[erlang-questions] gen_tcp very slow to fetch data

ERLANG <>
Mon Nov 16 18:59:39 CET 2009


Hi Chandru !

That's fix my problem. Thanks.
While googling a bit, I found two ways to read from the Socket:

recv(Socket, Bin) ->
     receive
         {tcp, Socket, B} ->
             io:format(".", []),
             recv(Socket, concat_binary([Bin, B]));
         {tcp_closed, Socket} ->
             {ok, Bin};
         Other ->
             {error, {socket, Other}}
	after
	    ?TIMEOUT ->
             {error, {socket, timeout}}
     end.

% version 2 with "gen_tcp:recv"
recv2(Socket, Bin) ->
     case gen_tcp:recv(Socket, 0, ?TIMEOUT) of
          {ok, B} ->
              io:format(".", []),
              recv(Socket, concat_binary([Bin, B]));
          {error, closed} ->
              {ok, Bin};
         {error, timeout} ->
              {error, {socket, timeout}};
          Other ->
              {error, {socket, Other}}
      end.


Which one is the best in my case (see below: fetch.erl)?

Regards
Zabrane

Le 16 nov. 09 à 18:53, Chandru a écrit :

> You are expecting the server to indicate end of response by closing  
> the
> connection, but because you specify HTTP/1.1 in the request, the  
> server is
> holding up your connection, and you are timing out. Try replacing  
> HTTP/1.1
> with HTTP/1.0 in your request, or parse the response to detect end of
> response.
>
> cheers
> Chandru
>
> 2009/11/16 zabrane Mikael <>
>
>> Hi List !
>>
>> New to Erlang, I'm trying to implement a simple URL fetcher.
>> Here's my code (please, feel free to correct it if you find any bug  
>> or know
>> a better approach):
>>
>>
>> 8 
>> -----8 
>> -----8 
>> -----8-----8-----8-----8-----8-----8-----8-----8-----8-----8----
>> -module(fetch).
>>
>> -export([url/1]).
>>
>> -define(TIMEOUT,    7000).
>> -define(TCP_OPTS,   [binary, {packet, raw}, {nodelay, true},
>>                    {active, true}]).
>>
>> url(Url) ->
>>   {ok, _Tag, Host, Port} = split_url(Url),
>>
>>   Hdrs = [],
>>   Request = ["GET ", Url, " HTTP/1.1\r\n", Hdrs, "\r\n\r\n"],
>>
>>   case catch gen_tcp:connect(Host, Port, ?TCP_OPTS) of
>>     {'EXIT', Why} ->
>>           {error, {socket_exit, Why}};
>>       {error, Why} ->
>>           {error, {socket_error, Why}};
>>       {ok, Socket} ->
>>           gen_tcp:send(Socket, list_to_binary(Request)),
>>           recv(Socket, list_to_binary([]))
>>   end.
>>
>> recv(Socket, Bin) ->
>>   receive
>>       {tcp, Socket, B} ->
>>           io:format(".", []),
>>           recv(Socket, concat_binary([Bin, B]));
>>       {tcp_closed, Socket} ->
>>           {ok, Bin};
>>       Other ->
>>           {error, {socket, Other}}
>> after
>>   ?TIMEOUT ->
>>           {error, {socket, timeout}}
>>   end.
>>
>>
>> split_url([$h,$t,$t,$p,$:,$/,$/|T]) ->  split_url(http, T);
>> split_url(_X)                       ->  {error, split_url}.
>>
>> split_url(Tag, X) ->
>>   case string:chr(X, $:) of
>>       0 ->
>>           Port = 80,
>>           case string:chr(X,$/) of
>>               0 ->
>>                   {ok, Tag, X, Port};
>>               N ->
>>                   Site = string:substr(X,1,N-1),
>>                   {ok, Tag, Site, Port}
>>           end;
>>       N1 ->
>>           case string:chr(X,$/) of
>>               0 ->
>>                   error;
>>               N2 ->
>>                   PortStr = string:substr(X,N1+1, N2-N1-1),
>>                   case catch list_to_integer(PortStr) of
>>                       {'EXIT', _} ->
>>                           {error, port_number};
>>                       Port ->
>>                           Site = string:substr(X,1,N1-1),
>>                           {ok, Tag, Site, Port}
>>                   end
>>           end
>>   end.
>>
>>
>> 8 
>> -----8 
>> -----8 
>> -----8-----8-----8-----8-----8-----8-----8-----8-----8-----8------
>>
>> When testing it, the receiving socket gets very very slow:
>> $ erl
>> 1> c(fetch).
>> 2> Bin = fetch:url("http://www.google.com").
>> ......{error,{socket,timeout}}
>>
>> Am I missing something?
>> What I like to get at the end is a very fast fetcher. Any hint?
>>
>> Regards
>> Zabrane
>>



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