6 ms·

Could someone explain to me why would I choose this over https://github.com/openresty/lua-nginx-module https://github.com/openresty/lua-nginx-module ? It suppor

by chx 8y ago

Could someone explain to me why would I choose this over https://github.com/openresty/lua-nginx-module https://github.com/openresty/lua-nginx-module ? It supports LuaJIT and while I suppose it is possible to write faster C code by hand than JIT translated Lua it'd be hard and I'd fear the maintainability of hand optimized C code.

kbenson 8y ago
It might be easier to tie in a few different external libraries if you're using C than with Lua FFI, depending on the libraries.
legohead 8y ago
It's faster like you said. but probably the main benefit are people who have already developed a large program in C. C isn't hard to maintain -- it's not some mystical language..
- Something1234 8y ago
  It just takes discipline. The discipline to not haphazardly throw macros all over the place, and keep them pure(no side effects).
  - abstractbeliefs 8y ago
    Sadly, the reason that discipline is such a vaunted virtue is because it's hard. Even the most well meaning and diligent C developers still make mistakes. Tools should be ergonomic, they should reduce the need for diligence, care, discipline, and intelligence. I'm not saying that the above aren't all important to programming, or that we should abandon anything that's not easy, but we're humans and make human mistakes and tools that are unforgiving when we do are ripe to be replaced by those that nudge us back on track.
    - Something1234 8y ago
      Mostly the compiler just needs to slap your hand harder, and tell you no when you do something stupid or depend on undefined behavior. Also better static analysis would be nice. I completely agree with you on all points. Languages exist to make our lives easier.
      - abstractbeliefs 8y ago
        Well, there's a little more than that, as we actually have told compiler devs we don't want that. When developers demand that compilers compete with each other on fractions of a percent of runtime performance, we set ourselves up for things like UB acting in unintuitive ways. When people give us the choice between safer but slower systems, and fast but unsafe ones, until recently people have overwhelmingly chosen fast and unsafe and pretended they're superhuman enough to not write bad code.
      - anonymoushn 8y ago
        This is probably too much to ask for. I recently fixed an issue caused by UB in openresty of the form "nginx uses a NULL pointer and a length of 0 to signify a null string" + "nginx sometimes searches for strings in other strings using a function that takes start and end pointers for the haystack". This function works fine on lots of 0-length haystack strings (probably returning no match), but as you probably know, NULL + 0 is allowed to evaluate to anything. This seems pretty hard to detect statically short of banning programs that do arithmetic on any pointer without first NULL checking it.
    - sureaboutthis 8y ago
      That's why we choose to use C and do the other things, not because it is easy, but because it is hard, because that goal will serve to organize and measure the best of our energies and skills.
comex 8y ago
For one thing, you don't have to use this module with C. Any language that supports exporting C-compatible functions will do – there's C++ of course, but also Rust, Go, D, Nim, and many many others.
- shakna 8y ago
  LuaJIT also supports C-functions. It's FFI [0] will allow you to declare any C-compatible function or data structure, and then use it in normal Lua code. [0] https://luajit.org/ext_ffi.html https://luajit.org/ext_ffi.html
  - guipsp 8y ago
    Why would you ever opt to go thru Lua in this case?
    - shakna 8y ago
      It's well supported, well maintained, and around for the foreseeable future. (OpenResty) The language implementation is fast, and allows you to tap into any C-compatible library. The question isn't why you would go through Lua, but why you would choose something with less support?
  - Hello71 8y ago
    This doesn't seem to support actually exporting C-compatible functions.
    - shakna 8y ago
      Create some Lua code that runs within C? Rather than just passing and converting to C values when needed? That's the role of the C API [0]. But usually you'd just be passing C up to Lua to bind it together. [0] https://luajit.org/ext_c_api.html https://luajit.org/ext_c_api.html
      - annchin_peh 8y ago
ksec 8y ago
Or something "lighter" like H20 with mRuby? https://h2o.examp1e.net/index.html https://h2o.examp1e.net/index.html
annchin_peh 8y ago
Hmm.. I've tried luaJit module and I've given up half way when building as it seemed a lot of compatibility issue(maybe not professional enough to build), sincerely I don't know lua and I prefer go for c module over any other language mixed together since nginx is build from C For nginx-c-function, it's easy build and I can build this as dynamic module and use it with other servers which has same version of nginx. It might be good to use lua if the person not good in c/c++.

by chx 8y ago

kbenson 8y ago

It might be easier to tie in a few different external libraries if you're using C than with Lua FFI, depending on the libraries.

legohead 8y ago

It's faster like you said. but probably the main benefit are people who have already developed a large program in C. C isn't hard to maintain -- it's not some mystical language..

