使用 Nginx + Lua 实现配置文件的默认选择

业务场景

当前业务需求是，当前系统中，针对项目添加不同的版本配置，并可选的设定为默认配置项(即读取项目而不传入版本号，则读取默认版本信息)

原计划使用python实现当前场景，但考虑后期并发问题，可能在python读写数据库或者缓存对服务器产生压力。而考虑以纯静态文件方式来解决后期并发问题，故选择了使用nginx+Lua来实现业务场景。
对于接口的请求，以文件目录结构方式访问， http://xxx.com/project_id/version ，可无需输入version来读取默认配置版本信息。
对于存在的文件，直接nginx读取，对于不存在的路径，则由程序处理

使用python

@mod.route('<path:subpath>', methods=['GET', 'POST'])
def configs(subpath=None):
    parts = urllib.parse.unquote(subpath).split('/')
    project_id = parts[0] if len(parts) > 0 else None
    version = parts[1] if len(parts) > 1 else None

    if not os.path.exists(os.path.join(static_path, project_id)):
        return Response("None")
    path = os.path.join(static_path, project_id, version)
    if not os.path.exists(path):
        path = os.path.join(static_path, project_id, 'index')
    else:
        path = os.path.join(static_path, project_id, version, 'index')

    with open(path, 'r', encoding='utf-8') as f:
        config_info = f.readlines()
    return Response("\n".join(config_info), mimetype=ResHelper.JSON)

server  {
    listen  80;
    server_name  static.com;
    lua_code_cache on;
    location  /  {
        default_type application/json;
        charset utf-8;
        add_header Content-Type "application/json; charset=utf-8";
        try_files $uri $uri/ @missing_slash;

        root E:\\data\\static\\;
        index index;
    }
    # 内部重定向处理器，处理缺少尾部斜杠的路径
    location @missing_slash {
        internal;
        add_header Content-Type "application/json; charset=utf-8";
        proxy_pass http://localhost:5001/configfile$uri;
        include proxy.conf;
    }
}

Lua方式

server  {
    listen  80;
    server_name  static.com;
    lua_code_cache on;
    location  /  {
        default_type application/json;
        charset utf-8;
        add_header Content-Type "application/json; charset=utf-8";
        try_files $uri $uri/ @missing_slash;

        root E:\\data\\static\\;
        index index;
    }
    # 内部重定向处理器，处理缺少尾部斜杠的路径
    location @missing_slash {
        internal;
        add_header Content-Type "application/json; charset=utf-8";

        # 定义一个变量来保存 location 的 root 路径
        set $root_path "E:\\data\\static\\";
        # 使用 lua脚本来校验请求路径
        content_by_lua_file lua/a.lua;
    }
}

使用lua 判断目录是否存在，存在读取对应的文件内容并返回给接口

function isFile(name)
    if type(name)~="string" then return false end
    local f = io.open(name)
    if f then
        f:close()
        return true
    end
    return false
end

function file_exists_v2(file)
  -- some error codes:
  -- 13 : EACCES - Permission denied
  -- 17 : EEXIST - File exists
  -- 20	: ENOTDIR - Not a directory
  -- 21	: EISDIR - Is a directory
  --
  local isok, errstr, errcode = os.rename(file, file)
  if isok == nil then
     if errcode == 13 then 
        -- Permission denied, but it exists
        return true
     end
     return false
  end
  return true
end

local root_path = ngx.var.root_path
print("Root Path: ", root_path)

function readFiles(projectid, version)
	
	print("Three segments: ", projectid, ", ", version)
	print("", root_path , appid, file_exists_v2(root_path .. projectid .. '/') )
	if file_exists_v2(root_path .. projectid) == false then
		ngx.say('{"code":404}')
	else
		print("存在目录" .. root_path .. projectid)
		local idx_path = root_path .. projectid .. '/index'
		-- --目录存在，判断版本是否存在
		if file_exists_v2(root_path .. projectid .. '/' .. version) then
		--	-- 读取 index
			idx_path = root_path .. projectid .. '/' .. version .. '/index'
		end
		print(idx_path)
		print(isFile(idx_path))
		local file = io.open(idx_path, "r")
		--		--			 
		-- 读取文件内容
		local content = file:read("*all")
		ngx.say(content)
		file:close()
	end
end
--
-- 获取请求的 URI 路径
local uri = ngx.var.uri
print(uri)
 --分割 URI 路径
local segments = {}
for segment in string.gmatch(uri, "[^/]+") do
	table.insert(segments, segment)
end
 --根据路径长度赋值变量
if #segments == 1 then
	local var1 = segments[1]
	readFiles(var1, nil)
elseif #segments >= 2 then
	local var1 = segments[1]
	local var2 = segments[2]
	readFiles(var1, var2)
end