Fun with Internet Plumbing

June 22, 2009

The other day I realized I hate notification emails. In particular I’m talking about SVN commit notifications. I have them set up to skip my inbox and filter into a label on GMail, but this doesn’t really help. They don’t pollute my inbox, but I still have to go out of the way to read them. Or at the very least, mark them as read, which is still quite annoying!

Growl is supposed to help solve this problem. In fact, when I was retooling the notification system at work, I would have loved to integrate Growl … except that Growl’s network interface requires a direct connection.

Taking a step back, it’s not just work notifications. A lot of us get a lot of notification emails about a lot of things. Most of them are poorly designed, for example, without important details of the notice in the subject. Plus, as email they require disrupting action. Not just to open and read if you have to, but just to archive and/or mark as read.

It’s great to have an archive in email, but email is just not ideal for notifications. If I’m around to receive them, I should get the important information passively and not have to do anything else until I need to reference it later, if ever. That means Growl.

Getting Notification Emails to Growl

I thought to myself, “I should be able to rig this up. And it should be easy.” And if the infrastructure and plumbing I’ve wanted was in place, it would be easy. So I decided to lay it down and make it happen. Here’s what I needed:

  • An email to webhook bridge, like my old Mailhook service.
  • An XMPP to Growl bridge. We all want this anyway, right?
  • An HTTP to XMPP bridge. Why? You’ll see.
  • Glue code that can run in the cloud. This is what Scriptlets is for.

I’ve since turned off Mailhook, but I’ve been planning to roll its code into my still early Protocol Droid project. This is an HTTP to anything bridge written in Python with Twisted that makes heavy use of webhooks. I’d plan to roll the HTTP to XMPP bridge in there as well. For now, the XMPP to Growl bridge would be separate.

Having all that, here was the pipeline I envisioned:

  • A notification email would come into Gmail and get filtered
  • It would forward to an address that points to Protocol Droid
  • Protocol Droid would post the email to a script on Scriptlets
  • The script would use Protocol Droid again to send an XMPP message
  • The message would be sent to a JID for my laptop if online
  • The XMPP to Growl bridge on my laptop would receive and notify me

Building the Infrastructure

I decided to build all this last Friday night. I got caffeinated and went to work, starting with Protocol Droid. I hadn’t touched it since I was trying to build an HTTP to SMTP module for it. It wasn’t part of this project, but I decided to finish it off. You know, to get warmed up and have an early win.

That happened pretty quickly, so I was excited get started on the next task: an email to webhook bridge. This was a little different. So far everything in Protocol Droid was for outgoing connections. This would be the first listening module. The idea was that it would be an SMTP server that would parse incoming email and post it to a callback URL registered for a recipient domain. I’d written several of these before for, so I ported the code to Twisted for Protocol Droid. Another pretty easy win. I used PostBin to debug this, obviously.

At that point, I decided to take a break and watch an episode of Pushing Daisies. I still haven’t seen all of the second season!

Then came the hard part. Well, I thought it would be easy. The HTTP to XMPP bridge. It turns out the XMPP support in Twisted isn’t very well documented and slightly underdeveloped. I had to build a couple of prototypes to get the hang of it. Even then, building this module and the XMPP to Growl daemon took about 7 hours! Compared to the 3 hours spent doing the last two modules. XMPP is definitely a bit hard to really get into.

By 8am I had all the pieces working. I thought about going the last mile and getting it all online and set up the pipeline … but I decided I deserved some sleep. I’d do it when I wake up.

Getting the Pipeline in Place

When I woke up on Saturday, I was still burnt out from coding. I spent the day hanging out with friends. Then later I invited some more friends over for hacking at my place. There I spent more time than I wanted getting my code to run on my server. Apparently OpenSSL for Python wasn’t installed and the Google Talk servers required TLS. It took a while to figure this out since no error was raised and Google would just drop my connection.

I finally got all the infrastructure I built online and tested. Finally, I could work on the actual pipeline. It was supposed to be easy from that point on. And it was! Except for one bit …

I got almost all the pieces connected and it all came down to the glue code on Scriptlets. The script would parse the email however I like and set up the message that would end up on my laptop via Growl. It turns out Scriptlets is a bit of a pain to use. No edit, no debugging, crappy error messages. Since I built it as a proof of concept, I hadn’t done much development on it, let alone with it. Anyway, I learned a lot and have some things to fix. But! I was still able to get everything working!

I had my friend Adam send the first test email that would go through the entire pipeline I outlined above. He sent it from his phone, just to add a little to the magic. Low and behold, it worked perfectly, quite quickly. It took 4 seconds from him sending to the notice appearing … but about 3 of those seconds were the time it took for the phone to send the email. Nevertheless, brilliant!

Next Steps

I’ve since found out about Wokkel, which might simplify some of my XMPP code. I have some other enhancements to make to each piece to make them more general. And I mentioned some of the things I need to add to Scriptlets.

Functionally, the pipeline is pretty good. The only addition I can think of would require an HTTP to IMAP bridge in Protocol Droid (something I’ve already prototyped). I’d use this to mark the notification email as unread if it wasn’t able to deliver the IM. But for now, I think I’m done on this project. And you can all take advantage of the infrastructure I built out for rigging up your own cool hacks.

Most of the code this weekend went into these two projects, so check them out!

2 Responses to “Fun with Internet Plumbing”

  1. AquaRescue Says:

    ha, email notifications, tottaly good stuff !!!

  2. Ha here I was thinking there was some new plumbing guide online, now I have had a lesson in internet plumbing! Actually very interesting post.

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