others-how to solve the `module not found` error when running a lua script in openresty?

1. Problem

Here is the error message:

/usr/local/openresty/nginx/sbin/nginx -c /Users/bswen/lua-projects/openresty-demo/conf/nginx.conf -g daemon off; pid '/Users/bswen/lua-projects/openresty-demo/nginx.pid';
2022/06/01 14:28:41 [error] 17956#0: *1 lua entry thread aborted: runtime error: content_by_lua(nginx-listen-30086.conf:44):3: module 'resty.jwt' not found:
    no field package.preload['resty.jwt']

    no file '/Users/bswen/lua-projects/openresty-demo/src/resty/jwt.lua'
    no file '/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/resty/jwt.lua'
    no file '/usr/local/openresty/site/lualib/resty/jwt.ljbc'
    no file '/usr/local/openresty/site/lualib/resty/jwt/init.ljbc'
    no file '/usr/local/openresty/lualib/resty/jwt.ljbc'
    no file '/usr/local/openresty/lualib/resty/jwt/init.ljbc'
    no file '/usr/local/openresty/site/lualib/resty/jwt.lua'
    no file '/usr/local/openresty/site/lualib/resty/jwt/init.lua'
    no file '/usr/local/openresty/lualib/resty/jwt.lua'
    no file '/usr/local/openresty/lualib/resty/jwt/init.lua'
    no file './resty/jwt.lua'
    no file '/usr/local/openresty/luajit/share/luajit-2.1.0-beta3/resty/jwt.lua'
    no file '/usr/local/share/lua/5.1/resty/jwt.lua'
    no file '/usr/local/share/lua/5.1/resty/jwt/init.lua'
    no file '/usr/local/openresty/luajit/share/lua/5.1/resty/jwt.lua'
    no file '/usr/local/openresty/luajit/share/lua/5.1/resty/jwt/init.lua'
    no file '/usr/local/openresty/site/lualib/resty/jwt.so'
    no file '/usr/local/openresty/lualib/resty/jwt.so'
    no file './resty/jwt.so'
    no file '/usr/local/lib/lua/5.1/resty/jwt.so'
    no file '/usr/local/openresty/luajit/lib/lua/5.1/resty/jwt.so'
    no file '/usr/local/lib/lua/5.1/loadall.so'
    no file '/usr/local/openresty/site/lualib/resty.so'
    no file '/usr/local/openresty/lualib/resty.so'
    no file './resty.so'
    no file '/usr/local/lib/lua/5.1/resty.so'
    no file '/usr/local/openresty/luajit/lib/lua/5.1/resty.so'
    no file '/usr/local/lib/lua/5.1/loadall.so'
stack traceback:
coroutine 0:
    [C]: in function 'require'
    content_by_lua(nginx-listen-30086.conf:44):3: in main chunk, client: ::1, server:  _, request: "GET /sign HTTP/1.1", host: "localhost:30086"
::1 - - [01/Jun/2022:14:28:41 +0800] "GET /sign HTTP/1.1" 500 183 "-" "curl/7.64.1"

The key error message is:

/usr/local/openresty/nginx/sbin/nginx -c /Users/bswen/lua-projects/openresty-demo/conf/nginx.conf -g daemon off; pid '/Users/bswen/lua-projects/openresty-demo/nginx.pid';
2022/06/01 14:28:41 [error] 17956#0: *1 lua entry thread aborted: runtime error: content_by_lua(nginx-listen-30086.conf:44):3: module 'resty.jwt' not found:
    no field package.preload['resty.jwt']
    no file '/Users/bswen/lua-projects/openresty-demo/src/resty/jwt.lua'
    no file '/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/resty/jwt.lua'
    no file '/usr/local/openresty/site/lualib/resty/jwt.ljbc'

The code that cause the error is as follows:

nginx.conf:

    lua_package_path '/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/?.lua;;';

directory structure:

➜  resty git:(master) pwd
/Users/bswen/lua-projects/lua-resty-jwt/lib/resty
➜  resty git:(master) ll
total 112
-rw-r--r--  1 bswen  staff    11K Jun  1 14:24 evp.lua
-rw-r--r--  1 bswen  staff    15K Jun  1 14:24 jwt-validators.lua
-rw-r--r--  1 bswen  staff    27K Jun  1 14:24 jwt.lua
➜  resty git:(master)

lua code:

    location = /sign {
        content_by_lua '
                local cjson = require "cjson"
                local jwt = require "resty.jwt"

                local jwt_token = jwt:sign(
                    "lua-resty-jwt",
                    {
                        header={typ="JWT", alg="HS256"},
                        payload={foo="bar"}
                    }
                )
                ngx.say(jwt_token)
            ';
    }

2. Reason

Openresty try to find the lua library from the lua_package_path, if the lua_package_path is as follows:

lua_package_path '/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/?.lua;;';

if you import library as follows:

local jwt = require "resty.jwt"

openresty will try to find the library from this path:

/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/resty/jwt.lua

You can see that the above path does NOT match our directory structure. That is the problem.

What is lua_package_path?

syntax: lua_package_path

default: The content of LUA_PATH environment variable or Lua’s compiled-in defaults.

context: http

Sets the Lua module search path used by scripts specified by set_by_lua, content_by_lua and others. The path string is in standard Lua path form, and ;; can be used to stand for the original search paths.

 # Set the search path for pure Lua extension libraries (';;' is the default path):
 lua_package_path '/foo/bar/?.lua;/blah/?.lua;;';

 # Set the search path for Lua extension modules written in C (can also use ';;'):
 lua_package_cpath '/bar/baz/?.so;/blah/blah/?.so;;';

3. Solution

change nginx.conf’s lua_package_path from

    lua_package_path '/Users/bswen/lua-projects/lua-resty-jwt/lib/resty/?.lua;;';

to

    lua_package_path '/Users/bswen/lua-projects/lua-resty-jwt/lib/?.lua;;';

4. Summary

In this post, I demonstrated how to solve the module not found error when running a lua script in openresty, the key point is to set the correct lua_package_path that matches your directory structure . That’s it, thanks for your reading.