ranch 源码分析（二）

接上ranch 源码分析（一）

上次讲到了ranch.erl的start_listener函数，下面我们详细分析下这个函数

-module(ranch).
%...... 省略若干行
-spec start_listener(ref(), non_neg_integer(), module(), any(), module(), any())
    -> supervisor:startchild_ret().
start_listener(Ref, NbAcceptors, Transport, TransOpts, Protocol, ProtoOpts)
        when is_integer(NbAcceptors) andalso is_atom(Transport)
        andalso is_atom(Protocol) ->
    _ = code:ensure_loaded(Transport),
    %% @todo Remove in Ranch 2.0 and simply require ssl.
    _ = ensure_ssl(Transport),
    case erlang:function_exported(Transport, name, 0) of
        false ->
            {error, badarg};
        true ->
            Res = supervisor:start_child(ranch_sup, child_spec(Ref, NbAcceptors,
                    Transport, TransOpts, Protocol, ProtoOpts)),
            Socket = proplists:get_value(socket, TransOpts),
            case Res of
                {ok, Pid} when Socket =/= undefined ->
                    %% Give ownership of the socket to ranch_acceptors_sup
                    %% to make sure the socket stays open as long as the
                    %% listener is alive. If the socket closes however there
                    %% will be no way to recover because we don‘t know how
                    %% to open it again.
                    Children = supervisor:which_children(Pid),
                    {_, AcceptorsSup, _, _}
                        = lists:keyfind(ranch_acceptors_sup, 1, Children),
                    %%% Note: the catch is here because SSL crashes when you change
                    %%% the controlling process of a listen socket because of a bug.
                    %%% The bug will be fixed in R16.
                    catch Transport:controlling_process(Socket, AcceptorsSup);
                _ ->
                    ok
            end,
            Res
    end.

%...... 省略若干行
-spec child_spec(ref(), non_neg_integer(), module(), any(), module(), any())
    -> supervisor:child_spec().
child_spec(Ref, NbAcceptors, Transport, TransOpts, Protocol, ProtoOpts)
        when is_integer(NbAcceptors) andalso is_atom(Transport)
        andalso is_atom(Protocol) ->
    %% @todo Remove in Ranch 2.0 and simply require ssl.
    _ = ensure_ssl(Transport),
    {{ranch_listener_sup, Ref}, {ranch_listener_sup, start_link, [
        Ref, NbAcceptors, Transport, TransOpts, Protocol, ProtoOpts
    ]}, permanent, infinity, supervisor, [ranch_listener_sup]}.

%...... 省略若干行