[ZCM] [ZC] 1724/ 1 Request "ZEO "extension methods" fail after ZEO restarts?"

[Collector: Zope Bugs, Features, and Patches ...]

Issue #1724 Update (Request) "ZEO "extension methods" fail after ZEO restarts?"
 Status Pending, Database/bug medium
To followup, visit:
  http://www.zope.org/Collectors/Zope/1724

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= Request - Entry #1 by slinkp on Mar 14, 2005 2:06 pm

This is copied from a thread on zodb-dev:
http://mail.zope.org/pipermail/zodb-dev/2005-March/008582.html

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?                                                              

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