ranch 源码分析（三）
上次讲到了ranch_conns_sup和ranch_acceptors_sup这2个ranch的核心模块，我们接着分析
首先查看ranch_conns_sup.erl
-module(ranch_conns_sup). %% API. -export([start_link/6]). -export([start_protocol/2]). -export([active_connections/1]). %...... 省略若干行 %% API. -spec start_link(ranch:ref(), conn_type(), shutdown(), module(), timeout(), module()) -> {ok, pid()}. start_link(Ref, ConnType, Shutdown, Transport, AckTimeout, Protocol) -> proc_lib:start_link(?MODULE, init, [self(), Ref, ConnType, Shutdown, Transport, AckTimeout, Protocol]). %...... 省略若干行 %% Supervisor internals. -spec init(pid(), ranch:ref(), conn_type(), shutdown(), module(), timeout(), module()) -> no_return(). init(Parent, Ref, ConnType, Shutdown, Transport, AckTimeout, Protocol) -> process_flag(trap_exit, true), ok = ranch_server:set_connections_sup(Ref, self()), MaxConns = ranch_server:get_max_connections(Ref), Opts = ranch_server:get_protocol_options(Ref), ok = proc_lib:init_ack(Parent, {ok, self()}), loop(#state{parent=Parent, ref=Ref, conn_type=ConnType, shutdown=Shutdown, transport=Transport, protocol=Protocol, opts=Opts, ack_timeout=AckTimeout, max_conns=MaxConns}, 0, 0, []). loop(State=#state{parent=Parent, ref=Ref, conn_type=ConnType, transport=Transport, protocol=Protocol, opts=Opts, max_conns=MaxConns}, CurConns, NbChildren, Sleepers) -> receive {?MODULE, start_protocol, To, Socket} -> try Protocol:start_link(Ref, Socket, Transport, Opts) of {ok, Pid} -> shoot(State, CurConns, NbChildren, Sleepers, To, Socket, Pid, Pid); {ok, SupPid, ProtocolPid} when ConnType =:= supervisor -> shoot(State, CurConns, NbChildren, Sleepers, To, Socket, SupPid, ProtocolPid); %...... 省略若干行 shoot(State=#state{ref=Ref, transport=Transport, ack_timeout=AckTimeout, max_conns=MaxConns}, CurConns, NbChildren, Sleepers, To, Socket, SupPid, ProtocolPid) -> case Transport:controlling_process(Socket, ProtocolPid) of ok -> ProtocolPid ! {shoot, Ref, Transport, Socket, AckTimeout}, put(SupPid, true), CurConns2 = CurConns + 1, if CurConns2 < MaxConns -> To ! self(), loop(State, CurConns2, NbChildren + 1, Sleepers); true -> loop(State, CurConns2, NbChildren + 1, [To|Sleepers]) end; {error, _} -> Transport:close(Socket), %% Only kill the supervised pid, because the connection's pid, %% when different, is supposed to be sitting under it and linked. exit(SupPid, kill), loop(State, CurConns, NbChildren, Sleepers) end. %...... 省略若干行
可以看到ranch_conns_sup不是一个典型的gen_tcp模块，
start_link/6启动init后直接使用了loop来循环，
init/7函数主要是获取了一些参数，
loop后等待消息（我们主要看start_protocol消息），loop函数根据start_protocol消息启动Protocol:start_link/4（用户编写的应用模块，这里表示echo_protocol），后面注意谁发这个消息给它
启动正常后，记录下ProtocolPid
继续查看ranch_acceptors_sup.erl
-module(ranch_acceptors_sup). -behaviour(supervisor). -export([start_link/4]). -export([init/1]). -spec start_link(ranch:ref(), non_neg_integer(), module(), any()) -> {ok, pid()}. start_link(Ref, NbAcceptors, Transport, TransOpts) -> supervisor:start_link(?MODULE, [Ref, NbAcceptors, Transport, TransOpts]). init([Ref, NbAcceptors, Transport, TransOpts]) -> ConnsSup = ranch_server:get_connections_sup(Ref), LSocket = case proplists:get_value(socket, TransOpts) of undefined -> TransOpts2 = proplists:delete(ack_timeout, proplists:delete(connection_type, proplists:delete(max_connections, proplists:delete(shutdown, proplists:delete(socket, TransOpts))))), case Transport:listen(TransOpts2) of {ok, Socket} -> Socket; {error, Reason} -> listen_error(Ref, Transport, TransOpts2, Reason) end; Socket -> Socket end, {ok, Addr} = Transport:sockname(LSocket), ranch_server:set_addr(Ref, Addr), Procs = [ {{acceptor, self(), N}, {ranch_acceptor, start_link, [ LSocket, Transport, ConnsSup ]}, permanent, brutal_kill, worker, []} || N <- lists:seq(1, NbAcceptors)], {ok, {{one_for_one, 1, 5}, Procs}}. -spec listen_error(any(), module(), any(), atom()) -> no_return(). listen_error(Ref, Transport, TransOpts2, Reason) -> error_logger:error_msg( "Failed to start Ranch listener ~p in ~p:listen(~p) for reason ~p (~s)~n", [Ref, Transport, TransOpts2, Reason, inet:format_error(Reason)]), exit({listen_error, Ref, Reason}).
这里进行最主要的操作有
打开端口Transport:listen/1开始监听端口
启动NbAcceptors个ranch_accetor:start_link进程等待连接，
接下来就是查看ranch_acceptor.erl
-module(ranch_acceptor). -export([start_link/3]). -export([loop/3]). -spec start_link(inet:socket(), module(), pid()) -> {ok, pid()}. start_link(LSocket, Transport, ConnsSup) -> Pid = spawn_link(?MODULE, loop, [LSocket, Transport, ConnsSup]), {ok, Pid}. -spec loop(inet:socket(), module(), pid()) -> no_return(). loop(LSocket, Transport, ConnsSup) -> _ = case Transport:accept(LSocket, infinity) of {ok, CSocket} -> case Transport:controlling_process(CSocket, ConnsSup) of ok -> %% This call will not return until process has been started %% AND we are below the maximum number of connections. ranch_conns_sup:start_protocol(ConnsSup, CSocket); {error, _} -> Transport:close(CSocket) end; %% Reduce the accept rate if we run out of file descriptors. %% We can't accept anymore anyway, so we might as well wait %% a little for the situation to resolve itself. {error, emfile} -> receive after 100 -> ok end; %% We want to crash if the listening socket got closed. {error, Reason} when Reason =/= closed -> ok end, flush(), ?MODULE:loop(LSocket, Transport, ConnsSup). flush() -> receive Msg -> error_logger:error_msg( "Ranch acceptor received unexpected message: ~p~n", [Msg]), flush() after 0 -> ok end.
当客户端端连接，accept返回ok，ranch_conns_sup:start_protocol/2发送{?MODULE, start_protocol, self(), Socket}给ConnsSup，
-module(ranch_conns_sup). %% API. -export([start_link/6]). -export([start_protocol/2]). -export([active_connections/1]). %%.......省略若干行 -spec start_protocol(pid(), inet:socket()) -> ok. start_protocol(SupPid, Socket) -> SupPid ! {?MODULE, start_protocol, self(), Socket}, receive SupPid -> ok end. %%.......省略若干行
启动Protocol:start_link/4的详细过程，参考上面的ranch_conns_sup分析
好，这个时候基本ranch的大致结构就分析出来了，还有一些其他的细节留以后慢慢添加。
