lua 读取redis 中的图片缓存的问题

sarowlwp

原有系统将每天夜里生成的验证码图片缓存起来，现在想尝试通过 lua +nginx直接读取图片返回，报错，春哥能看下么？非常感谢

lua entry thread aborted: runtime error: [string "content_by_lua"]:12: attempt to perform arithmetic on a string value

stack traceback:

coroutine 0:

[string "content_by_lua"]: in function <[string "content_by_lua"]:1>, client: 192.168.122.1, server: www.ngxtest.com, request: "GET /testredisimg HTTP/1.1", host: "192.168.122.130"

local ok,err = instance:connect("192.168.230.44","15231");

if not ok then

ngx.log(ngx.ERR,err);

ngx.exit(ngx.HTTP_SERVICE_UNAVAILABLE);

end

local vcodestr = instance:srandmember("vc:ENGLISH_WORD420130808");

local image = instance:getbit("vc:"+vcodestr)

instance:close();

ngx.say(image)

agentzh

Hello!

On Thu, Aug 8, 2013 at 2:08 AM, 刘文平 wrote:
> 原有系统将每天夜里生成的验证码图片缓存起来，现在想尝试通过 lua +nginx直接读取图片返回，报错，春哥能看下么？非常感谢
>
> lua entry thread aborted: runtime error: [string "content_by_lua"]:12:
> attempt to perform arithmetic on a string value

这个 Lua 错误是说你尝试对 Lua 字符串进行算术运算（比如加减乘除之类）。看下面这个命令行上的示例：

    $ luajit -e 'print("a" + "b")'
    luajit: (command line):1: attempt to perform arithmetic on a string value
    stack traceback:
    (command line):1: in main chunk
    [C]: at 0x00404b30

>
[...]
>                         local vcodestr =
> instance:srandmember("vc:ENGLISH_WORD420130808");
>                         local image = instance:getbit("vc:"+vcodestr)

显然，你上面这一行代码不符合 Lua 语法。在 Lua 语言中，字符串拼接运算符是 .. 而不是 +. 建议首先仔细阅读 Lua 5.1
语言手册，熟悉 Lua 的基本语法：

    http://www.lua.org/manual/5.1/manual.html

Regards,
-agentzh