Simon Willison’s Weblog

Multi-region PostgreSQL on Fly (via) Really interesting piece of architectural design from Fly here. Fly can run your application (as a Docker container run using Firecracker) in multiple regions around the world, and they’ve now quietly added PostgreSQL multi-region support. The way it works is that all-but-one region can have a read-only replica, and requests sent to application servers can perform read-only queries against their local region’s replica. If a request needs to execute a SQL update your application code can return a “fly-replay: region=scl” HTTP header and the Fly CDN will transparently replay the request against the region containing the leader database. This also means you can implement tricks like setting a 10s expiring cookie every time the user performs a write, such that their requests in the next 10s will go straight to the leader and avoid them experiencing any replication lag that hasn’t caught up with their latest update.

# 17th June 2021, 6:39 pm / postgresql, replication, scaling, fly

Sandboxing and Workload Isolation (via) Fly.io run other people’s code in containers, so workload isolation is a Big Deal for them. This blog post goes deep into the history of isolation and the various different approaches you can take, and fills me with confidence that the team at Fly.io know their stuff. I got to the bottom and found it had been written by Thomas Ptacek, which didn’t surprise me in the slightest.

# 30th July 2020, 10:19 pm / sandboxing, security, thomas-ptacek, docker, fly

How CDNs Generate Certificates. Thomas Ptacek (now at Fly) describes in intricate detail the challenges faced by large-scale hosting providers that want to securely issue LetsEncrypt certificates for customer domains. Lots of detail here on the different ACME challenges supported by LetsEncrypt and why the new tls-alpn-01 challenge is the right option for operating at scale.

# 26th June 2020, 12:03 am / acme, certificates, domains, thomas-ptacek, tls, fly

Making Datasets Fly with Datasette and Fly (via) It’s always exciting to see a Datasette tutorial that wasn’t written by me! This one is great—it shows how to load Central Park Squirrel Census data into a SQLite database, explore it with Datasette and then publish it to the Fly hosting platform using datasette-publish-fly and datasette-cluster-map.

# 26th March 2020, 11:56 pm / tutorials, datasette, fly

datasette-publish-fly (via) Fly is a neat new Docker hosting provider with a very tempting pricing model: Just $2.67/month for their smallest always-on instance, and they give each user $10/month in free credit. datasette-publish-fly is the first plugin I’ve written using the publish_subcommand plugin hook, which allows extra hosting providers to be added as publish targets. Install the plugin and you can run “datasette publish fly data.db” to deploy SQLite databases to your Fly account.

# 19th March 2020, 3:40 am / hosting, projects, docker, datasette, fly