My Own Private CDN

Hosting my own CDN has long been a completely irrational goal of mine. Wouldn't it be neat, I'd think, if I could tweak every knob instead of relying on CloudFront to do the right thing? Recently I read this article by Janos Pasztor about how he built a tiny CDN for his website. This just proves to me that at least it's not an uncommon irrational thought.

Yesterday I decided to actually start building something. Even if it doesn't make it into production, I'll at least have learned something.

Technical Goals

• Centrally manage all of the dozen or so sites that I run
• Automatically generate and renew LetsEncrypt certificates, both for publicly-facing sites and my own private sites. This means using the dns-01 challenge instead of using the easier to understand http challenge.
• Easily add new cache nodes with authenticated curl | sudo bash
• Automatically reconfigure nginx on the cache nodes when certificates roll or sites change
• Easily host sites anywhere, including the internet-inaccessible server in my basement
• Stop paying so much for bandwidth. Transfer is $5/tb/mo from DigitalOcean vs $$$$ for CloudFront.

Additionally, I really want to learn how LetsEncrypt works. certbot is great but it is very much a black box to me. Command-line arguments in, certificates out. If I write my own management system I can actually learn how the guts work.

Current Status

• basic Rails app that knows about sites and proxies
• creating or updating a site (re)generates a LetsEncrypt certificate for all of the domains that point at that site
• wildcard domains are fully supported
• authenticated endpoint that generates a zip file of all of the certificates and private keys

Next Steps

• Automatic certificate refresh using something like Sidekiq Cron
• Deploy onto the server in my basement on my ZeroTier network
• Move all of my existing LetsEncrypt certbot crons into this system
• Provision a POP by hand and then automate the steps to provision another one

If you'd like to follow along I put the project up on GitHub. I'll also be posting updates here as I go.

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