[erlang-questions] gen_tcp:recv problem (solved)

Matthias Lersch <>
Wed Mar 11 11:43:13 CET 2015


Hi,

I found the solution.
I had to switch to raw mode after http_eoh and do a gen_tcp:recv/3 wih 
'Content-Length'

Am 10.03.2015 um 22:33 schrieb Matthias Lersch:
> Hi,
>
> I have a problem with gen_tcp:recv...
> The Body of the first call is missing but shows up at the second call 
> causing a http_error. (full code is shown a the end of the mail)
>
> I do a gen_tcp:connect/4 with the options
> [list, {mode, list}, {reuseaddr, true}, {active, false}, {keepalive, 
> true}, {packet, http}, {send_timeout, timer:seconds(2)}]
>
> Then i send a HTTP POST request using gen_tcp:send/2 and go into a 
> "receve loop" with gen_tcp:recv/3 until i get a {error,_} (thats for 
> debugging at the moment and recv timout is set to 10 seconds)
>
> my problem is:
> - On the first call (send) i get all the headers but no content.
> - On the second call i get the content of the first call at the 
> beginning of the response causing the http_error.
>
>
> I'm sending the request to a node.js service, but the result is the 
> same if i use a dummy apache service with the same response.
> So i don't think its a problem with the Server I'm sending the request 
> to.
> The Body of the response (aka content) is always "OK"
>
> The received data from the first call looks like this (there is no 
> body with "OK", it ends with http_eoh and then a timeout after 10 
> seconds) :
>
>  {ok,{http_response,{1,1},200,"OK"}}
>  {ok,{http_header,0,"X-Powered-By",undefined,"Express"}}
>  {ok,{http_header,42,'Content-Type',undefined,"text/html; 
> charset=utf-8"}}
>  {ok,{http_header,38,'Content-Length',undefined,"2"}}
>  {ok,{http_header,3,'Date',undefined,"Tue, 10 Mar 2015 20:23:05 GMT"}}
>  {ok,{http_header,2,'Connection',undefined,"keep-alive"}}
>  {ok,http_eoh}
>     ...after 10 seconds...
>  {error,timeout}
>
> The second call then returns this (notice the OKHTTP/1.1... in the 
> first row, "OK" is the Body from the call before. It should be HTTP/1.1):
>
>  {ok,{http_error,"OKHTTP/1.1 200 OK\r\n"}}
>  {ok,{http_error,"X-Powered-By: Express\r\n"}}
>  {ok,{http_error,"Content-Type: text/html; charset=utf-8\r\n"}}
>  {ok,{http_error,"Content-Length: 2\r\n"}}
>  {ok,{http_error,"Date: Tue, 10 Mar 2015 20:23:16 GMT\r\n"}}
>  {ok,{http_error,"Connection: keep-alive\r\n"}}
>  {ok,{http_error,"\r\n"}}
>     ...after 10 seconds...
>  {error,timeout}
>
>
>
> here is the gen_server code im using for my tests.
> i run the test like this from the erl command line
> s:start_link().
> s:work(1,1). % first call without body
> s:work(1,1). % second call that fails
>
> Thanky for your help!
>
>
> %%%-------------------------------------------------------------------
> %%% @author mlersch
> %%% @copyright (C) 2015, <COMPANY>
> %%% @doc
> %%%
> %%% @end
> %%% Created : 20. Feb 2015 11:13
> %%%-------------------------------------------------------------------
> -module(s).
> -author("mlersch").
>
> %% API
> -compile(export_all).
>
> -behaviour(gen_server).
>
> %% API
> -export([
>   start_link/0,
>   send/2,
>   reconnect/4]).
>
> %% gen_server callbacks
> -export([init/1,
>   handle_call/3,
>   handle_cast/2,
>   handle_info/2,
>   terminate/2,
>   code_change/3]).
>
> -define(SERVER, ?MODULE).
>
> -record(state, {
>   connection=false,
>   host,
>   port,
>   timeout,
>   opts
> }).
>
>
> %%%===================================================================
> %%% API
> %%%===================================================================
>
> send(Processor, Data)->
>   gen_server:call(?MODULE, {send, Processor, Data}).
>
> info()->
>   gen_server:call(?MODULE,info).
>
> %%--------------------------------------------------------------------
> %% @doc
> %% Starts the server
> %%
> %% @end
> %%--------------------------------------------------------------------
> -spec(start_link() ->
>   {ok, Pid :: pid()} | ignore | {error, Reason :: term()}).
