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#53 Report original exception for session unpickle error
The purpose of this patch is to provide the original
session unpickle exception instead of KeyError
exception.
---
Since we have no corrupted sessions on the disk, the
Session KeyError is still appears.
KeyError appears if SessionFileStore can't unpickle
session while loading it from disk.
Session can't be unpickled only if it has objects, with
have buggy implemented unpickling feature.
Developer, who works under webkit, would like to fix
unpickling for his session.
So, match better for developer to see the original
exception instead of KeyError.
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This patch was made on Webware0.8b1.
The patch
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Wouldn't this part of the patch be easier if we just said
"raise"? raise with no arguments re-raises the latest
exception. There's no need to rebuild it from sys.exc_info().
+ e = sys.exc_info()
+ raise e[0], e[1], e[2] # raise the exception again, so
developers can look on it
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I'm not sure it's a good idea to re-raise the unpickling
exception here. It may be better to _print_ the unpickling
exception and possibly email it to the administrator, but
still raise KeyError so that the application can treat this
as a missing session and possibly recover more gracefully.
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Here is KeyError traceback:
Traceback (most recent call last):
File ".\WebKit\Application.py", line 368, in dispatchRequest
elif self.isSessionIdProblematic(request):
File ".\WebKit\Application.py", line 466, in
isSessionIdProblematic
if (time()-request.session().lastAccessTime()) >=
request.session().timeout():
File ".\WebKit\HTTPRequest.py", line 225, in session
return self._transaction.session()
File ".\WebKit\Transaction.py", line 67, in session
self._session =
self._application.createSessionForTransaction(self)
File ".\WebKit\Application.py", line 889, in
createSessionForTransaction
session = self.session(sessId)
File ".\WebKit\Application.py", line 725, in session
return self._sessions[sessionId]
File ".\WebKit\SessionDynamicStore.py", line 72, in
__getitem__
self.MovetoMemory(key)
File ".\WebKit\SessionDynamicStore.py", line 135, in
MovetoMemory
self._memoryStore[key] = self._fileStore[key]
File ".\WebKit\SessionFileStore.py", line 55, in __getitem__
raise KeyError, key
KeyError: 20030204232946-
b46a22352890568b1a899c361d816933
Seems that KeyError have thrown out of awake-respond-sleep
cycle (before it), so servlet can’t perform any gracefull
recoveries. Maybe application must recover the same way as
when session can’t be pickled? To remove unpickable
session file, to create new session, and not to throw any
exception at all?
Any way, it usefull to see original exception report – in
console/log, or in http exception report.
---
I have raised exception like “raise e[0], e[1], e[2]” just to
preserve original traceback. If original traceback has no
helpful information, we can simple &#8220;raise <original exception
instance>&#8221;
The simplest patch is to remove try/except at all :)
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The original traceback is preserved if you just do "raise"
without any arguments. It just re-raises the existing
exception along with existing traceback information.
From a consistency point of view, raising a KeyError for
problems retrieving a session seems to be pretty common.
While I think this specific case is not caught, there are
other cases where a session stores __getitem__ throws a
KeyError that does get caught.
From a users point of view, shouldn't this just appear as a
missing session file?
From a developers view, you would want to see what the
unpickling error was.
If these two assumptions are correct, then perhaps a
solution like this:
- catch KeyError in Application.createSessionForTransaction,
and treat it like there was no session.
- have the decoding exception raise a key error as it does
now, but also print out a the stack trace for a developer,
possibly calling handleException() to log the exceptino as well.
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So I've produced patches:
for Application: Application.diff
for SessionfileStore.diff
in SessionFileStore.__getitem__:
* close session file finally (seems like bug fix)
in case of session unpicling error:
1. remove session file
2. call Application.handleException()
3. raise KeyError
in Application.createSessionForTransaction:
1. catch KeyError
2. create new session if it was not loaded from store
in replace of SessionFileStore2.diff
in addition to SessionFileStore.diff
new patch works within isSessionIdProblematic()
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Check out the revised Application2.diff I am uploading.
This places the catch of the KeyError in
isSessionIdProblematic() which is called specifically to see
if a session ID is valid when processing dispatchRequest().
If it fails (typically because the sesion has expired) it
marks the session as expired so the servlet can check and
handle the situation.
It has the advantage of cleaning up _SID_ cookies and fields
on the request and going through handleInvalidSession which
honors the setting 'IgnoreInvalidSession'
Please advise if this solves your problem. Note it should
be used in addition to the SessionFileStore.diff patch which
raises the KeyError.
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Aplication2.diff in couple with SessionFileStore.diff seems
works fine.
Request reports like session expired if session had unpickle
problems. And we haveoriginal traceback in console.
Thanks.
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Committed fix to CVS.