[ZODB-Dev] Twisted, ZODB and zc.twist

[Gary Poster]

Hello Erik.  As the author, I'll suggest that you move on to a ZODB connection pool used by the usual Twisted-provided thread pool.  zc.twist is maybe interesting and maybe clever, but of very limited usefulness.  I suspect it is only used in zc.async, and that's probably as it should be.  It's a case of premature generalization.

If you are going to use Twisted in anything like a normal way, and the ZODB in anything like a normal way, use a connection pool and threads.

Best,

Gary


On Jul 28, 2011, at 4:12 PM, Erik Allik wrote:

> Hello everyone,
> 
> I hope this is the right mailing list to post this question to.
> 
> I'm trying to build an Twisted application that uses ZODB and I've
> also found zc.twist.
> I've read its README as well as the source code to try to understand
> how exactly and why I should use zc.twist, and also asked the same
> questions on irc.freenode.net #zope but without a conclusive answer.
> 
> What I'm not able to understand is whether using zc.twist will allow
> me to do all ZODB access in the main Twisted thread, or if still need
> to set up a thread pool and deferToThread any code that accesses the
> DB.
> 
> The README of zc.twist has:
> "Everything can be done within the main thread, so it can be full-bore
> Twisted usage, without threads."
> 
> However, looking at the source code of zc.twist, I cannot find any
> reference to async communication (callbacks/polling) with ZODB, so
> it's difficult to conclude that all DB access is non-blocking and can
> be done in a single thread. Also, there are some examples with threads
> in the README.
> 
> I would highly appreciate if somebody with a clearer understanding of
> this could explain to me whether I in fact need to set up a thread
> pool, and in any case, what exactly is zc.twist for regardless of
> whether it needs to be used with a threadpool or not.
> 
> Thanks in advance!
> 
> Regards,
> Erik Allik
> 
> P.S. I'd be very thankful for any references to open source
> projects/code using ZODB with Twisted, or even zc.twist (besides
> zc.async).
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