Re: Lua and multi-threaded FastCGI servers

[Wim Couwenberg <wcou@...>]

> - Is LuaThreads a separate package or is it the coroutines facility 
> within standard
> Lua for doing non-pre-emptive threading in a Lua script? Does it sit on top
> of Posix threads (saw references to LuaThreads on top of eCos threads
> elsewhere)?

I'm not knowledgable on LuaThreads (I'm sure Diego will answer your 
question).  However, from my own experience and what I read on this 
list, it is probably not a good idea to run several pre-emptive threads 
on one and the same Lua state.  The locking overhead can be quite high. 
 I'd stick with a Lua state per thread and handle marshalling of any 
data yourself.

> - I can see a lua_newthread() API that can be called from C - is this an
> alternative to creating my own Posix thread and then lua_open()'ing a new
> Lua VM within that thread (which was what I was trying to do now)?

No.  lua_newthread is for coroutine support.  It creates a "Lua thread" 
(essentially a separate call stack) as a data structure in a Lua state. 
 It does not offer or support pre-emptive threading automatically (i.e. 
you still need some extension).  There are endless discussions about 
coroutines on this list and they are explained in the manual and in PIL.

> - lua_set/gettable(L, LUA_GLOBALSINDEX) vs. lua_set/getglobal(L, 
> "global_id")
> as a way of setting/getting globals in a Lua VM. Are these equivalent or
> have I confused two concepts?

Equivalent.  The _global versions save you an additional push call.

> - Also, lua_pcall vs. lua_cpcall. lua_cpcall seems to be the preferred 
> method
> for invoking a Lua script and not having the calling program terminate 
> if an
> error occurs since the C function passed to lua_cpcall will return to the
> function calling lua_cpcall in the event of an error?

Depends on your situation.  To safely call a function on the Lua stack 
lua_pcall is just what you'll need.

--
Wim