd_http:receive_headers and yes, it appears that the data is making it into the system.  The code around that area is interesting for example:

receive_headers(State) ->

    SockMod = State#state.sockmod,

    Socket = State#state.socket,

    Data = SockMod:recv(Socket, 0, 300000),

    case State#state.sockmod of

    gen_tcp ->

        NewState = process_header(State, Data),

        case NewState#state.end_of_request of

            true -> ok;

            _ -> receive_headers(NewState)

        end;

    _ ->

        case Data of

        {ok, Binary} ->

            {Request, Trail} = parse_request(

                     State,

                     State#state.trail ++ binary_to_list(Binary)),

            State1 = State#state{trail = Trail},

            NewState = lists:foldl(

                 fun(D, S) ->

                    case S#state.end_of_request of

                        true -> S;

                        _ -> process_header(S, D)

                    end

                 end, State1, Request),

            case NewState#state.end_of_request of

                true -> ok;

                _ -> receive_headers(NewState)

            end;

        _ ->

            ok

        end

    end.

In particular, if the socket module is not gen_tcp, then the code assumes that the data returned is of the form 

{ok, Binary} 

If it turns out that it is not, then the following case is used:

_ -> ok

This would explain how the data was appearing to disappear when it got to ejabberd.  Taking a look at the process_header function, it expects the data to be in one of the following forms:

{ok, {http_request, Method, Uri, Version}}

{ok, {http_header, _, 'Connection'=Name, _, Conn}}

{ok, {http_header, _, 'Authorization'=Name, _, Auth}}

{ok, {http_header, _, 'Content-Length'=Name, _, SLen}}

{ok, {http_header, _, 'Accept-Language'=Name, _, Langs}}

{ok, {http_header, _, 'Host'=Name, _, Host}}

{ok, {http_header, _, Name, _, Value}}

{ok, http_eoh} when State#state.request_host == undefined

{ok, http_eoh}

{error, _Reason}

I had not known this so it looks like it's back to work for me to get megaphone_socket or some such into the correct form.

Sigh.