ranch源码阅读

ranch

整体理解

从整体上的话，ranch主要是三层的监控树

• 第一层 ranch_sup，负责整个应用的启动，启动了ranch_server进程，它管理了整个应用的配置和连接数据
• 第二层 ranch_listener_sup，负责连接的管理
• 第三层 ranch_conns_sup和ranch_acceptors_sup，这两个分别用来处理新的连接和获得新的连接
  
  当然最底层的ranch_acceptor是应用中的重要角色，每当有新的连接，都会把控制权交给ranch_conns_sup，由它统一管理

ranch.app

启动模块为ranch_app,说明需要找到ranch_app.erl文件去启动应用

ranch_app.erl

根据参数启动测试的功能，主要启动了一个ranch_sup监控进程

ranch_sup.erl

新建一个名为ranch_server的ets表，同时启动并监控ranch_server进程，策略为one_for_one

ranch_server.erl

启动了一个进程，管理ranch_server这个ets表，提供多个接口

set_new_listener_opts：设置监听进程的参数

set_connections_sup：增加新的连接进程的监控进程Pid，并且对该进程进行monitor监视，把{MonitorRef, Pid}添加到#state.monitors中

set_listener_sup：增加一个监听进程的监控进程Pid，并且对该进程进行monitor监视，并且把{MonitorRef, Pid}添加到#state.monitors中

set_addr：在ets中记录地址

set_max_conns：设置最大连接数量

set_trans_opts：设置传输协议参数

set_proto_opts：设置协议参数

到此为止，ranch应用的准备工作已经结束，剩下的就差外部的调用了

---

ranch.erl

ranch应用的调用模块，通过start_listener/6来初始化ranch的功能模块，给它提供功能参数，其中有一个Transport参数，是ranch的协议模块名，要么是ranch_ssl,要么就是ranch_tcp，先在ranch_sup下面启动了一个ranch_listener_sup进程，该进程做了什么，接下来将详细介绍，至少在这里我们知道，ranch的正式使用由ranch_listener_sup进程启动开始。

-spec start_listener(ref(), module(), any(), module(), any())
	-> supervisor:startchild_ret().
start_listener(Ref, Transport, TransOpts, Protocol, ProtoOpts) ->
	NumAcceptors = proplists:get_value(num_acceptors, TransOpts, 10),
	start_listener(Ref, NumAcceptors, Transport, TransOpts, Protocol, ProtoOpts).

-spec start_listener(ref(), non_neg_integer(), module(), any(), module(), any())
	-> supervisor:startchild_ret().
start_listener(Ref, NumAcceptors, Transport, TransOpts, Protocol, ProtoOpts)
		when is_integer(NumAcceptors) andalso is_atom(Transport)
		andalso is_atom(Protocol) ->
	_ = code:ensure_loaded(Transport),
	case erlang:function_exported(Transport, name, 0) of
		false ->
			{error, badarg};
		true ->
			Res = supervisor:start_child(ranch_sup, child_spec(Ref, NumAcceptors,
					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,
			maybe_started(Res)
	end.

-spec child_spec(ref(), module(), any(), module(), any())
	-> supervisor:child_spec().
child_spec(Ref, Transport, TransOpts, Protocol, ProtoOpts) ->
	NumAcceptors = proplists:get_value(num_acceptors, TransOpts, 10),
	child_spec(Ref, NumAcceptors, Transport, TransOpts, Protocol, ProtoOpts).

-spec child_spec(ref(), non_neg_integer(), module(), any(), module(), any())
	-> supervisor:child_spec().
child_spec(Ref, NumAcceptors, Transport, TransOpts, Protocol, ProtoOpts)
		when is_integer(NumAcceptors) andalso is_atom(Transport)
		andalso is_atom(Protocol) ->
	{{ranch_listener_sup, Ref}, {ranch_listener_sup, start_link, [
		Ref, NumAcceptors, Transport, TransOpts, Protocol, ProtoOpts
	]}, permanent, infinity, supervisor, [ranch_listener_sup]}.

