String operation inside content_by_lua returns error

maanas · 2012-10-28T02:39:31+00:00

Hello! On Mon, Jun 30, 2014 at 4:04 AM, Stefan Parvu wrote: > > Do we have any MongoDB support for OpenResty right now ? Or still one will > requir...

String operation inside content_by_lua returns error

maanas

I m trying to do some string operation inside content by lua

content_by_lua '

local app = ngx.var.arg_app or "none"

local resp = ngx.location.capture("/session?app="..app)

if resp.status == 200 then

_, _, cnt, uid, status = string.find(resp.body, "%[%{\"cnt\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]")

ngx.print(resp.body)

end';

basically trying to decode a fix json. I not going via cjson route as the json in my case will be fixed. I have check this code on command line it works

Luajit

> s = '[{"cnt":10,"uid":11,"status":12}]'

> _, _, no, uid, status = string.find(s, "%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]")

> print (no, uid, status)

10 11 12

But when i run in ngnix i get this error. I suspect this has to do with qoutes. Any way i can qoute the string in different way.

2012/10/27 22:39:02 [error] 20335#0: *1 failed to load Lua inlined code: [string "content_by_lua"]:5: ')' expected near 'no', client:---

maanas

I am finally able to get this done using this

i m not sure whether it is correct way

_, _, no, uid, status = string.find(resp.body, [[%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]%s*]])

Can any one please comment on this.

On Sunday, October 28, 2012 12:09:31 AM UTC+5:30, Maanas wrote:

I m trying to do some string operation inside content by lua

content_by_lua '
local app = ngx.var.arg_app or "none"
local resp = ngx.location.capture("/session?app="..app)
if resp.status == 200 then
_, _, cnt, uid, status = string.find(resp.body, "%[%{\"cnt\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]")
ngx.print(resp.body)
end';

basically trying to decode a fix json. I not going via cjson route as the json in my case will be fixed. I have check this code on command line it works

Luajit
> s = '[{"cnt":10,"uid":11,"status":12}]'
> _, _, no, uid, status = string.find(s, "%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]")
> print (no, uid, status)
10 11 12

But when i run in ngnix i get this error. I suspect this has to do with qoutes. Any way i can qoute the string in different way.
2012/10/27 22:39:02 [error] 20335#0: *1 failed to load Lua inlined code: [string "content_by_lua"]:5: ')' expected near 'no', client:---

jason.dusek

2012/10/27 Maanas <ma...@maanas.co>:
> I am finally able to get this done using this
> i m not sure whether it is correct way
> _, _, no, uid, status = string.find(resp.body,
> [[%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]%s*]])

I wonder what happend if you remove all the backslashes...

--
Jason Dusek
pgp // solidsnack // C1EBC57DC55144F35460C8DF1FD4C6C1FED18A2B

maanas

It works. I added back slashes as tried on cmd line using " but was not working in ngnix. Now with [[ .. ]] it do works

here is the updated one.

_, _, no, uid, status = string.find(s, [[%[%{"no":(%d+),"uid":(%d+),"status":(%d+)%}%]%s*]])

I m not sure how good this. is any comment on that. I have no idea where this create any problem in production server?

On Sunday, October 28, 2012 12:29:57 AM UTC+5:30, Jason Dusek wrote:

2012/10/27 Maanas <maa...@maanas.co>:
> I am finally able to get this done using this
> i m not sure whether it is correct way
> _, _, no, uid, status = string.find(resp.body,
> [[%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]%s*]])

I wonder what happend if you remove all the backslashes...

--
Jason Dusek
pgp // solidsnack // C1EBC57DC55144F35460C8DF1FD4C6C1FED18A2B

agentzh

Hello!

On Sat, Oct 27, 2012 at 12:03 PM, Maanas wrote:
> It works. I added back slashes as tried on cmd line using " but was not
> working in ngnix.

That's because you're inlining Lua code in an Nginx literal string
where Nginx literal strings also treat backslashes specially. See the
note in ngx_lua's documentation here:

    http://wiki.nginx.org/HttpLuaModule#Special_PCRE_Sequences

Basically you need to escape every occurrence of \ for the Nginx
string. So it's recommended to use the content_by_lua_file directive
and specify an external .lua file to prevent such pitfalls with
inlined Lua code.

Best regards,
-agentzh

jason.dusek

2012/10/27 Maanas <ma...@maanas.co>:
> On Sunday, October 28, 2012 12:29:57 AM UTC+5:30, Jason Dusek wrote:
>> 2012/10/27 Maanas <maa...@maanas.co>:
>>> I am finally able to get this done using this
>>> i m not sure whether it is correct way
>>> _, _, no, uid, status = string.find(resp.body,
>>> [[%[%{\"no\":(%d+),\"uid\":(%d+),\"status\":(%d+)%}%]%s*]])
>>
>> I wonder what happend if you remove all the backslashes...
>
> It works. I added back slashes as tried on cmd line using " but was not
> working in ngnix. Now with [[ .. ]] it do works
> here is the updated one.
> _, _, no, uid, status = string.find(s,
> [[%[%{"no":(%d+),"uid":(%d+),"status":(%d+)%}%]%s*]])
>
> I m not sure how good this. is any comment on that. I have no idea where
> this create any problem in production server?

I wonder if the backslashes are not even pass through to Lua;
but in fact consumed by Nginx. Since your string is [[]] quoted,
the bare quotes inside aren't a problem.

--
Jason Dusek
pgp // solidsnack // C1EBC57DC55144F35460C8DF1FD4C6C1FED18A2B


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