[ZODB-Dev] Possible ZEO bug: DSToolkit permanently disconnects after ZEO restart

[Paul Winkler]

Hi,

I brought this up a while ago on dirstorage-users.
Toby Dickenson suggested it might possibly be a ZEO bug.

The issue, with detailed repro instructions:
http://sourceforge.net/tracker/index.php?func=detail&aid=1106702&group_id=53818&atid=471702

Toby's response from dirstorage-users:
http://sourceforge.net/mailarchive/message.php?msg_id=10470537

Summary:

- if ZEO ever restarts, the DSToolkit Product can no longer do its job
  (forcing the storage into Snapshot mode) - instead ZEO raises
  DisconnectedError, even though all other Zope activity proceeds
  as normal, i.e. Zope is NOT disconnected from ZEO.
  Restarting Zope makes the symptom go away.

- I can reproduce this on Zope 2.7.3

- Toby can NOT reproduce this with Zope 2.6.x

- Toby says "DirectoryStorage is using ZEO's getExtensionMethods API,
  and I supect the problem will be there."

Now, I don't know squat about getExtensionMethods except what
I've learned browsing the ZEO source in the past few minutes.
But here's what I see:

>From a brief look, DSToolkit is a very simple Product. 
It contains a couple of methods that in turn invoke ZEO extension methods. 
Here's an example:

    security.declareProtected('Manage DirectoryStorages','is_directorystorage')
    def is_directorystorage(self):
        if self._v_is_directory_storage is None:
            storage = self._p_jar._storage
            try:
                fn = storage.is_directory_storage
            except AttributeError:
                self._v_is_directory_storage = 0
            else:
                self._v_is_directory_storage = fn()
        return self._v_is_directory_storage


... which method of the storage is referred to in
BaseDirectoryStorage.py:

    def getExtensionMethods(self):
        return {'enter_snapshot': None,
                'leave_snapshot': None,
                'get_snapshot_code': None,
                'is_directory_storage': None,
                }

... which looks fine according to the API in ClientStorage.py;
a bit further down in BaseDirectoryStorage.py 
is the method definition:

    def is_directory_storage(self):
        return 1



So, everything in DirectoryStorage and DSToolkit looks kosher to me;
is this a ZEO bug? 

If so, I'll file a collector issue (but where? in the Zope collector?)

thanks,

-- 

Paul Winkler
http://www.slinkp.com