# Ngx\_lua post data error/bug? **URL:** \ **Category:** NGINX\ **Created:** [October 21, 2011, 8:07pm UTC](https://www.ruby-forum.com/t/ngx-lua-post-data-error-bug/213058 "2011-10-21T20:07:11Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [October 21, 2011, 8:07pm UTC](https://www.ruby-forum.com/t/ngx-lua-post-data-error-bug/213058/1 "2011-10-21T20:07:11Z")
This is a follow on from: [http://mailman.nginx.org/pipermail/nginx/2011-October/029905.html](http://mailman.nginx.org/pipermail/nginx/2011-October/029905.html) The conditional statements take care of the basic error but what happens is that when “post” requests match any of the test regexes, an error is thrown … “lua handler aborted: runtime error: attempt to yield across metamethod/C-call boundary blah, blah, blah”. It appears this is due to a limitation in Lua 5.1 and this yeilding is a major item for Lua 5.2. However, trying to build Nginx with the lua module against Lua 5.2 fails… ``` /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx_http_lua_conf.c ``` /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c: In function ‘ngx\_http\_lua\_new\_thread’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:189: error: ‘LUA\_GLOBALSINDEX’ undeclared (first use in this function) /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:189: error: (Each undeclared identifier is reported only once /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:189: error: for each function it appears in.) /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c: In function ‘ngx\_http\_lua\_del\_thread’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:228: warning: implicit declaration of function ‘lua\_getfenv’ /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:234: warning: implicit declaration of function ‘lua\_setfenv’ /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c: In function ‘init\_ngx\_lua\_globals’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:507: error: ‘LUA\_GLOBALSINDEX’ undeclared (first use in this function) /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c: In function ‘ngx\_http\_lua\_discard\_bufs’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:544: warning: unused parameter ‘pool’ /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c: In function ‘ngx\_http\_lua\_set\_multi\_value\_table’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_util.c:1167: warning: implicit declaration of function ‘lua\_objlen’ make[1]: \*\*\* [objs/addon/src/ngx\_http\_lua\_util.o] Error 1 make[1]: \*\*\* Waiting for unfinished jobs… /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_conf.c: In function ‘ngx\_http\_lua\_merge\_loc\_conf’: /usr/src/redhat/BUILD/nginx-1.0.8/ngx-lua-module-0.31rc17-0/src/ngx\_http\_lua\_conf.c:95: warning: unused parameter ‘cf’ make[1]: Leaving directory `/usr/src/redhat/BUILD/nginx-1.0.8’ make: \*\*\* [build] Error 2 error: Bad exit status from /var/tmp/rpm-tmp.63523 (%build) The upshot is that perhaps only LuaJIT 2.0 can be used for all features in recent versions of ngx\_lua. Luckily, I took a backup of my server state so I’ll be rolling back and commenting out the “post” block. ---
**Author:** ![Nginx\_U](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dec6dc/32.png) [@Nginx\_U](https://www.ruby-forum.com/u/Nginx_U)\ **Post date:** [October 21, 2011, 9:43pm UTC](https://www.ruby-forum.com/t/ngx-lua-post-data-error-bug/213058/2 "2011-10-21T21:43:45Z")
On 21 October 2011 21:06, Nginx U. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > This is a follow on from: > [lua\_need\_request\_body ... limitations?](http://mailman.nginx.org/pipermail/nginx/2011-October/029905.html) > > The conditional statements take care of the basic error but what > happens is that when “post” requests match any of the test regexes, an > error is thrown … > “lua handler aborted: runtime error: attempt to yield across > metamethod/C-call boundary blah, blah, blah”. > > It appears this is due to a limitation in Lua 5.1 … Testing shows that the error is generated because of the ‘dofile(“/etc/nginx/regex\_rules.lua”)’ line. I.E., when the regex rules are placed directly in the access\_by\_lua\_file, a hit on a regex is processed as expected. When the rules are included using the dofile function, a hit on a regex results in the "attempt to yield across ---
**Author:** ![Nginx\_U](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dec6dc/32.png) [@Nginx\_U](https://www.ruby-forum.com/u/Nginx_U)\ **Post date:** [October 22, 2011, 3:26am UTC](https://www.ruby-forum.com/t/ngx-lua-post-data-error-bug/213058/3 "2011-10-22T03:26:08Z")
On Sat, Oct 22, 2011 at 3:43 AM, Nginx U. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Testing shows that the error is generated because of the > ‘dofile(“/etc/nginx/regex\_rules.lua”)’ line. Lua’s “dofile” builtin is implemented as a C function in both Lua 5.1 and LuaJIT 2.0. And when you call ngx.location.capture or ngx.exec or ngx.exit or ngx.req.read\_body or something like those in the regex\_rules.lua, it’ll effectively initiate a coroutine yield and that yield will run across C function boundary, which is disallowed. I think it’s more efficient to use Lua modules and the “require” builtin because dofile will load the .lua file from disk at _every_ request and it’s quite costy while “require” will only load the .lua module file only once unless lua\_code\_cache is turned off. Here is an example, ``` -- regex_rules.lua module("regex_rules", package.seeall) function check() ngx.req.read_body() -- other processing goes here... end # nginx.conf lua_package_path ``` “/path/to/regex\_rules.lua’s-parent-directory/?.lua;;” server { location /foo { access\_by\_lua ’ local regex\_rules = require “regex\_rules” regex\_rules.check() '; # content handler config goes here… } } BTW, compatibility with Lua 5.2 is not maintained by ngx\_lua (yet). Regards, -agentzh ---
**Author:** ![Nginx\_U](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dec6dc/32.png) [@Nginx\_U](https://www.ruby-forum.com/u/Nginx_U)\ **Post date:** [October 22, 2011, 8:31am UTC](https://www.ruby-forum.com/t/ngx-lua-post-data-error-bug/213058/4 "2011-10-22T08:31:49Z")
On 22 October 2011 04:25, agentzh [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > yield will run across C function boundary, which is disallowed. > ngx.req.read\_body() > '; > # content handler config goes here… > } > } > > BTW, compatibility with Lua 5.2 is not maintained by ngx\_lua (yet). Magic … Works perfectly. You are a legend!