[ZODB-Dev] Shared/DC/ZRDB/TM.py:_register

[Vincent Pelletier]

Le Tuesday 13 May 2008 20:02:42 Dieter Maurer, vous avez écrit :
> Someone convinced us that error handling should (of course)
> see the state the error happened and not a new clean state -- in
> order to be able to report about the errorneous state....

Then, in my opinion, it should not be executed "inside" what failed, but in a 
clean environment with a "pointer" (in non-technical meaning) to the failed 
transaction.
Or there must be some special directives about what can or cannot happen in an 
error handler (but I guess it's just too hard to make sure nothing joins a 
transaction, for example fetching a page template from ZODB to render the 
error will join the transaction).

> Another reason was also: should your error template need to run
> in a fresh transaction, then just abort the old one.

How ? IIRC it's a bad coding practice to interact with transaction mechanism 
from what's considered as "inside" a transaction (ZPublisher being the 
borderline).

> If the transaction were aborted before error handling, then
> an error template with different requirements does not have a chance....

Right.

Maybe 2 cases should be handled differently:
 - exception happened when processing transaction: do not abort immediately
 - exception happened in transaction handling (hopefully only in "commit"):
   abort to offer error handling a "usable" environment

Anyway, I opened a bug in the bugtracker about this problem, because it's a 
separate issue from the TM.py problem:
  https://bugs.launchpad.net/bugs/229863

-- 
Vincent Pelletier