ranch_listener_sup.erl

该监控进程启动时，主动调用ranch_server:set_listener_sup/2，将自己的信息记录在ets中并且被ranch_server监控，它下面还顺序启动了ranch_conns_sup和ranch_acceptors_sup，策略是rest_for_one，因为ranch_conns_sup是负责监控连接的进程，而ranch_acceptors_sup是监控消息的进程，ranch_conns_sup死掉之后，说明连接都断开了，ranch_acceptors_sup下面的进程也就无法运行，必须等ranch_conns_sup重启成功后才能正常工作。

ranch_conns_sup.erl

该模块并不是supervisor行为，不过作者手动写了一个类似supervisor的东西，启动时主动调用ranch_server:set_connections_sup/2记录自身的信息，同时通过ranch_server获取相应的一些连接参数，其中用到了proc_lib:init_ack/2用于响应proc_lib:start_link/3，实现同步启动进程，做到和gen_server一样的效果，接着开始一个循环函数loop/4，用来处理消息，下面列出主要的消息处理

{?MODULE, start_protocol, T, Socket}：参数中To为ranch_acceptor模块的进程pid，而Socket是ranch_acceptor接收到的客户端socket，启动一个调用Protocol:start_link/4启动一个进程，这个Protocol是用户实现的回调模块，通常是socket消息的接收处理进程，就像例子中的echo_protocol.erl或者reverse_protocol.erl这两个部分，如果启动成功，将会调用shoot/8来修改回调模块的Socket的控制进程，即socket的消息将发送到哪个进程在这里决定，修改之后，将回复回调部分进程一个{shoot, Ref, Transport, Socket, AckTimeout}消息，接着检查当前连接数量是否达到配置中的MaxConns，如果达到了最大连接数的话则把连接加入到等待连接列表中，同时增加子连接数量，继续循环loop/4

