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

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/