I'm new to Elixir and Erlang and having some issues with accessing https URLs. I've tried the Elixir-specific HTTPotion and Erlang's :inets module.
So from the iex console (Interactive Elixir):
With HTTPotion:
HTTPotion.start
HTTPotion.get("https://api.github.com")
With :inets:
:inets.start
:ssl.start
:httpc.request('https://api.github.com')
In both cases I get a giant stacktrace that essential says there is a bad match somewhere and that a state machine is terminating. I don't get this when accessing http URLs. What am I missing? Thanks.
Edit - here is the error message from HTTPotion:
iex(40)> HTTPotion.get("https://api.github.com")
** (Protocol.UndefinedError) protocol String.Chars not implemented for {:EXIT, {{{{:badmatch, ""}, [{:ssl_handshake, :dec_hello_extensions, 2, [file: 'ssl_handshake.erl', line: 1737]}, {:ssl_handshake, :decode_handshake, 3, [file: 'ssl_handshake.erl', line: 926]}, {:tls_handshake, :get_tls_handshake_aux, 3, [file: 'tls_handshake.erl', line: 155]}, {:tls_connection, :next_state, 4, [file: 'tls_connection.erl', line: 433]}, {:gen_fsm, :handle_msg, 7, [file: 'gen_fsm.erl', line: 503]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 237]}]}, {:gen_fsm, :sync_send_all_state_event, [#PID<0.227.0>, {:start, 5000}, :infinity]}}, {:gen_server, :call, [#PID<0.226.0>, {:send_req, {{:url, 'https://api.github.com', 'api.github.com', 443, :undefined, :undefined, '/', :https, :hostname}, [], :get, "", [], 5000}}, 5000]}}}
(elixir) lib/string/chars.ex:3: String.Chars.impl_for!/1
(elixir) lib/string/chars.ex:17: String.Chars.to_string/1
(httpotion) lib/httpotion.ex:157: HTTPotion.request/5
iex(40)>
16:50:10.640 [error] ** State machine #PID<0.227.0> terminating
** Last message in was {:tcp, #Port<0.7454>,
<<22, 3, 3, 0, 93, 2, 0, 0, 89, 3, 3, 84, 40, 158, 178, 2, 216, 45, 226, 183, 79, 42, 199, 205, 19, 31, 63, 223, 138, 208, 132, 186, 28, 129, 123, 235, 1, 142, 90, 243, 25, 70, 210, 32, 199, 56, 251, 131, ...>>}
** When State == :hello
** Data == [data: [{'StateData',
{:state, :client, {#Reference<0.0.0.1360>, #PID<0.226.0>}, :gen_tcp,
:tls_connection, :tcp, :tcp_closed, :tcp_error, 'api.github.com', 443,
#Port<0.7454>,
{:ssl_options, :tls, [{3, 3}, {3, 2}, {3, 1}, {3, 0}], :verify_none,
{#Function<7.50551058/3 in :ssl.handle_verify_options/2>, []},
#Function<8.50551058/1 in :ssl.handle_verify_options/2>, false, false,
:undefined, 1, "", '***', "", '***', '***', '***', "", '***', :undefined,
:undefined, '***', '***',
[<<192, 36>>, <<192, 40>>, <<192, 38>>, <<192, 42>>, <<0, 107>>,
<<0, 106>>, <<0, 61>>, <<192, 35>>, <<192, 39>>, <<192, 37>>, <<192, 41>>,
<<0, 103>>, <<0, ...>>, <<...>>, ...],
#Function<1.50551058/4 in :ssl.handle_options/1>, true, 268435456, false,
:undefined, false, :undefined, :undefined, true, :undefined, false},
{:socket_options, :binary, 0, 0, 0, false}, '***', '***', '***', 49168,
'***', 61463, :ssl_session_cache, {3, 3}, false, :undefined,
{:undefined, :undefined}, :undefined, :undefined, '***', '***', '***',
:undefined, '***', '***', '***', 53269, #Reference<0.0.0.1363>, :undefined,
'***', {false, :first}, {#PID<0.226.0>, #Reference<0.0.0.1361>},
#Reference<0.0.0.1364>, {[], []}, false, true, false, false, :undefined,
:undefined, :undefined}}]]
** Reason for termination =
** {{:badmatch, ""},
[{:ssl_handshake, :dec_hello_extensions, 2,
[file: 'ssl_handshake.erl', line: 1737]},
{:ssl_handshake, :decode_handshake, 3,
[file: 'ssl_handshake.erl', line: 926]},
{:tls_handshake, :get_tls_handshake_aux, 3,
[file: 'tls_handshake.erl', line: 155]},
{:tls_connection, :next_state, 4, [file: 'tls_connection.erl', line: 433]},
{:gen_fsm, :handle_msg, 7, [file: 'gen_fsm.erl', line: 503]},
{:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 237]}]}
16:50:10.642 [error] GenServer #PID<0.226.0> terminating
Last message: {:send_req, {{:url, 'https://api.github.com', 'api.github.com', 443, :undefined, :undefined, '/', :https, :hostname}, [], :get, "", [], 5000}}
State: {:state, 'api.github.com', 443, :undefined, #Reference<0.0.0.1352>, false, :undefined, [], true, :undefined, false, [], {[], []}, :undefined, :idle, :undefined, "", 0, 0, [], :undefined, :undefined, :undefined, :undefined, false, :undefined, :undefined, "", :undefined, false, 188446, 0, :undefined}
** (exit) exited in: :gen_fsm.sync_send_all_state_event(#PID<0.227.0>, {:start, 5000}, :infinity)
** (EXIT) an exception was raised:
** (MatchError) no match of right hand side value: ""
(ssl) ssl_handshake.erl:1737: :ssl_handshake.dec_hello_extensions/2
(ssl) ssl_handshake.erl:926: :ssl_handshake.decode_handshake/3
(ssl) tls_handshake.erl:155: :tls_handshake.get_tls_handshake_aux/3
(ssl) tls_connection.erl:433: :tls_connection.next_state/4
(stdlib) gen_fsm.erl:503: :gen_fsm.handle_msg/7
(stdlib) proc_lib.erl:237: :proc_lib.init_p_do_apply/3
nil
iex(41)>
Mystery solved. I posted this question to the Elixir-lang group and this is a known bug in Erlang OTP 17.3. The solution is to apply a patch, wait for the next version, or downgrade to OTP 17.1.
Details here: https://groups.google.com/forum/#!topic/elixir-lang-talk/xsAEzCfmRoQ
Either downgrade to Erlang 17.1 or use the latest release tag "OTP-17.3.4" from GitHub - https://github.com/erlang/otp/releases
Incase you choose to use the "OTP-17.3.4" release tag from GitHub, then once you download the source and untar/unzip it, run ./otp_build autoconf, before you run the usual build instructions (./configure, make, make install).
17.3.4 is an internal release and hence no releases are available on the official Erlang site. [source: https://twitter.com/brucify/status/537240367239016448]. Although, I do see that Erlang Solutions site has builds called 17.3 rev2.
来源：https://stackoverflow.com/questions/26090500/elixir-problems-with-https-urls