{?MODULE, active_connections, To, Tag}：To连接进程获取当前连接列表

{remove_connection, Ref, Pid}：移除某个连接进程

-spec init(pid(), ranch:ref(), module(), module()) -> no_return().
init(Parent, Ref, Transport, Protocol) ->
	process_flag(trap_exit, true),
	ok = ranch_server:set_connections_sup(Ref, self()),
	MaxConns = ranch_server:get_max_connections(Ref),
	TransOpts = ranch_server:get_transport_options(Ref),
	ConnType = proplists:get_value(connection_type, TransOpts, worker),
	Shutdown = proplists:get_value(shutdown, TransOpts, 5000),
	AckTimeout = proplists:get_value(ack_timeout, TransOpts, 5000),
	ProtoOpts = 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=ProtoOpts, 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);
				Ret ->
					To ! self(),
					error_logger:error_msg(
						"Ranch listener ~p connection process start failure; "
						"~p:start_link/4 returned: ~999999p~n",
						[Ref, Protocol, Ret]),
					Transport:close(Socket),
					loop(State, CurConns, NbChildren, Sleepers)
			catch Class:Reason ->
				To ! self(),
				error_logger:error_msg(
					"Ranch listener ~p connection process start failure; "
					"~p:start_link/4 crashed with reason: ~p:~999999p~n",
					[Ref, Protocol, Class, Reason]),
				loop(State, CurConns, NbChildren, Sleepers)
			end;
		{?MODULE, active_connections, To, Tag} ->
			To ! {Tag, CurConns},
			loop(State, CurConns, NbChildren, Sleepers);
		%% Remove a connection from the count of connections.
		{remove_connection, Ref, Pid} ->
			case put(Pid, removed) of
				active ->
					loop(State, CurConns - 1, NbChildren, Sleepers);
				remove ->
					loop(State, CurConns, NbChildren, Sleepers);
				undefined ->
					_ = erase(Pid),
					loop(State, CurConns, NbChildren, Sleepers)
			end;
		%% Upgrade the max number of connections allowed concurrently.
		%% We resume all sleeping acceptors if this number increases.
		{set_max_conns, MaxConns2} when MaxConns2 > MaxConns ->
			_ = [To ! self() || To <- Sleepers],
			loop(State#state{max_conns=MaxConns2},
				CurConns, NbChildren, []);
		{set_max_conns, MaxConns2} ->
			loop(State#state{max_conns=MaxConns2},
				CurConns, NbChildren, Sleepers);
		%% Upgrade the protocol options.
		{set_opts, Opts2} ->
			loop(State#state{opts=Opts2},
				CurConns, NbChildren, Sleepers);
		{'EXIT', Parent, Reason} ->
			terminate(State, Reason, NbChildren);
		{'EXIT', Pid, Reason} when Sleepers =:= [] ->
			case erase(Pid) of
				active ->
					report_error(Ref, Protocol, Pid, Reason),
					loop(State, CurConns - 1, NbChildren - 1, Sleepers);
				removed ->
					report_error(Ref, Protocol, Pid, Reason),
					loop(State, CurConns, NbChildren - 1, Sleepers);
				undefined ->
					loop(State, CurConns, NbChildren, Sleepers)
			end;
		%% Resume a sleeping acceptor if needed.
		{'EXIT', Pid, Reason} ->
			case erase(Pid) of
				active when CurConns > MaxConns ->
					report_error(Ref, Protocol, Pid, Reason),
					loop(State, CurConns - 1, NbChildren - 1, Sleepers);
				active ->
					report_error(Ref, Protocol, Pid, Reason),
					[To|Sleepers2] = Sleepers,
					To ! self(),
					loop(State, CurConns - 1, NbChildren - 1, Sleepers2);
				removed ->
					report_error(Ref, Protocol, Pid, Reason),
					loop(State, CurConns, NbChildren - 1, Sleepers);
				undefined ->
					loop(State, CurConns, NbChildren, Sleepers)
			end;
		{system, From, Request} ->
			sys:handle_system_msg(Request, From, Parent, ?MODULE, [],
				{State, CurConns, NbChildren, Sleepers});
		%% Calls from the supervisor module.
		{'$gen_call', {To, Tag}, which_children} ->
			Children = [{Protocol, Pid, ConnType, [Protocol]}
				|| {Pid, Type} <- get(),
				Type =:= active orelse Type =:= removed],
			To ! {Tag, Children},
			loop(State, CurConns, NbChildren, Sleepers);
		{'$gen_call', {To, Tag}, count_children} ->
			Counts = case ConnType of
				worker -> [{supervisors, 0}, {workers, NbChildren}];
				supervisor -> [{supervisors, NbChildren}, {workers, 0}]
			end,
			Counts2 = [{specs, 1}, {active, NbChildren}|Counts],
			To ! {Tag, Counts2},
			loop(State, CurConns, NbChildren, Sleepers);
		{'$gen_call', {To, Tag}, _} ->
			To ! {Tag, {error, ?MODULE}},
			loop(State, CurConns, NbChildren, Sleepers);
		Msg ->
			error_logger:error_msg(
				"Ranch listener ~p received unexpected message ~p~n",
				[Ref, Msg]),
			loop(State, CurConns, NbChildren, Sleepers)
	end.

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, active),
			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),
			To ! self(),
			loop(State, CurConns, NbChildren, Sleepers)
	end.

ranch_acceptors_sup.erl

从ranch_server中获取ranch_conns_sup的进程，并且获取监听参数TransOpts，如果ranch_server中尚未有监听socket，则启动监听socket，接着把监听socket记录到ranch_server中，启动一个ranch_acceptor子进程。

ranch_acceptor.erl

启动一个loop/3循环，当接收到客户端的socket之后，把socket的控制进程改为连接监控进程ranch_conns_sup，连接监控进程中有对应的一些消息处理，接着调用ranch_conns_sup:start_protocol/2发送{?MODULE, start_protocol, self(), Socket},ranch_conns_sup进程自身对该消息进行处理，详情看ranch_conns_sup.erl的介绍，至此，ranch的监听端口的工作都已经准备完毕，（发现还有部分忽略了，需要实现ranch_protocol行为才能处理客户端消息的）现在就差客户端的连接进来了。

-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} ->
			error_logger:warning_msg("Ranch acceptor reducing accept rate: out of file descriptors~n"),
			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).