Is it possible to have live reloading of lua scripts using openresty and docker?

Question

I'm newish to LUA and want to practice some LUA scripting using nginx/openrestry.

Is there a workflow where I can use docker that runs openresty, and link my laptops filesystem to my docker container such that when I make a change to my lua script, I can quickly reload openrestry server so I can quickly see my lua changes take effect?

Any help or guidance would be appreciated.

Answer 1

You can disable Lua code cache — https://github.com/openresty/lua-nginx-module#lua_code_cache — add lua_code_cache off inside the http or server directive block. This is not actually “hot reload”, it's more like php request lifecycle:

every request served by ngx_lua will run in a separate Lua VM instance

You can think of it as if the code is hot–reloaded on each request.

However, pay attention to this:

Please note however, that Lua code written inlined within nginx.conf [...] will not be updated

It means that you should move all your Lua code from the nginx config to Lua modules and only require them:

server {

  lua_code_cache off;

  location /foo {
    content_by_lua_block {
      -- OK, the module will be imported (recompiled) on each request
      require('mymodule').do_foo()
    }
  }

  location /bar {
    content_by_lua_block {
      -- Bad, this inlined code won't be reloaded unless nginx is reloaded.
      -- Move this code to a function inside a Lua module
      -- (e.g., `mymodule.lua`).
      local method = ngx.req.get_method()
      if method == 'GET' then
        -- handle GET
      elseif method == 'POST' then
        -- handle POST
      else
        return ngx.exit(ngx.HTTP_NOT_ALLOWED)
      end
    }
  }

}

Then you can mount your Lua code from the host to the container using --mount or --volume: https://docs.docker.com/storage/bind-mounts/