I didn’t ask for them. Yes, the code is intended to make them. But I did not trigger code to make them. So why were photos spawning in my S3 Bucket the other day?

Let’s go over some context first. Yesterday, I expanded on my Udacity Meme Generator project. I’m taking it out of local deployment and into the cloud. The purpose of this site is to take random photos and random quotes and turn them into random memes. The source photos and resulting memes are stored in an S3 Bucket. The code is run on Ec2 instances. The Ec2 instances are in an autoscaling group behind a load balancer. The Cloud Formation YAML file can be viewed here.

My task yesterday involved experimenting with fonts. I wanted the Ec2 instances to pull fonts from the same S3 bucket. I created several test scripts to get it right. And while testing, I expected a dozen or so random memes generated in my s3 bucket. Instead, I saw hundreds.

Unsure how that happened, I cleared them out of the folder. Then, ssh’ed into one Ec2 instance and continued my work. As I generated memes with the new fonts, I noticed more random memes generated with the old font, and worse, it looked like they were generated from the website. I wasn’t loading the website so I still didn’t get it.

I deleted the spawned memes again. Then I wondered if someone was trolling my application, but that seemed unlikely. I thought my test files might have made multiple calls, or somehow recursing over themselves. Not happening.

Finally, I looked at my Cloudformation YAML file. At the time this problem was happening, the health check looked like this:

While my Flask application looked like this (is intended behavior).

Can you see the issue here?

I followed the KISS method in setting up the original health check. It called root, which is essentially checks, “hey, can you load this page yet?” The Ec2 instance could load that page. It was, therefore ‘healthy’. It therefore also created a new meme, and put it into the s3 bucket.

Health checks are repeated checks, and these repeated checks found healthy instances, and those instances repeatedly spawned memes.

To fix this, I made a proper health check. The YAML was changed to this:

And then I added another KISS method health check like this

And now the memes only spawn when I tell them to.