Something1234 8y ago
It just takes discipline. The discipline to not haphazardly throw macros all over the place, and keep them pure(no side effects).
- abstractbeliefs 8y ago
  Sadly, the reason that discipline is such a vaunted virtue is because it's hard. Even the most well meaning and diligent C developers still make mistakes. Tools should be ergonomic, they should reduce the need for diligence, care, discipline, and intelligence. I'm not saying that the above aren't all important to programming, or that we should abandon anything that's not easy, but we're humans and make human mistakes and tools that are unforgiving when we do are ripe to be replaced by those that nudge us back on track.
  - Something1234 8y ago
    Mostly the compiler just needs to slap your hand harder, and tell you no when you do something stupid or depend on undefined behavior. Also better static analysis would be nice. I completely agree with you on all points. Languages exist to make our lives easier.
    - abstractbeliefs 8y ago
      Well, there's a little more than that, as we actually have told compiler devs we don't want that. When developers demand that compilers compete with each other on fractions of a percent of runtime performance, we set ourselves up for things like UB acting in unintuitive ways. When people give us the choice between safer but slower systems, and fast but unsafe ones, until recently people have overwhelmingly chosen fast and unsafe and pretended they're superhuman enough to not write bad code.
    - anonymoushn 8y ago
      This is probably too much to ask for. I recently fixed an issue caused by UB in openresty of the form "nginx uses a NULL pointer and a length of 0 to signify a null string" + "nginx sometimes searches for strings in other strings using a function that takes start and end pointers for the haystack". This function works fine on lots of 0-length haystack strings (probably returning no match), but as you probably know, NULL + 0 is allowed to evaluate to anything. This seems pretty hard to detect statically short of banning programs that do arithmetic on any pointer without first NULL checking it.
  - sureaboutthis 8y ago
    That's why we choose to use C and do the other things, not because it is easy, but because it is hard, because that goal will serve to organize and measure the best of our energies and skills.

comex 8y ago

For one thing, you don't have to use this module with C. Any language that supports exporting C-compatible functions will do – there's C++ of course, but also Rust, Go, D, Nim, and many many others.

shakna 8y ago
LuaJIT also supports C-functions. It's FFI [0] will allow you to declare any C-compatible function or data structure, and then use it in normal Lua code. [0] https://luajit.org/ext_ffi.html https://luajit.org/ext_ffi.html
- guipsp 8y ago
  Why would you ever opt to go thru Lua in this case?
  - shakna 8y ago
    It's well supported, well maintained, and around for the foreseeable future. (OpenResty) The language implementation is fast, and allows you to tap into any C-compatible library. The question isn't why you would go through Lua, but why you would choose something with less support?
- Hello71 8y ago
  This doesn't seem to support actually exporting C-compatible functions.
  - shakna 8y ago
    Create some Lua code that runs within C? Rather than just passing and converting to C values when needed? That's the role of the C API [0]. But usually you'd just be passing C up to Lua to bind it together. [0] https://luajit.org/ext_c_api.html https://luajit.org/ext_c_api.html
    - annchin_peh 8y ago

ksec 8y ago

Or something "lighter" like H20 with mRuby? https://h2o.examp1e.net/index.html https://h2o.examp1e.net/index.html

annchin_peh 8y ago

Hmm.. I've tried luaJit module and I've given up half way when building as it seemed a lot of compatibility issue(maybe not professional enough to build), sincerely I don't know lua and I prefer go for c module over any other language mixed together since nginx is build from C For nginx-c-function, it's easy build and I can build this as dynamic module and use it with other servers which has same version of nginx. It might be good to use lua if the person not good in c/c++.