> start_link() ->
>   process_flag(trap_exit, true),
>   io:format("~p Start~n",[?MODULE]),
>   gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
>
> %%%===================================================================
> %%% gen_server callbacks
> %%%===================================================================
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% Initializes the server
> %%
> %% @spec init(Args) -> {ok, State} |
> %%                     {ok, State, Timeout} |
> %%                     ignore |
> %%                     {stop, Reason}
> %% @end
> %%--------------------------------------------------------------------
> -spec(init(Args :: term()) ->
>   {ok, State :: #state{}} | {ok, State :: #state{}, timeout() | 
> hibernate} |
>   {stop, Reason :: term()} | ignore).
> init([]) ->
>
>   State = #state{
>     host = "localhost",
>     port = 9010,
>     timeout = timer:seconds(2),
>     opts = [list, {mode, list}, {reuseaddr, true}, {active, true}, 
> {keepalive, true}, {packet, http}, {send_timeout, timer:seconds(2)}]
>   },
>
>   reconnect(State),
>   {ok, State}.
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% Handling call messages
> %%
> %% @end
> %%--------------------------------------------------------------------
> -spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
>     State :: #state{}) ->
>   {reply, Reply :: term(), NewState :: #state{}} |
>   {reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
>   {noreply, NewState :: #state{}} |
>   {noreply, NewState :: #state{}, timeout() | hibernate} |
>   {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
>   {stop, Reason :: term(), NewState :: #state{}}).
>
> handle_call({send, Processor, Data}, From, State) ->
>
>   % If we are offline, notify the caller
>   case State#state.connection of
>
>     {ok,Con}->
>
>       Request =
>         ["POST /" ++ Processor ++ " HTTP/1.1\r\n"
>           ++ "Content-Length: " ++ 
> integer_to_list(lists:flatlength(Data)) ++ "\r\n"
>           ++ "User-Agent: Erlang Client\r\n"
>           ++ "Content-Type: application/json\r\n"
>           ++ "Host: " ++ State#state.host ++ "\r\n"
>           ++ "Accept: */*\r\n"
>           ++ "\r\n", [Data]],
>
>         % Try sending the data
>         case send_and_receive(Con, Request) of
>           ok -> {reply, ok, State};
>
>           % If sending fails...
>           Error ->
>             % ...Answer the Client with a error
>             gen_server:reply(From, error),
>             io:format("~p Error: ~p~n", [?MODULE, Error]),
>
>             % ...Close the connection
>             gen_tcp:close(Con),
>             timer:sleep(500),
>
>             % ...Spawn a Process that trys to reconnect.
>             reconnect(State),
>
>             % ...Update the connection state
>             {reply, error, State#state{connection = false}}
>
>         end;
>
>       _ -> {reply, offline, State}
>   end;
>
> handle_call(info, _From, State) ->
>   {reply, State, State};
>
> handle_call(Request, _From, State) ->
>   io:format("~p CALL: ~p~n", [?MODULE, Request]),
>   {reply, ok, State}.
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% Handling cast messages
> %%
> %% @end
> %%--------------------------------------------------------------------
> -spec(handle_cast(Request :: term(), State :: #state{}) ->
>   {noreply, NewState :: #state{}} |
>   {noreply, NewState :: #state{}, timeout() | hibernate} |
>   {stop, Reason :: term(), NewState :: #state{}}).
> handle_cast({connected, Connection}, State) ->
>   io:format("~p Connected: ~p~n", [?MODULE, Connection]),
>   {noreply, State#state{connection = Connection}};
>
> handle_cast(Request, State) ->
>   io:format("~p CAST: ~p~n", [?MODULE, Request]),
>   {noreply, State}.
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% Handling all non call/cast messages
> %%
> %% @spec handle_info(Info, State) -> {noreply, State} |
> %%                                   {noreply, State, Timeout} |
> %%                                   {stop, Reason, State}
> %% @end
> %%--------------------------------------------------------------------
> -spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
>   {noreply, NewState :: #state{}} |
>   {noreply, NewState :: #state{}, timeout() | hibernate} |
>   {stop, Reason :: term(), NewState :: #state{}}).
>
> handle_info({tcp_closed, _}, State) ->
>   io:format("~p Connection closed!~n", [?MODULE]),
>   reconnect(State),
>   {noreply, State#state{connection = false}};
>
> handle_info(Info, State) ->
>   io:format("~p INFO: ~p~n", [?MODULE, Info]),
>   {noreply, State}.
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% This function is called by a gen_server when it is about to
> %% terminate. It should be the opposite of Module:init/1 and do any
> %% necessary cleaning up. When it returns, the gen_server terminates
> %% with Reason. The return value is ignored.
