Shane Hathaway wrote:
Jeremy Hylton wrote:

On Tue, 2003-02-11 at 12:10, Shane Hathaway wrote:

I added a test to on a new branch (shane-conflict-handling-branch) that exercises the conflict handling bug. The test currently fails. It might be simpler to go with Toby's implementation for now: add a "veto" object to the transaction that refuses any attempt to commit. But maybe your transaction states are better. Let me know what you want to do.

I'd like to do the transaction states, because it would keep the code in
zodb3 and zodb4 similar.  Unless there's a reason to think there are
problems with the transaction state approach.

That would be fine. We only need all tests (including the new test) to pass. :-)

I didn't look carefully at the test, but if I remember the discussion
last time around, the problem is with read conflicts caught outside of
2PC.  In that case, we either need to mark the connection so that it
votes no when it gets to prepare() or we need to veto() method.  I'd
prefer the vote-no-in-prepare because it keeps the API smaller, but
veto() isn't so bad; maybe it's better to stop the transaction quickly.

If we have veto(), it should probably expect a string argument that explains the reason for the veto. Then if something tries to commit, we can raise VetoedError(explanation). Otherwise, it seems like failed transactions would be opaque and hard to decipher.
hm this is starting to look an awful lot like Persistent Java Beans.
maybe you should take a look there and borrow some architecture.


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