[Zope] Design around conflict errors

[Jeff Youel]

I've created an object to record some information (datetime, url,
username) for each file downloaded from the site for later searching
(CMF 1.3.1, Zope 2.6.1).  To do this, I have a BTreeFolder with a
private ZCatalog and put an new instance of a DownloadRecord object (my
own object that just has string members holding the fields to be queried
later) into the folder when the file is requested.  

I'm running into conflict errors; I think because the download record
object is added to a single folder so concurrent downloads on different
threads are competing trying to modified the folder.  Because the
downloads will take a while (they're 1-5 MB), the transaction is not
committed until the download is complete.  With a large download it
seems that window for conflicts is large.

I've been googling and reading about conflict errors but haven't found a
solution yet.  I've tried committing the a sub-transaction but that
didn't help.

I'm thinking of committing the default transaction before sending the
file, but I'm not sure of the implications of doing that.

Any ideas?

Thanks,
Jeff