[Python-Dev] Re: PEP 282 comments (original) (raw)

Jeremy Hylton jeremy@zope.com
Wed, 20 Mar 2002 18:08:27 -0500

On Wed, 20 Mar 2002 22:57:44 -0000 "Vinay Sajip" <vinay_sajip@red-dove.com> wrote:

I have to declare a preference for Mark's and Guido's approach. The reason is - what is a "normal" exception? And if it is "normal", why do we need to see a stack trace for it?

ZEO is a component that lets clients on remote machines access a ZODB storage using a custon Python RMI. (The details aren't exactly important, except that it's a concrete example.) IOW, ZEO + ZODB is a client-server object database.

It's possible for all sorts of things to go wrong for an individual RMI. There can be a problem marshalling or unmarshalling the objects. There can be a problem with executing the actual methods on the server. There can be a problem with application code that is executed as a result of calling some method on the server. Etc.

Few of these errors are fatal. Some of them may be uninteresting most of the time. So I'd like to log tracebacks and vary the log level depending on the importance of the event that caused the exception.

One particular example is a KeyError. The server will raise a KeyError if the client asks for an object that doesn't exist. There are clients that catch this error on the client side and handle it cleanly. It's not an important exception for them. But I'd like to log the traceback on the server to handle cases where the client isn't expecting it. I'd probably log this at debug() level. Most of the time, nobody cares about a KeyError. But it might occasionally be useful when debugging something.

Jeremy