Supercharging NGINX with Lua (Part 2)

In Supercharging NGINX with Lua (Part 1) we demonstrated how to install NGINX with Lua support (via the OpenResty package). In this post I'll walk through some simple, but powerful examples of Lua integrations.

For the below examples I am assuming that you have installed NGINX capable of handling Lua scripts, and have a basic working NGINX configuration file (to embed the location blocks below in).

Important: Although the examples below will work, they are somewhat contrived (over-simplified) and are primarily intended for demonstration of Lua capabilities; if you decide to use the examples in your own environments, please make sure that you understand what they are doing and tailor them to your own requirements; Phew... legal stuff done!

Lastly, there is very comprehensive NGINX Lua Module Documentation and OpenResty Documentation in which the NGINX Lua commands and constructs are explained in detail; if you are unsure about a particular command or method I highly recommend starting there!

Example 1. Basic Lua handler (embedded)

Here we utilize Lua to respond with: "OK":

location /example1 {
  content_by_lua_block {
    ngx.say("OK")
  }
}

Example 2. Basic Lua handler (modular)

Here we again utilize Lua to respond with: "OK!", however we use a separate Lua file. This is recommended to allow you to separate your concerns.

Note: that with later versions of Lua NGINX you can also provide these files in pre-compiled Lua/LuaJIT bytecode (for faster start times).

To start we create file /etc/lua/example2.lua with content:

ngx.say("OK!")

Then include the following in our NGINX config:

location /example2 {
  content_by_lua_file /etc/lua/example2.lua;
}

Example 3. Lua for auth

Here we utilize Lua to authorize a request based on the remote_user, remote_address and URI. We create file /etc/lua/example3.lua with content:

local remote_user = ngx.var.remote_user
local remote_addr = ngx.var.remote_addr
local uri = ngx.var.uri

if string.match(remote_user, "frankie") and 
   string.match(remote_addr, "123.123.123.123") and 
   string.match(uri, "[%a%d_%-.]+") then
  -- we are ok here!
else
  ngx.exit(ngx.HTTP_FORBIDDEN)
end

Then include the following in our NGINX config:

location /example3 {
  access_by_lua_file /etc/lua/example3.lua;
}

Next Steps

Part 3 of this series will illustrate some more advanced examples of how we can now use Lua modules to do some ultra-cool stuff like request-caching and embedded http requests.