I don’t know how to iterate “query.request.qsource.headers”.

These C structures have nice Lua bindings.  I believe you can just for-loop from headers.at[0] up to headers.at[headers.len - 1]

Generally, in almost all cases we use just this auto-mapping between C and Lua: https://luajit.org/ext_ffi_tutorial.html#idioms

(I don't recall if all http headers get always pulled into this structure, but you should see that practically soon.)

--Vladimir