On Wednesday 23 December 2009 20:26:13 Jim Fulton wrote: > Undo is broken in a number of ways. Does anyone care? Does anyone use > undo?
First, a disclaimer: what I state below is from Zope 2.8-ish experiences, with its original ZODB version. I hope my mail is still on topic nevertheless. In my company, it is gradually becoming a production-server-setup step to disable (remove via monkey patch) the "undo" tab from Zope's ZMI, because it happens quite often for someone to click on it on a multi-gigabyte FileStorage via Zeo, causing the whole cluster to go down until someone restarts Zope & Zeo or a few hours pass. This is due to the backward seeking done when listing transactions to undo (disk throughput goes down to a crawl) filtered by context path (depending on the path, the given limit of transactions to display will never be reached) and with storage lock taken, effectively bringing the cluster down. So I believe that this performance issue, although being less serious than what you present as technical breakage, is a showstopper by itself in practise (unless it becomes impossible to filter transactions to undo, making the action end in a roughly constant time for a given transaction number). Maybe this would be an argument toward offline-only undo support. Finally, I believe that undo feature is miss-represented in Zope (keep above disclaimer in mind: I don't know about most recent Zopes), because most people I know who used that "undo" tab are actually interested in undoing transactions modifying context, not transaction done on context (so they actually want to use the efficient "history" tab, the one using FileStorage object version back-pointers). -- Vincent Pelletier _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - [email protected] https://mail.zope.org/mailman/listinfo/zodb-dev
