How to Configure a Virtual Domain and Run Lua Scripts with OpenResty

Overview

To simplify development, a virtual domain http://openresty.tinywan.com is configured locally. Create a configuration file openresty.tinywan.com.conf under /usr/local/openresty/nginx/conf with the following minimal server block:

server {
    listen 80;
    server_name  openresty.tinywan.com;
}

Write location Block

Add a location /lua block to the server configuration to return a simple "Hello World" message using Lua:

location /lua {
    default_type 'text/html';
    content_by_lua 'ngx.say("Hello World")';
}

Validate the Nginx configuration syntax: /usr/local/openresty/nginx/sbin/nginx -t If the syntax is OK, reload the service: sudo systemctl restart openresty.service or /usr/local/openresty/nginx/sbin/nginx -s reload Visiting http://openresty.tinywan.com/lua should display Hello World.

Use External Lua Script Files

Embedding Lua code directly in the configuration can become unwieldy. Create a lua directory under /usr/local/openresty/nginx/conf and add hello.lua with the content:

ngx.say("Hello 开源技术小栈")

Update the server block to load the script file:

server {
    listen 80;
    server_name  openresty.tinywan.com;

    location /lua {
        default_type 'text/html';
        content_by_lua_file conf/lua/hello.lua; # relative to the nginx installation directory
    }
}

The script path can also be absolute, e.g., /usr/local/openresty/nginx/conf/lua/hello.lua. After restarting OpenResty, test with:

curl -i http://openresty.tinywan.com/lua

lua_code_cache Setting

By default, lua_code_cache is enabled, caching compiled Lua code. Changes to Lua scripts require a full Nginx reload to take effect. During development you can disable the cache with lua_code_cache off; so that modifications are reflected immediately without reloading, but remember to enable it in production for performance.

server {
    listen 80;
    server_name  openresty.tinywan.com;

    location /lua {
        default_type 'text/html';
        lua_code_cache off;
        content_by_lua_file conf/lua/hello.lua;
    }
}

When the cache is turned off, reloading Nginx produces a warning:

nginx: [alert] lua_code_cache is off; this will hurt performance in /etc/nginx/conf.d/openresty.tinywan.com.conf:7

Error Logs

If runtime errors occur, check the error log:

tail -f /usr/local/openresty/nginx/logs/error.log

Sample error output showing an invalid return code in a configuration file:

2024/07/13 13:13:48 [emerg] 1#1: invalid return code "Hello World!" in /etc/nginx/conf.d/tinywan_lua.conf:7
2024/07/13 13:14:01 [emerg] 1#1: invalid return code "Hello World!" in /etc/nginx/conf.d/tinywan_lua.conf:7
2024/07/13 13:14:28 [emerg] 1#1: invalid return code "Hello World!" in /etc/nginx/conf.d/tinywan_lua.conf:7