[Twisted-Python] win32 reactors

[James Mansion]

glyph at divmod.com wrote:
> On 01:39 pm, itamar at itamarst.org wrote:
>>
>> On Fri, 2008-03-28 at 06:23 +0000, James Mansion wrote:
>>> Shouldn't broken Win32 implementations be 'retired'?
>
> These implementations aren't "broken", so much as "limited".
>
Well, if they don't honour what the documentation says, then they seem 
broken
to me, and the documentation doesn't say you might get an unexpected
64 connection limit. No matter.
> Please feel free to contribute patches which reduce these limitations.
>> The old I/O Completion Ports reactor (which should be most scalable
>> Win32 reactor) was somewhat buggy. Twisted 8.0, released this week, has
>> a complete rewrite that hopefully is a lot better.
>
> It still doesn't support SSL, though:
>
>    http://twistedmatrix.com/trac/ticket/593
>
Need something patterned very much like Len's stuff
here http://www.lenholgate.com/archives/000456.html I guess.
> and maybe some other features too (I don't have a Windows handy or the 
> time required to read the code to check - this really ought to be 
> better-documented).
>
> The select reactor is also convenient for testing on Windows, because 
> it's the basis of at least one GUI reactor (GTK+) which should also 
> support Win32.
>
> Your suggestion for handle buckets in the win32eventreactor is one 
> which has been suggested before and sounds good to me.  Nobody has 
> bothered to implement it yet :).  However, even in its absence, I 
> don't believe we'll be completely dropping win32eventreactor because 
> it is useful for integrating with programs that do win32 drawing, even 
> if iocpreactor has higher performance and is more scalable.
Well, you need a daemon worker thread to call GetQueuedCompletionStatus(Ex)
and enqueue the results to the main thread, but that daemon worker doesn't
even need to have the full support of the C library multithreading so 
long as it just
swizzles pointers and calls raw API routines. Its normally more of a 
gotcha that
you might try to submit IO from a pool thread that might reasonably be 
terminated
before the IO completes. Why do you need an event reactor to support win32
applications, except to call MsgWait... rather than 
GetQueuedCompletionStatus?

On a similar sort of topic - is there a reason to have lots of 
implementations
for POSIX, rather than use libevent or libev?

James