[Catalyst] Sending email safely with Catalyst

[Dave Rolsky]

On Fri, 11 Apr 2008, Jonathan Rockway wrote:

> In an ideal world, you should be able to dump the messages into your
> mail system's queue as quickly as you can dump them into a database
> table (adding to the mail queue is a disk write, adding to a database is
> a disk write, unless you've turned off data integrity).
>
> I could see how calculating the text of 10000 mail messages during a
> request would be slow, but why would you want to do that?  Usually
> you'll just want to say "Your account was created, [% name %]!" and
> queue that.  The template rendering and the mail system's queue should
> be more than fast enough to handle that during a request.
>
> As for bulk emails, you probably have a process that calculates those
> outside of your Catalyst app anyway (running from cron), so calculate
> them, dump them into the mail queue, and let your mailer daemon figure
> out what to do.  Much better than putting a queue in front of a queue,
> IMHO.  This is UNIX after all.

The big problem I've run into when sending lots of emails from a web app 
(just hundreds, in this case), is that it can be slow enough the browser 
times out.

Presumably you could have a similar problem with a work queue as well.

Ultimately, I suspect a solution that forks _immediately_ and then does 
its thing (whatever that thing may be) is going to be necessary past a 
certain scale.

Then the trick becomes monitoring that forked process.

Another solution might be to come up with a way to queue up the job with a 
single write and do the full email generation via cron. Either way, you 
have to add complexity to your app if you want to provide feedback on the 
job status to the user.

I'll be working on this soon for an app I'm creating, and I suspect I'll 
go the route of doing a single insert and processing via a cron job. The 
upside of this is that for a multi-user app, I won't end up forking a 
whole bunch of email sending processes and I can exercise some control 
over the rate that email is generated.


-dave

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