> %%
> %% @spec terminate(Reason, State) -> void()
> %% @end
> %%--------------------------------------------------------------------
> -spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | 
> term()),
>     State :: #state{}) -> term()).
> terminate(Reason, _State) ->
>   io:format("~p TERMINATE: ~p~n", [?MODULE, Reason]),
>   ok.
>
> %%--------------------------------------------------------------------
> %% @private
> %% @doc
> %% Convert process state when code is changed
> %%
> %% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
> %% @end
> %%--------------------------------------------------------------------
> -spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
>     Extra :: term()) ->
>   {ok, NewState :: #state{}} | {error, Reason :: term()}).
> code_change(_OldVsn, State, _Extra) ->
>   {ok, State}.
>
> %%%===================================================================
> %%% Internal functions
> %%%===================================================================
>
>
>
> %% This helper function sends the request to the server and parses the 
> response
> %% to look in it for a status 200 code. If it finds a 200 we return ok 
> otherwise error.
> %% by default we use active connections, when we are in idle to get 
> info messages about
> %% deconnections into handle_info/2
> %% but here we must change to passive mode, so we are able to parse 
> the response of this
> %% send operations. disconnect messages wont show up in passive mode 
> but will pop up when
> %% we switch bach to active mode again (even if the ocured during 
> passive mode).
> send_and_receive(Con, Request)->
>   inet:setopts(Con, [{active, false}]),
>   Response =
>   case gen_tcp:send(Con, Request) of
>     ok -> parse_response(Con);
>     E -> E
>   end,
>   inet:setopts(Con, [{active, true}]),
>   Response.
>
>
> parse_response(Con)->parse_response(Con, error).
> parse_response(Con, State)->
>   R = gen_tcp:recv(Con, 0, timer:seconds(10)),
>   io:format("PR: ~p~n",[R]),
>   case R of
>     {ok,{http_response,_,200,_}} -> parse_response(Con, ok);
>     {ok,http_eoh} ->
>       io:format("PRX: ~p~n",[gen_tcp:recv(Con, 0, timer:seconds(10))]),
>       State;
>     {error, E} -> {error, E};
>     _ -> parse_response(Con, State)
>   end.
>
> reconnect(State)->
>   spawn_link(?MODULE, reconnect, [self(), State, 
> calendar:local_time(), 1]).
>
> reconnect(Pid, State, Started, Tries)->
>   io:format("~p Connecting to host ~p on port ~p~n",[?MODULE, 
> State#state.host, State#state.port]),
>   case gen_tcp:connect(State#state.host, State#state.port, 
> State#state.opts, State#state.timeout) of
>     {ok, Connection} ->
>       io:format("~p Reconnect changing controlling process: 
> ~p~n",[?MODULE, gen_tcp:controlling_process(Connection, Pid)]),
>       gen_server:cast(?MODULE, {connected, {ok, Connection}});
>     E -> io:format("~p Reconnection failed ~p (Tried it ~p times since 
> ~p). Waiting 2sec. till retry!~n", [?MODULE, E, Tries, Started]),
>          timer:sleep(timer:seconds(2)),
>          reconnect(Pid, State, Started, Tries+1)
>   end.
>
>
>
> %%%===================================================================
> %%% Debug stuff
> %%%===================================================================
> loop(Max)->
>   lists:foreach(fun(_)->
>     timer:sleep(100),
>       spawn(fun()->
>         send("processgaac", 
> "{\"_id\":{\"$oid\":\"53B382F4BE53EE3946137430\"},\"sid\":\"07101a57ce294750bb36fa72e2ffab5d\",\"eid\":1566,\"cd\":{\"$date\":1404273396000},\"t\":\"gaac\",\"p\":{\"ua\":\"Mozilla/5.0 
> (Windows NT 6.3; WOW64; rv:30.0) Gecko/20100101 
