On Jul 29, 2011, at 4:38 AM, Erik Allik wrote: > Thanks for another clear answer! I'll simply ignore zc.twist (for now > at least) and set up a classic thread pool. > I'll still probably use zc.twist's source as an example of how to > write transaction retrial on ConflicErrors and ClientDisconnecteds as > I haven't found anything similar elsewhere.
Cool. FWIW, http://pypi.python.org/pypi/zc.queue does something similar without threads. I prefer it (despite the fact that I said that "this testing approach has known weaknesses") if your use cases allow it. Gary > > Erik > > > > 2011/7/29 Gary Poster <gary.pos...@gmail.com>: >> >> On Jul 28, 2011, at 6:38 PM, Erik Allik wrote: >> >>> Gary, since you're the author of zc.twist (as I understand), I take >>> this as an exhaustive answer, and thank you :) >>> >>> However, I'm still curious to know zc.twist would provide any benefit >>> when used together with a thread pool. >>> The thread examples in its README (which I find hard to understand) >>> indicate that there must be some meaning to using zc.twist with >>> threads. >> >> The threads in the README are there to let me explore a running reactor >> within the doctest. They are not anything to emulate. >> >> The README overstates zc.twist's usefulness. As you point out, it blocks. >> If you assume that the ZODB is functioning normally, it won't block "much" >> but with standard definitions of blocking, it fails. For zc.async, that's >> fine--but a "while True" loop and a time.sleep() to give some breathing room >> probably would have been fine, with hindsight, and much simpler. The use of >> Twisted is a very questionable convenience, and the way zc.async uses >> Twisted is not to be copied 99% or more of the time. >> >> Gary >> >> >>> >>> Thanks again and best regards, >>> Erik >>> >>> >>> >>> 2011/7/29 Gary Poster <gary.pos...@gmail.com>: >>>> 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). >>>>> _______________________________________________ >>>>> For more information about ZODB, see the ZODB Wiki: >>>>> http://www.zope.org/Wikis/ZODB/ >>>>> >>>>> ZODB-Dev mailing list - ZODB-Dev@zope.org >>>>> https://mail.zope.org/mailman/listinfo/zodb-dev >>>> >>>> >> >> _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
