Skynet源码赏析三 | 服务启动

struct snlua * snlua_create(void) {
    //初始化snlua结构
	struct snlua * l = skynet_malloc(sizeof(*l));
	memset(l,0,sizeof(*l));
	l->mem_report = MEMORY_WARNING_REPORT;
    ...
    //初始化一个lua虚拟机
	l->L = lua_newstate(lalloc, l);
    ...
	return l;
}

int snlua_init(struct snlua *l, struct skynet_context *ctx, const char * args) {
    ...
    //指定回掉函数
	skynet_callback(ctx, l , launch_cb);
    //取本地服务的句柄
	const char * self = skynet_command(ctx, "REG", NULL);
   	uint32_t handle_id = strtoul(self+1, NULL, 16);
	// it must be first message
    //发送第一条消息，在launc_cb可见
	skynet_send(ctx, 0, handle_id, PTYPE_TAG_DONTCOPY,0, tmp, sz);
	return 0;
}

static int init_cb(struct snlua *l, struct skynet_context *ctx, const char * args, size_t sz) {
	lua_State *L = l->L;
	l->ctx = ctx;
	lua_gc(L, LUA_GCSTOP, 0);
    ...
    //LUA_PATH：Lua搜索路径，在config.lua_path指定。
	const char *path = optstring(ctx, "lua_path","./lualib/?.lua;./lualib/?/init.lua");
	lua_pushstring(L, path);
	lua_setglobal(L, "LUA_PATH");

    //LUA_CPATH：C模块的搜索路径，在config.lua_cpath指定。
	const char *cpath = optstring(ctx, "lua_cpath","./luaclib/?.so");
	lua_pushstring(L, cpath);
	lua_setglobal(L, "LUA_CPATH");

    //LUA_SERVICE：Lua服务的搜索路径，在config.luaservice指定。
	const char *service = optstring(ctx, "luaservice", "./service/?.lua");
	lua_pushstring(L, service);
	lua_setglobal(L, "LUA_SERVICE");

    //LUA_PRELOAD：预加载脚本，这些脚本会在所有服务开始之前执行，可以用它来初始化一些全局的设置。执行loader.lua，把要执行的脚本传进去，由loader去加载执行，skynet初始执行bootstrap.lua。
    const char *preload = skynet_command(ctx, "GETENV", "preload");
	lua_pushstring(L, preload);
	lua_setglobal(L, "LUA_PRELOAD");
	const char * loader = optstring(ctx, "lualoader", "./lualib/loader.lua");

	int r = luaL_loadfile(L,loader);
    ...
	lua_pushlstring(L, args, sz);
    //执行lua脚本，调用脚本里 skynet.start的地方
	r = lua_pcall(L,1,0,1);
	if (r != LUA_OK) {
		skynet_error(ctx, "lua loader error : %s", lua_tostring(L, -1));
		report_launcher_error(ctx);
		return 1;
	}
    ...
	lua_gc(L, LUA_GCRESTART, 0);

	return 0;
}

function skynet.newservice(name, ...)
	return skynet.call(".launcher", "lua" , "LAUNCH", "snlua", name, ...)
end

--launcher.lua
local function launch_service(service, ...)
	local param = table.concat({...}, " ")
    --创建一个服务，并返回服务句柄
	local inst = skynet.launch(service, param)
	local session = skynet.context()
    --取一个resonse闭包，先存起来，等skynet.start返回再调用。
	local response = skynet.response()
	if inst then
		services[inst] = service .. " " .. param
		instance[inst] = response
		launch_session[inst] = session
	else
		response(false)
		return
	end
	return inst
end

function command.LAUNCH(_, service, ...)
	launch_service(service, ...)
	return NORET
end

function skynet.start(start_func)
	c.callback(skynet.dispatch_message)
	init_thread = skynet.timeout(0, function()
		skynet.init_service(start_func)
		init_thread = nil
	end)
end

function skynet.init_service(start)
	local function main()
		skynet_require.init_all()
		start()
	end
	local ok, err = xpcall(main, traceback)
	if not ok then
		skynet.error("init service failed: " .. tostring(err))
		skynet.send(".launcher","lua", "ERROR")
		skynet.exit()
	else
		skynet.send(".launcher","lua", "LAUNCHOK")
	end
end

function command.LAUNCHOK(address)
	-- init notice
	local response = instance[address]
	if response then
		response(true, address)
		instance[address] = nil
		launch_session[address] = nil
	end

	return NORET
end

function skynet.call(addr, typename, ...)
	local tag = session_coroutine_tracetag[running_thread]
	if tag then
		c.trace(tag, "call", 2)
		c.send(addr, skynet.PTYPE_TRACE, 0, tag)
	end

	local p = proto[typename]
	local session = c.send(addr, p.id , nil , p.pack(...))
	if session == nil then
		error("call to invalid address " .. skynet.address(addr))
	end
	return p.unpack(yield_call(addr, session))
end

ret = c.send(co_address, skynet.PTYPE_RESPONSE, co_session, pack(...))

local function raw_dispatch_message(prototype, msg, sz, session, source)
	-- skynet.PTYPE_RESPONSE = 1, read skynet.h
	if prototype == 1 then
		local co = session_id_coroutine[session]
		if co == "BREAK" then
			session_id_coroutine[session] = nil
		elseif co == nil then
			unknown_response(session, source, msg, sz)
		else
			local tag = session_coroutine_tracetag[co]
			if tag then c.trace(tag, "resume") end
			session_id_coroutine[session] = nil
            -- 在这一步重新调用协程函数
			suspend(co, coroutine_resume(co, true, msg, sz))
		end
        ...
end