[storm] RuntimeError with Storm(twisted integration)

[Daniel Yang]

Thank.That works.

On Mon, Jul 20, 2009 at 4:24 AM, Drew Smathers <drew.smathers at gmail.com>wrote:

> On Fri, Jul 17, 2009 at 3:14 AM, Daniel
> Yang<daniel.yang.zhenyu at gmail.com> 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.
>
>
> 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
>



-- 
-----------------------------------------------
Yours
Faithfully

Daniel Yang
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