Thank.<div>That works. <div class="gmail_quote">On Mon, Jul 20, 2009 at 4:24 AM, Drew Smathers <<a href="mailto:drew.smathers@gmail.com">drew.smathers@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> <div><div></div><div class="h5">On Fri, Jul 17, 2009 at 3:14 AM, Daniel Yang<<a href="mailto:daniel.yang.zhenyu@gmail.com">daniel.yang.zhenyu@gmail.com</a>> wrote: > Hi team, > I am doing some experiments on Storm(twisted integration) and Nevow to see > how they can work together. > I went across a RuntimeError when I kept refreshing a page. It said: > ------------------------------------------------log-------------------------------------------------------------- > 2009-07-17 14:58:42+0800 [-] [Failure instance: Traceback: <type > 'exceptions.RuntimeError'>: Resolving lazy values with the Twisted wrapper > is not possible right now! Please refetch your object using > store.get/store.find > --- <exception caught here> --- > /Library/Python/2.5/site-packages/Twisted-8.2.0_r27097-py2.5-macosx-10.5-i386.egg/twisted/internet/defer.py:323:_runCallbacks > /Users/Daniel/Documents/workspace/NovaWeb/src/web/FromLocation.py:47:cb_all > /Library/Python/2.5/site-packages/storm-0.14-py2.5-macosx-10.5-i386.egg/storm/properties.py:60:__get__ > /Library/Python/2.5/site-packages/storm-0.14-py2.5-macosx-10.5-i386.egg/storm/variables.py:178:get > /Library/Python/2.5/site-packages/storm-0.14-py2.5-macosx-10.5-i386.egg/storm/event.py:53:emit > /Library/Python/2.5/site-packages/storm-0.14-py2.5-macosx-10.5-i386.egg/storm/twisted/store.py:238:_resolve_lazy_value > ] > ------------------------------------------------log-------------------------------------------------------------- > (latest storm and Nevow, Twisted.Python 2.5.1, Osx 10.5.7) > I am using StorePool to manage connections: > ------------------------------------------------code-------------------------------------------------------------- > > from storm.databases.sqlite import SQLite > > from storm.uri import URI > > from storm.twisted.store import StorePool > > database = SQLite(URI('sqlite:///test.db')) > > pool = StorePool(database, 5, 10) > > pool.start() > > ------------------------------------------------code-------------------------------------------------------------- > > > On this page, I have 2 renders to access database(sqlite) with storm(People > list and Shop list): > > ------------------------------------------------code-------------------------------------------------------------- > > def render_PeopleList(self, ctx, data): > > pat = inevow.IQ(ctx).patternGenerator('PeopleItem') > > def cb_find(results, s): > > results.config(offset=0, limit=10) > > return results.all().addCallback(cb_all, s) > > def cb_all(items, s): > > #recycle the store. > > pool.put(s) > > ps = [] > > for item in items: > > p = pat() > > p.fillSlots('nickname', item.nickname) > > ps.append(p) > > return ctx.tag[ ps ] > > def cb_get(s): > > return s.find(People).addBoth(cb_find, s) > > return pool.get().addCallback(cb_get).addErrback(lambda error: > log.msg(error)) > > ------------------------------------------------code-------------------------------------------------------------- > and shop render is pretty much like this. > > In file "storm/twisted/store.py:238", I notice the _resolve_lazy_value > function does nothing but raising an error. > Do anyone have any idea of what is the problem? > Thanks. </div></div>This is the problem: pool.put(s) ... doing something with object from store `s' Once you put a store back in the pool this will effectively rollback the store. Now being in a new transaction, referring to an attribute on the object will try to load the most recent data from the store to enforce "serializable" semantics. twisted-integration can't manage this because attribute access isn't can't be deferred in the store's thread -- without necessitating a very awkward API. I think some good practices to avoid lazy value errors are: 1. Do everything you need to with objects before putting store back in pool and then discard those objects 2. Re-fetch objects if you have done any inserts/updates (in same tx) before referencing attributes on them 3. If you need to keep references lying around (caching as an example), create read-only version of those objects which aren't attached to store. Lastly, unrelated to you core problem, but this code looks like a unit test for twisted-integration. The tests are written to be compatible with older versions of Python, so you may consider using inlineCallbacks() to make your life easier if your deployment target is 2.5>. There is also a transact() method which takes care of putting the store back in pool after your function exits. An example using inlineCallbacks() and transact(): from twisted.internet.defer import inlineCallbacks, returnValue @inlineCallbacks def transaction(store, offset, limit): dr = yield store.find(People) dr.config(offset=offset, limit=limit) items = yield dr.all() for item in items: ... do stuff with item # commit tx if you've changed objects yield store.commit() returnValue(ctx_tag[ps]) pool.transact(transaction, 0, 10) -- \\\\\/\"/\\\\\\\\\\\ \\\\/ // //\/\\\\\\\ \\\/ \\// /\ \/\\\\ \\/ /\/ / /\/ /\ \\\ \/ / /\/ /\ /\\\ \\ / /\\\ /\\\ \\\\\/\ \/\\\\\/\\\\\/\\\\\\ d.p.s </blockquote></div> -- ----------------------------------------------- Yours Faithfully Daniel Yang </div>