Erlang HTTP problems - http

Question

I can't make a request with Erlang/Cowboy at all. I can make one from the erlang shell but not when running a cowboy release. I've tried using the 'hackney' library as well:
hackney:start(),
{ok, _, _, Ref} = hackney:request(
get, <<"http://www.youtube.com">>, [], <<>>, [{pool, default}]
),
{ok, Body} = hackney:body(Ref),
io:format("body: ~p~n~n", [Body]),
Error:
Error in process <0.361.0> on node 'cta_erlang_backend#127.0.0.1' with exit value:
{[{reason,undef},
{mfa,{hello_handler,handle,2}},
{stacktrace,[{hackney,start,[],[]},
{hello_handler,handle,2,
[{file,"src/hello_handler.erl"},{line,18}]},
{cowboy_handler,handler_handle,4,
[{file,"src/cowboy_handler.erl"},{line,111}]},
{cowboy_protocol,execute,4,
[{file,"src/cowboy_protocol.erl"},
{line,442}]}]},
{req,[{socket,#Port<0.267>},
{transport,ranch_tcp},
{connection,keepalive},
{pid,<0.361.0>},
{method,<<"POST">>},
{version,'HTTP/1.1'},
{peer,{{10,0,0,1},40049}},
{host,<<"10.0.0.103">>},
{host_info,undefined},
{port,8080},
{path,<<"/">>},
{path_info,undefined},
{qs,<<>>},
{qs_vals,undefined},
{bindings,[]},
{headers,[{<<"host">>,<<"10.0.0.103:8080">>},
{<<"connection">>,<<"keep-alive">>},
{<<"content-length">>,<<"4">>},
{<<"cache-control">>,<<"no-cache">>},
{<<"origin">>,
<<"chrome-extension://fdmmgilgnpjigdojojpjoooidkmcomcm">>},
{<<"user-agent">>,
<<"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/39.0.2171.65 Chrome/39.0.2171.65 Safari/537.36">>},
{<<"content-type">>,<<"text/plain;charset=UTF-8">>},
{<<"accept">>,<<"*/*">>},
{<<"accept-encoding">>,<<"gzip, deflate">>},
{<<"accept-language">>,<<"en-GB,en-US;q=0.8,en;q=0.6">>}]},
{p_headers,[{<<"connection">>,[<<"keep-alive">>]}]},
{cookies,undefined},
{meta,[]},
{body_state,waiting},
{buffer,<<"asdf">>},
{multipart,undefined},
{resp_compress,false},
{resp_state,waiting},
{resp_headers,[]},
{resp_body,<<>>},
{onresponse,undefined}]},
{state,{state}}],
[{cowboy_protocol,execute,4,[{file,"src/cowboy_protocol.erl"},{line,442}]}]}
=ERROR REPORT==== 19-Oct-2016::18:56:51 ===
Ranch listener my_http_listener had connection process started with cowboy_protocol:start_link/4 at <0.361.0> exit with reason:
{[{reason,undef},{mfa,{hello_handler,handle,2}},{stacktrace,[{hackney,start,[],[]},{hello_handler,handle,2,[{file,"src/hello_handler.erl"},{line,18}]},{cowboy_handler,handler_handle,4,[{file,"src/cowboy_handler.erl"},{line,111}]},{cowboy_protocol,execute,4,[{file,"src/cowboy_protocol.erl"},{line,442}]}]},{req,[{socket,#Port<0.267>},{transport,ranch_tcp},{connection,keepalive},{pid,<0.361.0>},{method,<<"POST">>},{version,'HTTP/1.1'},{peer,{{10,0,0,1},40049}},{host,<<"10.0.0.103">>},{host_info,undefined},{port,8080},{path,<<"/">>},{path_info,undefined},{qs,<<>>},{qs_vals,undefined},{bindings,[]},{headers,[{<<"host">>,<<"10.0.0.103:8080">>},{<<"connection">>,<<"keep-alive">>},{<<"content-length">>,<<"4">>},{<<"cache-control">>,<<"no-cache">>},{<<"origin">>,<<"chrome-extension://fdmmgilgnpjigdojojpjoooidkmcomcm">>},{<<"user-agent">>,<<"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/39.0.2171.65 Chrome/39.0.2171.65 Safari/537.36">>},{<<"content-type">>,<<"text/plain;charset=UTF-8">>},{<<"accept">>,<<"*/*">>},{<<"accept-encoding">>,<<"gzip, deflate">>},{<<"accept-language">>,<<"en-GB,en-US;q=0.8,en;q=0.6">>}]},{p_headers,[{<<"connection">>,[<<"keep-alive">>]}]},{cookies,undefined},{meta,[]},{body_state,waiting},{buffer,<<"asdf">>},{multipart,undefined},{resp_compress,false},{resp_state,waiting},{resp_headers,[]},{resp_body,<<>>},{onresponse,undefined}]},{state,{state}}],[{cowboy_protocol,execute,4,[{file,"src/cowboy_protocol.erl"},{line,442}]}]}
hello_handler.erl:
-module(hello_handler).
-behaviour(cowboy_http_handler).
-export([init/3]).
-export([handle/2]).
-export([terminate/3]).
-record(state, {
}).
init(_, Req, _Opts) ->
hackney:start(),
{ok, Req, #state{}}.
handle(Req, State) ->
{Method, Req2} = cowboy_req:method(Req),
case Method of
<<"POST">> ->
{ok, _, _, Ref} = hackney:request(get, <<"http://www.youtube.com">>,
[], <<>>, [{pool, default}]),
{ok, Body} = hackney:body(Ref),
io:format("body: ~p~n~n", [Body]),
ResponseBody = <<"Hello Erl POST!">>;
<<"GET">> ->
ResponseBody = <<"Hello Erlang1!">>
end,
{ok, Req2} = cowboy_req:reply(200,
[{<<"content-type">>, <<"text/plain">>}],
ResponseBody,
Req),
{ok, Req2, State}.
terminate(_Reason, _Req, _State) ->
ok.

Answer 1

{[{reason,undef},
{mfa,{hello_handler,handle,2}},
{stacktrace,[{hackney,start,[],[]},
{hello_handler,handle,2,
[{file,"src/hello_handler.erl"},{line,18}]},
{cowboy_handler,handler_handle,4,
[{file,"src/cowboy_handler.erl"},{line,111}]},
{cowboy_protocol,execute,4,
[{file,"src/cowboy_protocol.erl"},
{line,442}]}]},
Crash at cowboy_handler.erl 111 line, https://github.com/ninenines/cowboy/blob/1.1.x/src/cowboy_handler.erl#L111
Reason: hello_handler:handle/2 is undef
So
Make sure your hello_handler.erl in src dir;
Compile it with rebar compile;
restart server or l(hello_handler) in erlang shell