How to resolve "undefined symbol: lua_resty_ffi_init"

[vikirj]

I have installed lua-resty-ffi to enable HTTP/3 support by following these steps:

luarocks config variables.OR_SRC /tmp/tmp.Z2UhJbO1Si/openresty-1.21.4.1
luarocks install lua-resty-ffi

This successfully generated the libresty_ffi.so file at:

/usr/local/lib/lua/5.1/libresty_ffi.so

However, when sending a request, I encountered the following error in the logs:

2025/09/09 11:53:31 [info] 3054922#0: *19 client closed connection while waiting for request, client: 192.168.1.1, server: 0.0.0.0:443
2025/09/09 11:53:31 [debug] 3054918#0: *18 [lua] access_by_lua(nginx.conf:56):2: Route: /test_route Client IP: 192.168.1.1
2025/09/09 11:53:31 [info] 3054918#0: *18 [lua] test.lua:115: TestRoute(): 192.168.1.2:5000, client: 192.168.1.1, server: 127.0.0.1, request: "GET /test_route HTTP/1.1", host: "test.duckdns.org"
2025/09/09 11:53:31 [debug] 3054918#0: *18 [lua] test.lua:117: TestRoute(): Resolve request url: https://192.168.1.2:5000/test_route
2025/09/09 11:53:31 [error] 3054918#0: *18 lua entry thread aborted: runtime error: /usr/local/share/lua/5.1/resty_ffi.lua:110: /usr/local/lib/lua/5.1/libresty_ffi.so: undefined symbol: lua_resty_ffi_init
stack traceback:
coroutine 0:
	[C]: in function 'require'
	.../openresty/test.lua:125: in function 'TestRoute'
	access_by_lua(nginx.conf:56):3: in main chunk, client: 192.168.1.1, server: 127.0.0.1, request: "GET /test_route HTTP/1.1", host: "test.duckdns.org"

To debug this, I inspected the shared library with the command:

nm -D libresty_ffi.so
The output indicates that the lua_resty_ffi_init symbol is missing:

000000000000150e T build_id_data
00000000000013e9 T build_id_find_nhdr_by_name
000000000000145a T build_id_find_nhdr_by_symbol
00000000000014f9 T build_id_length
                 w __cxa_finalize@GLIBC_2.2.5
                 U dladdr@GLIBC_2.34
                 U dl_iterate_phdr@GLIBC_2.2.5
                 w __gmon_start__
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable
                 U memcmp@GLIBC_2.2.5
                 U __stack_chk_fail@GLIBC_2.4
                 U strcmp@GLIBC_2.2.5

As you can see, the function lua_resty_ffi_init is not defined in the shared object file.

How can I resolve the undefined symbol: lua_resty_ffi_init error and properly load libresty_ffi.so ? Anything I missed during installation?

[kingluo]

@vikirj you should compile openresty with --with-threads, because lua-resty-ffi depends on the nginx thread pool.