EC2 Monitoring with Raspberry Pi

I’ve been doing a little Raspberry Pi hacking lately, and put together a neat way to have physical status LEDs on your desk for things like EC2 instances.

The Hardware

In its most basic form, you can simply hook up an LED and a bias resistor between a ground line and a GPIO line on the Pi, but that doesn’t scale especially well – You can run out of GPIO lines pretty quickly, especially if you’re doing different colors for each status. Plus, it’s not overly elegant.

The solution? Unicorns!

No, really. The fine folks at Pimoroni in Sheffield, UK have made a lovely little HAT device for the Pi called a Unicorn. Its primary purpose is lots of blinky lights to make pretty rainbows and stuff, hence the name. However, this HAT is a 4×8 (or an 8×8) array of RGB LEDs, addressable via the I2C bus, which doesn’t eat up a line per LED (good thing, otherwise it would require 96 analog lines). The unicornhat library (python3-unicornhat) is available for Python 2 and Python 3 in the Raspbian repo. When installed onto the Pi, the Unicorn will fit within a standard Raspberry Pi case.

The Code

This is my first foray into Python, so there was a bit of a learning curve. If you’re familiar with object-oriented code concepts, this should be easy for you. Python is much more parsimonious with punctuation than PHP or perl are.

For accessing the EC2 data, we’ll need Amazon’s boto3 library, also available in the Raspbian repo (python3-boto). One area where boto3 is really nice is that the data is returned directly as a dict object (what users of other languages would call an array), so you don’t have to mess with converting JSON or XML into an object structure, and it can be manipulated as you would any other associative array (or a hash for you old-timers that use perl). AWS returns a fairly complex object, so you kind of have to dig into it via a few iterative loops to extract the data you’re after.

From there, it’s a matter of assigning different RGB values to the states. I chose these ones:

  • stopped: red
  • pending: green
  • running: blue
  • stopping: yellow(ish)

I also discovered that I needed to assign a specific pixel to each instance ID, otherwise they tended to move around a bit depending on what order AWS returned them on a particular request.

Here’s what the second iteration looks like in action:

import boto3 as aws
import unicornhat as unicorn
import time

# Initialize the Unicorn

# Create an EC2 object 
ec2 = aws.client('ec2')

# Define colors and positions
color = {}
pixel = {}

# Loop until forever
while True:

	response = ec2.describe_instances()
	statetable = {}
	resarray = response['Reservations']
	for res in resarray:
		instarray = res['Instances']
		for inst in instarray:
			iid = inst['InstanceId']
			state = inst['State']['Name']
			# print(iid)
			# print(state)
			statetable[iid] = state
	for ec2inst in statetable:
		x = pixel[ec2inst]['x']
		y = pixel[ec2inst]['y']
		r = color[statetable[ec2inst]]['red']
		g = color[statetable[ec2inst]]['green']
		b = color[statetable[ec2inst]]['blue']
		# print(x,y,r,g,b)


For the moment, this is just monitoring EC2 status, but I’m going to be adding checks in the near future to do things like ping tests, HTTP checks, etc. Stay tuned.

HLS distribution with Amazon CloudFront

I’ve blogged extensively about Wowza RTMP distribution with edge/origin and load balancing, but streaming distribution is moving more to HTTP-based systems such as Apple’s HTTP Live Streaming (known inside Wowza as “cupertino”), Adobe’s HTTP Dynamic Streaming (Wowza: “sanjose”), and Microsoft’s Smooth Streaming (Wowza: “smooth”). Future trends suggest a move to MPEG-DASH, which is a standard based on all three proprietary methods (I’ll get into DASH in a future post as the standard coalesces – we’re talking bleeding edge here). The common element in all of them, however, is that they use HTTP as a distribution method, which makes it much easier to leverage CDNs that are geared towards non-live content on HTTP. One of these CDNs is Amazon’s CloudFront service. With edges in 41 locations around the world and 12 cents a gigabyte for transfer (pricing may vary by region), it’s a good way to get into an HTTP CDN without paying a huge amount of money or committing to a big contract with a provider like Akamai.

On the player side, JW Player V6 now supports HLS, and you can do Adobe HDS with the Strobe Media Player.

With the 3.5 release, Wowza Media Server can now act as an HTTP caching origin for any HTTP based CDN, including CloudFront. Doing so is exceedingly simple. First, configure your Wowza server as an HTTP caching origin, and then create a CloudFront distribution (use a “download” type rather than a streaming type – it seems counterintuitive, but trust me on this one!), and then under the origin domain name, put the hostname of your Wowza server. You can leave the rest as defaults, and it will work. It’ll take Amazon a few minutes to provision the distribution, but once it’s ready, you’ll get a URL that looks something like “”. You can verify that the distribution is working by opening a browser to that address, and you should see the Wowza version information. Put that same CloudFront URL in the player URL in place of the Wowza server address, and your players will now start playing from the nearest CloudFront edge cache.

See? Easy.