feat(build): build wasmx as static or dynamic module

[locao]

Summary

This change makes it possible to build ngx_wasm_module as a dynamic Nginx module.

It adds the new flag --//:wasmx_module, which accepts dynamic and static options. Currently dynamic is the default value.

There is a new feature to include the load_module directive in nginx.conf when dynamic module is in use and wasm = on. It will search for the shared object in the path defined by the environment variable KONG_DYNAMIC_MODULES_PATH, the nginx build prefix and then in /usr/local/openresty/nginx/modules (the default installation path).

Checklist

• The Pull Request has tests
• There's an entry in the CHANGELOG
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Full changelog

• Build scripts changed.

Issue reference

KAG-664

[flrgh]

What's stopping us from just adding this to the template?

[...]

error_log ${{PROXY_ERROR_LOG}} ${{LOG_LEVEL}};

> if wasm then
load_module /path/to/ngx_wasm_module.so;
> end

[...]

[locao]

If the module is built statically, ngx_wasm_module.so will not exist and the config check will fail. We can remove the line in this case instead of adding, but it seems the build script complexity would be similar.

[flrgh]

Hmm. I bet there's a way to detect this in the conf loader.

We could parse ngx.config.nginx_configure to check for --add-module vs --add-dynamic-module and choose whether or not to add load_module. This would even help to provide nicer errors before doing a conf test (i.e. if the user turns wasm on, but we can't find ngx_wasm_module in the configure string, raise an error).

Either that or maybe we copy the dynamic module to some known path, and the conf loader can check for the existence of /path/to/dynamic/ngx_wasm_module.so in order to determine adding load_module.

Does that sound like it work, or am I not understanding things fully?

[locao]

That's a nice idea! I made the needed changes, wdyt?

Now the module is looked up in 3 different locations, in order: KONG_DYNAMIC_MODULES_PATH env var, the build prefix path and then /usr/local/openresty/nginx/modules. The second one is needed for the dev env but will not work in the production env. I think it's a acceptable performance penalty as this function is called only when starting.