Re: ACIDity of Prevayler 2.6

On Nov 15, 2012, at 5:00 AM, Klaus Wuestefeld wrote:

> > You would need teams that reliably produce perfect-zero
> > (not near zero :-) bugs for that to be practical.
> > To have a system that is so sensitive to unexpected problems
> > that all you can do is shut it down and fix the problem is unacceptable.
> 
> That seems exagerated to me. What about the other bugs that don't throw Exceptions? Since we can't be 100% let's just give up on writing software?

Klaus, you haven't answered my question. As far as I can see, without something to maintain consistency in the face of an unexpected exceptions, once that happens, the system is inconsistent and cannot proceed *for all users*. You must either a) shut down and fix the bug or b) remove the txn from the journal.

So unlike an ordinary db, which would isolate the exception to a single user, and let others continue to use the non-problemmatic parts of the system, an exception kills the whole thing. That's unacceptable to me.

If my reasoning is incorrect, or I'm missing something, and that is not true, I'd love to be refuted. We are building a system using prevayler, and really love it - but we've had to build a rollback mechanism (which we do by collecting inverses of any state change, and applying them on an exception) to deal with the above.

I'm also curious about why you are opposed to this? It seems the prevayler team has already implemented a scheme to handle it (the food taster) but took it out not because it was conceptually wrong, but because it was inefficent. Seriously - I'm very curious as to the history of that, as it seems it could throw some light on all this.

And in answer to your question - no, we shouldn't stop writing software, but some things are more problematic than others, and need a response.

Enjoy your camping! :-)

Best regards,

-pb

> 
> Klaus
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-pb

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