Introducing the Dramble - Raspberry Pi 2 cluster running Drupal 8

Dramble - 6 Raspberry Pi 2 model Bs running Drupal 8 on a cluster
Version 0.9.3 of the Dramble—running Drupal 8 on 6 Raspberry Pis

I've been tinkering with computers since I was a kid, but in the past ten or so years, mainstream computing has become more and more locked down, enclosed, lightweight, and, well, polished. I even wrote a blog post about how, nowadays, most computers are amazing. Long gone are the days when I had to worry about line voltage, IRQ settings, diagnosing bad capacitors, and replacing 40-pin cables that went bad!

But I'm always tempted back into my earlier years of more hardware-oriented hacking when I pull out one of my Raspberry Pi B+/A+ or Arduino Unos. These devices are as raw of modern computers as you can get—requiring you to actual touch the silicone chips and pins to be able to even use the devices. I've been building a temperature monitoring network that's based around a Node.js/Express app using Pis and Arduinos placed around my house. I've also been working a lot lately on a project that incorporates three of my current favorite technologies: The Raspberry Pi 2 model B (just announced earlier this month), Ansible, and Drupal!

In short, I'm building a cluster of Raspberry Pis, and designating it a 'Dramble'—a 'bramble' of Raspberry Pis running Drupal 8.

Motivation


This LED will light up that wonderful Drupal Blue, #0678BE

I've been giving a number of presentations on managing infrastructure with Ansible in the past couple years. And in the course of writing Ansible for DevOps (available on LeanPub!), I've done a lot of testing on VMs both locally and in the cloud.

But doing this testing on a 'local datacenter'—especially one that fits in the palm of my hand—is great for two reasons:

  • All networking is local; conferences don't always have the most stable networking, so I can do all my infrastructure testing on my own 'local cloud'.
  • It's pretty awesome to be able to hold a cluster of physical servers and a Gigabit network in my hand!

Lessons Learned (so far!)


Drool... I own these!

Building out the Pi-based infrastructure has taught me a lot about small-scale computing, efficient use of resources, benchmarking, and also how Drupal 8 differs (spoiler: it's way better) from Drupal 7 in terms of multi-server deployment and high-availability/high-performance configurations.

I've also learned:

Benchmarking


Wiring up the mini Cat5e network cables.

I've been benchmarking the heck out of this infrastructure, and besides finding that the major limiting factor with a bunch of low-cost computers is almost always slow I/O, I've found that:

  • On-the-fly gzip actually harms performance (in general) when your CPU isn't that fast.
  • Redis caching gives an immediate 15% speedup for Drupal 8.
  • Different microSD cards deliver order-of-magnitude speedups. As an example, one card took 20 minutes to import a 6MB database; another card? 9 seconds.
  • Drupal 8 is kinda slow (but I don't need to tell you that).
  • Still to come: Nginx vs. Apache with php-fpm, Nginx vs. Varnish for load balancing, Redis vs. Memcached for caching. MySQL vs. MariaDB for database. And more!

Since I have this nice little cluster of Raspberry Pis humming along using half the power of a standard light bulb, the sky is the limit! And the fact that the servers are slower and have different performance considerations than typical modern cloud-based infrastructure actually helps to expose certain performance-related flaws that I wouldn't have otherwise!

Finally, it helps me stay creative in finding ways to eke out another 50 KB/sec of bandwidth here, or 100 iops there :)

See the Dramble in person!

So why am I mentioning all this? Because I want to bring the Dramble with me to some Drupal events, and I'd love to share it with you, explain everything in more detail, and most importantly: demonstrate modern and easy Drupal 8 deployment with Ansible on it.

I'll be bringing it to #MidCamp in Chicago on Saturday, March 21, and I've also submitted a session for DrupalCon LA: Deploying Drupal 8 to Bare Metal with Ansible - Live!

I hope the session is selected and I can bring the Dramble with me to LA in a couple months :)

Also, if you haven't submitted your own session for DrupalCon LA, the deadline is Friday; go submit it now!

For more on the Dramble itself, check out the Raspberry Pi Dramble project on GitHub, and see what I'm working on over in the Dramble issue queue.

Comments

It would be really cool, if you can assign each Raspberry Pi with a LED, and light it up when a Raspberry Pi is processing one request. More particularly, when a client initializes a HTTP request, then first the load balancer LED lights up, then one of the Drupal heads lights up, then either redis starts blinking and/or database starts blinking (each request is one blink).

Something along those lines, at least... https://github.com/geerlingguy/raspberry-pi-dramble/issues/45

This is really nice work. Do you happen to have a parts list for those of us who selfishly want to take advantage of your excellent project?

I'm glad you asked! See this section in the project README on GitHub.

What sd cards do you recommend for fast performance :D

Please see my microSD card performance benchmarks: https://github.com/geerlingguy/raspberry-pi-dramble/wiki/microSD-Card-Be...

Hey Jeff,

I'm new to your site and almost as new to the world of RPi. I just started coding in Python (mostly crawlers/ auto-plotting graphs via os.system, etc) and was wondering if you have good resources (links?) for someone interested in learning more about Drupal. I know I could google around, but I'd like to hear what an expert considers the best course of action.

Thanks!

PS: I second what skyred suggested about adding LEDs to each Pi!

nice project, have you tried webhosting on your cluster of pis, is the performance of the cluster better than say a individual server?

I run Drupal 8 on the cluster for testing purposes, and the entire cluster of 6 Pis is still a little bit slower than one 2 GB RAM VM on DigitalOcean, or my i7 MacBook Air laptop running an Ubuntu VM... so no, it's not faster. But yes, it's great for educational/testing/fun purposes!

And it's not that it'd be terrible as a website hosting cluster, it's just that disk read/write is comparatively slow, the I/O is limited (couldn't handle large traffic spikes), and the Pi wasn't designed to be a forever-on high-performance device. Better to let it do less resource-intense tasks if you want to leave it running 24x7.

Greetings see if I try to create virtual servers as raspberry could help , I need to create 03 two Linux servers ( proxy - fileserver ) and Windows2008 (ad )

It is clearly evidence sized amount of raspberry need plates and it would help me use both SATA drive via USB as SD cards are so slow .

Greetings from Peru
Dante Aguirre

Is there a hardware list available for your project. I am interested in what you used for the stackable cases as well as the USB power adapter.

Yes; the project has a wiki with the exact parts list (prices and links included): Parts list: Raspberry Pis and accessories.