[Zope3-dev] Re: ZOPE3 Maildir implementation

[Marius Gedminas]

Hi, folks!

On Fri, Apr 07, 2006 at 05:23:06PM +0200, Philipp von Weitershausen wrote:
> > The Maildir step could have been skipped, I suppose, just the
> > connection to a mail server directly over the network interface would
> > suffice. Is there a specific reason for the Maildir implementation?
> 
> The reason for queued delivery (as opposed to direct delivery) is that
> you might send an email that is later aborted. For example, consider a
> change notification email whereas the change itself is aborted. The
> email would be lying about the state of the application. With queued
> delivery, the email isn't sent when the transaction is aborted.
> As Gary pointed out, the reason for using Maildir is a practical one. We
> don't want to block.

Actually, the DirectMailDelivery utility also aborts emails if the
transaction is aborted.  The reason for using Maildirs was to speed up
the transaction commit -- if you send 100 emails in a transaction, you
do not want to wait for 100 SMTP connections while the user is sitting
in front of his browser waiting.  Creating a 100 files in the outgoing
mail queue was supposed to be faster.

It didn't work due to the extreme brain-deadness of the Maildir code.
IIRC I wrote it (a number of years ago, when I was young and foolish)
and I cannot fathom why I didn't realize that 1 email per second would
be an extremely inconvenient.  Maybe I was too enamored with Extreme
Programming ideas at the time (let's do the simplest thing that could
possibly work, and when it turns out to be not enough, we can just fix
it).  Well, the time to fix it has finally come.

There were also some bugs in the transaction commit/abort logic that
could lead to multiple copies of the emails being sent on ZODB
ConflictErrors.

Thankfully all this is now fixed in Zope 3 trunk, and in the 3.2 branch.
The issue was http://www.zope.org/Collectors/Zope3-dev/590

> > 2. The current implementation can only handle between 30-60 E-mail's a
> > minute. This is mostly due to the naming convention used for maildir
> > files (one a second - actually the Maildir naming allows in between
> > numbers, but you don't use that).
> 
> Actually, the Maildir spec (http://cr.yp.to/proto/maildir.html) now
> suggests "new fashion" Maildir names that are a lot "more unique" than
> old fashion ones. Every major Maildir implementation I've come across in
> the last two years uses new fashion Maildir names.

I didn't know about this.  Yesterday I just changed the unique name
generator to include a large random number in the filename.  In the
wrong place, so it no longer matches the Maildir spec.  *sigh*

Any volunteers for making it match the spec?

Marius Gedminas
-- 
#define QUESTION ((bb) || !(bb)) /* Shakespeare */
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