Of course its up to me to determine if it's a data collision or not, but I was thinking may be Twisted can provide me with some already existing mechanism of its own. After all its already a pretty massive and complicated framework with tons of capabilities ... But I'd like to get back to the point of the question: if at some point EventA callbacks and EventB callbacks need to work on the same global variable, than what would be a Twisted way (if exist) to prevent data collision ? Thank you. Quoting Nitro <nitro@dr-code.org>:
Am 28.05.2010, 20:34 Uhr, schrieb <vitaly@synapticvision.com>:
hi,
Callbacks serialization is clear to me.
I'll try to rephrase the question: two requests are incoming for reactor() to handle. Each request has its own chain of callbacks. At some point one of the requests need to update the same global data structure, and another request need to delete from the same global data structure. So theoretically, correct me if I wrong, will be a data collision. If it is, than how can I prevent it? Example please.
It will go like this:
reactor loop:
1) receive Event A - fire deferred callback - deferred callback does data[key] = value 2) receive Event B - fire deferred callback - del data[key]
So one event is processed after another. Determining if it's a data collision is up to you. E.g. you could use something like a revision number. Each time you change the dictionary, increase it by one. Then if you try to change the dictionary and the client gave a different revision id then the last one, you know there is a collision. What you do sounds very much like database transactions. Those are not easy to do. One example is the ZODB which can do what you want. For example via BTrees. But I guess there are more lightweight systems which do what you want, too. It all depends where you want to go with your app. That's up to you though and not really a question in regards to twisted or networking.
-Matthias
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