> Firefox/30.0\",\"pt\":\"search_result\",\"rt\":\"internal\",\"gs\":[{\"g\":\"08006309\",\"p\":1650},{\"g\":\"04431464\",\"p\":1429},{\"g\":\"03932773\",\"p\":696},{\"g\":\"07563999\",\"p\":825},{\"g\":\"09100275\",\"p\":5089},{\"g\":\"06426800\",\"p\":2240},{\"g\":\"10417853\",\"p\":1180},{\"g\":\"02096458\",\"p\":1365},{\"g\":\"08798173\",\"p\":3897},{\"g\":\"03531850\",\"p\":1243},{\"g\":\"00188357\",\"p\":412},{\"g\":\"09296203\",\"p\":2495},{\"g\":\"05566143\",\"p\":1498},{\"g\":\"08006456\",\"p\":1467},{\"g\":\"04347717\",\"p\":2199},{\"g\":\"08006410\",\"p\":4499},{\"g\":\"09374110\",\"p\":3897},{\"g\":\"04187656\",\"p\":691},{\"g\":\"05010397\",\"p\":1075},{\"g\":\"07727923\",\"p\":493}],\"cats\":[\"1100068\",\"1100068\",\"1100068\",\"1100071\",\"1100043\",\"1100015\",\"1100015\",\"1100029\",\"1100355\",\"1100355\",\"1100196\",\"1100114\",\"1100013\",\"1100021\",\"1100021\",\"1100021\",\"1100021\",\"1100021\",\"1100170\",\"1571\",\"1100014\",\"1100117\",\"1100233\",\"1100107\", 
> \"1100096\",\"1100467\",\"1100094\",\"1100094\",\"1100013\",\"1100014\",\"1100014\",\"1100029\",\"1100015\",\"1100015\",\"1100017\",\"1100463\",\"1100034\",\"1100109\",\"1440\",\"1100114\",\"1100109\",\"1440\",\"1100177\",\"1100013\",\"1100191\",\"1100094\",\"1100191\",\"1100029\",\"1100029\",\"1100048\",\"1100043\",\"1100016\",\"1100210\",\"1100016\",\"1100463\",\"1226\"],\"catsc\":[\"AR02AA16\",\"79680\",\"22172\",\"30365\",\"AR01AC03\",\"24009\",\"79658\",\"66403\",\"30365\",\"22294\",\"BX01\",\"71445\",\"81085\",\"24510\",\"30365\",\"22294\",\"AD11AX01\",\"82323\",\"30365\",\"22294\",\"30365\",\"22294\",\"BB03Z\",\"81644\",\"81629\",\"25123\",\"22183\",\"22182\",\"30365\",\"30365\",\"BB01A\",\"24577\",\"66407\",\"30365\",\"AD01AE16\",\"30365\",\"AD08AC\",\"24512\",\"22206\",\"30365\",\"AN05CX\",\"81736\",\"22192\",\"30365\",\"BB03Z\",\"77677\",\"66409\",\"66407\",\"30365\",\"BX01\",\"71446\",\"79609\",\"22171\",\"30365\",\"BC01D\",\"30365\",\"BB03D\",\"82323\",\"25125\",\"22204\", 
> \"30365\",\"22294\",\"AD11AX01\",\"82997\",\"82323\",\"25125\",\"22204\",\"32455\",\"30365\",\"22294\",\"BB03Z\",\"24783\",\"81736\",\"81083\",\"81082\",\"81087\",\"39604\",\"30365\",\"AS01GX07\",\"24009\",\"22220\",\"22196\",\"79610\",\"30365\",\"22294\",\"BC01D\",\"24728\",\"30365\",\"23432\",\"30365\"],\"catsx\":[\"30365\",\"30365\",\"22294\",\"30365\",\"22294\",\"82323\",\"30365\",\"22294\",\"30365\",\"22294\",\"30365\",\"30365\",\"30365\",\"30365\",\"30365\",\"30365\",\"77677\",\"30365\",\"30365\",\"30365\",\"82323\",\"30365\",\"22294\",\"82997\",\"82323\",\"30365\",\"22294\",\"39604\",\"30365\",\"30365\",\"22294\",\"30365\",\"23432\",\"30365\"],\"fpid\":\"/aktionsartikel\",\"lt\":\"list\",\"lp\":1},\"r\":{\"s\":[{\"slid\":\"high\",\"cid\":2498,\"scr\":100000000,\"f\":1}]},\"ti\":200000000,\"to\":false,\"at\":53596,\"dv\":8,\"agg\":[],\"pad\":\"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\"}")
>       end)
>     end,
>     lists:seq(1,Max)).
>
> work(Loops, Max)->
>   lists:foreach(fun(_)-> spawn(s,loop,[Max]) end,lists:seq(1,Loops)).
>
> -- 
> ________________________________________
> Matthias Lersch, Senior Software Architect
> Tel.: +49 69 972 69 197; Fax: +49 69 972 69 204; Email: 
> 
> Kairion GmbH, Gutleutstraße 30, D-60329 Frankfurt
> Internet: http://www.kairion.de
>
>
>
>
> _______________________________________________
> erlang-questions mailing list
> 
> http://erlang.org/mailman/listinfo/erlang-questions

-- 
________________________________________
Matthias Lersch, Senior Software Architect
Tel.: +49 69 972 69 197; Fax: +49 69 972 69 204; Email: 
Kairion GmbH, Gutleutstraße 30, D-60329 Frankfurt
Internet: http://www.kairion.de

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