[Zope] Problem with constructTransientObjectContainer - Resolved

[Jonathan]

----- Original Message ----- 
From: "Chris Withers" <chris at simplistix.co.uk>
To: "Jonathan" <dev101 at magma.ca>
Cc: "Chris McDonough" <chrism at plope.com>; <zope at zope.org>
Sent: Wednesday, June 21, 2006 6:25 AM
Subject: Re: [Zope] Problem with constructTransientObjectContainer - 
Resolved


> Jonathan wrote:
>>
>>        folder = self.restrictedTraverse('Coz/TempImages')
>>        constructTransientObjectContainer(folder, 'GarbageCollector', 
>> timeout_mins=10, limit=0,
>>                delNotification=BASEFOLDER+'DeleteTempImage')
>
> Be careful, I see a lot of hints in there that make me nervous. I'm of the 
> opinion that if you think you need to use a TOC, you're probably doing 
> something wrong...

The use case:  the zodb contains small image objects which need to have a 
custom overlay (done with PIL) before being presented to the user.  Each 
overlay is unique.  Each customized image is only shown to a single user 
once, then it is discarded.  In order to eliminate many writes to the zodb 
(disk), I have decided to put the customized images into a temporary folder 
(RAM).  In order to delete the customized images I have created a TOC to act 
as a 'GarbageCollector'.  Whenever a customized image is written to the 
temporary folder, an entry containing the image object id is placed in the 
TOC.  When the TOC 'times-out' an entry a script (external method) acquires 
the object id from the TOC entry and deletes the customized image from the 
temporary folder.

This seems to be working... so far ;-)

What 'hints' are making you nervous?  Is there a 'better' way to do this?


Jonathan