Duplicate Function Name in Different Modules

alexl · 2017-01-02T00:01:51+00:00

Thanks for the guidance, that’s very helpful. And on a slightly tangential topic, thanks much for your openresty...

Duplicate Function Name in Different Modules

alexl

Hello,

I have a few sites' configurations that make use of my custom "myModule.lua" module. I call require("myModule") and then able to use a function from there, called "replaceResource()".

So then from inside the *.conf file, inside "body_filter_by_lua" I make use of the said function.

I use require, because I read it only reads the module from the disk once and then just references it upon following requires.

I now added a new experimental configuration and added "myTestModule.lua" module, which I "require" from the body_filter_by_lua instead of myModule.

myTestModule Has the same function, but a different version of it.

I have noticed that after a number of iteration the new experimental configuration starts to encounter errors as it tries instead of intended "myTestModule" it uses "myModule"'s version of the function.

I solved this particular issue by just renaming the experimental function, BUT I am now in doubts that I may be doing something wrong?

What is the appropriate and efficient way of loading modules to avoid encountering same problems in the future?

An example from my *.conf:

location /
{
proxy_pass http://upstream_stream;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $host;
more_clear_input_headers Accept-Encoding;
default_type text/plain;
header_filter_by_lua 'ngx.header.content_length = nil';
body_filter_by_lua '
require "myTestModule"
responseBody = replaceResource(HTML)
ngx.arg[1] = responseBody
';
}

So "replaceResource()" should come from the "myTestModule.lua", but it uses one from the "myModule.lua".

Sorry for the long and kind of a theoretical question.

rpaprocki

Hi,

On Sun, Jan 1, 2017 at 8:01 AM, <al...@chameleonx.com> wrote:

Hello,
I have a few sites' configurations that make use of my custom "myModule.lua" module. I call require("myModule") and then able to use a function from there, called "replaceResource()".
So then from inside the *.conf file, inside "body_filter_by_lua" I make use of the said function.

I use require, because I read it only reads the module from the disk once and then just references it upon following requires.

I now added a new experimental configuration and added "myTestModule.lua" module, which I "require" from the body_filter_by_lua instead of myModule.
myTestModule Has the same function, but a different version of it.
I have noticed that after a number of iteration the new experimental configuration starts to encounter errors as it tries instead of intended "myTestModule" it uses "myModule"'s version of the function.
I solved this particular issue by just renaming the experimental function, BUT I am now in doubts that I may be doing something wrong?

What is the appropriate and efficient way of loading modules to avoid encountering same problems in the future?

An example from my *.conf:
location /
{
proxy_pass http://upstream_stream;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $host;
more_clear_input_headers Accept-Encoding;
default_type text/plain;
header_filter_by_lua 'ngx.header.content_length = nil';
body_filter_by_lua '
require "myTestModule"
responseBody = replaceResource(HTML)
ngx.arg[1] = responseBody
';
}

So "replaceResource()" should come from the "myTestModule.lua", but it uses one from the "myModule.lua".

Sorry for the long and kind of a theoretical question.

Have a look at https://github.com/openresty/lua-nginx-module#lua-variable-scope

In essence, using the style 'require "foo"' to add a function to the global namespace is bad form in this environment. The sanest way to load and use your module's function would be:

> location / {

> body_filter_by_lua_block {

> local mymodule = require "mymodule"

> local responseBody = mymodule.replaceResource(HTML)

> ngx.arg[1] = responseBody

> }

This creates a local copy of the mymodule require, and calls the replaceResource() functions as a member of that module. Your module would then look something like:

> local _M = {}
>
> _M.replaceResource(HTML)

> ...

> end

> return _M

And in this way, as each function is treated as a unique member of its module, there are no namespace collisions. Hope this helps!