Fly.io ❤️ Bun

Bun 1.0 comes out September 7th. Fly.io is making preparations.

Previously, we stated that Fly.io ❤️ JS, and we understandably started with Node.js. While that work is ongoing, it makes sense to start expanding to other runtimes.

Bun is the obvious next choice given it aims for complete Node.js API compatibility.

Starting with flyctl version 0.1.54 and @flydotio/dockerfile version 0.3.3, you can launch and deploy bun applications using fly launch and fly deploy, provided:

• You’ve installed bun version 0.5.3 or later
• You have a package.json that meets at least one of the following conditions:
  • It has a start entry in the scripts section.
  • It has a module entry and specified module as the type.
  • If has a main entry.

Basically, if you can run Bun’s Quickstart and Fly’s hands-on walk-through, you have all you need to deploy your application on fly.io.

We also have a sample that you can deploy.

Be forewarned that everything is beta at this point. Some issues we encountered while preparing this support:

• bun install has no --prune option. Our Dockerfiles use this to remove development dependencies after running build. Of course with bun you are less likely to need a build step as TS and JSX are built in.
• throwIfNoEntry is not supported in fs.statSync. fly-apps/node-demo uses that.
• Programs that used readline never exit. Switching to global.prompt resolved this issue for @flydotio/dockerfile.

Undoubtedly there will be bugs in fly’s dockerfile generator too. But as Node.js and Bun share the same generator, fixes that are made for either framework will generally benefit both.

If you see a problem, start a discussion, open an issue, or create a pull request.