Deploying SvelteKit Apps on Fly.io

Ok, so I went over this in this in a post a while back. I was having issues deploying a SvelteKit app to Fly.io. The reasoning behind me wanting to use Fly is so that I can put the projects near where the users are, reducing latency and giving an all round better experience. In this case it’s for a proof of concept more than anything else before I start using Fly for other projects. My ideal is so that I can use Turso (which can also be used on serverless platforms like Vercel) then use an embedded replica for zero latency reads and writes (which you can’t do on a serveless platform like Vercel).

Once the app is built and deployed on Fly I then want to assign a domain to it.

Two relatively simple steps when you think about it, right? Well, the most frustrating part was actually getting the Docker project to build for Fly.

The setup

What I wanted to do is have a SvelteKit app that uses Lucia auth and Turso. So, go through the Lucia auth tutorial to set it up using Turso for the database.

Additional dependencies on top of the SvelteKit skeleton:

"@libsql/client": "^0.5.6",
"@lucia-auth/adapter-sqlite": "^3.0.1",
"@sveltejs/adapter-node": "^5.0.1",
"lucia": "^3.1.1",
"oslo": "^1.1.3"

There’s also Tailwind CSS and daisyUI (standard for me), but irrelevant for this post.

Check the links for specifics for how I’ve implemented it for my app (Rinku Cloud) and the Lucia docs and example code.

• Rinku Cloud repo
• Lucia docs guide
• Lucia GitHub example repo

It’s essentially the SvelteKit skeleton with Lucia auth and Turso added, so this should be a piece of piss to do, right?

Well…

Fly Config

So, to get the project on Fly there’s a couple of steps, two, yes. Anyway, install the Fly CLI and login, then fly launch to have the project configured. Then fly deploy to deploy the project.

First up, fly launch does most of the configuration for you, it installs @flydotio/dockerfile and creates the following files:

.dockerignore
Dockerfile
fly.toml

If you’re in the UK and the CLI configures lhr for the primary_region in the fly.toml file change it! 😅 I had so many build issues with the lhr region that I now just don’t bother with it and now set it to primary_region = 'iad'. I can add another region later once the project builds.

Secrets

Ok, so, add in the secrets for the project, I have two secrets for the project:

TURSO_DB_AUTH_TOKEN=my-super-secret-auth-token
TURSO_DB_URL=my-turso-db-url

From previous experience I now add these as environment variables in my terminal:

export TURSO_DB_AUTH_TOKEN=my-super-secret-auth-token
export TURSO_DB_URL=my-turso-db-url

This means that I’m not copy pasting secrets to the terminal repeatedly and just use a variable like $TURSO_DB_URL.

I need to set the secrets in the Fly project from the Fly CLI:

fly secrets set TURSO_DB_AUTH_TOKEN=$TURSO_DB_AUTH_TOKEN
fly secrets set TURSO_DB_URL=$TURSO_DB_URL

Now I can use fly deploy to deploy the project, right?

Well, yeah, but, no!

Building the Docker Project for Fly

This is where the fun started, and when I say fun, what I actually mean is hours of me banging my head against this (for many, many hours).

Because SvelteKit is a compiler I always install dependencies as devDependencies, regardless, I learned from the last post I did about this that the @libsql/client should be installed in regular dependencies due to some ESM/CJS shenanigans.

Wouldn’t build though, I’d keep getting an error that was something along the lines of this:

node:internal/event_target:1062
  process.nextTick(() => { throw err; });
                           ^
Error [LibsqlError]: URL_INVALID: The URL is not in a valid format
    at parseUri (file:///app/node_modules/.pnpm/@[email protected]/node_modules/@libsql/core/lib-esm/uri.js:9:15)

Ok, Fly still can’t read the environment variables, so, try building locally? Building locally I got an error that was something along the lines of RollupError: Unexpected character '\u{7f}', so, again not building for ESM so I have to pick through the packages and find which one is causing the issue.

Wasn’t a massive pain as there was only a couple of additional packages. oslo was the culprit, so I had move that to dependencies along with @libsql/client.

Go again!

Still not building, same URL_INVALID error…

This is pretty much where I was, for a long, long time. I tried so many different configurations with the Dockerfile and passing in the secrets to the terminal.

I had to have the secrets in the Dockerfile and in the fly deploy command. For the Dockerfile I had to have them as build arguments near the top of the file.

# Adjust NODE_VERSION as desired
ARG NODE_VERSION=18.19.0
FROM node:${NODE_VERSION}-slim as base

# Declare build arguments for secrets
ARG TURSO_DB_URL
ARG TURSO_DB_AUTH_TOKEN

LABEL fly_launch_runtime="Node.js"

Then toward the end of the Dockerfile I had to use the build arguments to build the project using the secrets:

# Copy application code
COPY --link . .

# Build application using build arguments
RUN TURSO_DB_URL=$TURSO_DB_URL TURSO_DB_AUTH_TOKEN=$TURSO_DB_AUTH_TOKEN pnpm run build

# Remove development dependencies
RUN pnpm prune --prod

From the terminal I had to pass in the secrets as build arguments as well:

fly deploy --build-arg TURSO_DB_URL=$TURSO_DB_URL --build-arg TURSO_DB_AUTH_TOKEN=$TURSO_DB_AUTH_TOKEN

Success! 🎉

That did it for me this time around, is it correct? I don’t know, but it worked for me so I’m sticking with it! (for now)

Getting set up with a domain on Fly

So, as all developers do, I bought the domain before making the project! 😅

With that out of the way to begin with I could then add that to my Fly project, even though it’s just a login form with a database behind it!

I know up until this point I haven’t really mentioned the Fly.io documentation, this is some of the best documentation out there!

So I follow the documentation here: https://fly.io/docs/networking/custom-domain

Set up a CNAME and A record in Cloudflare.

Type	Name	Content	Proxy Status	TTL
A	rinku.cloud	66.241.125.15	DNS only	Auto
CNAME	www	rinku-cloud.fly.dev	DNS only	Auto

I need to generate SSL certs for both of the records via the Fly CLI!

fly certs add rinku.cloud
fly certs add www.rinku.cloud

Then wait for the cert to be provisioned, I can check on the status with fly certs show rinku.cloud and fly certs show www.rinku.cloud

fly certs show rinku.cloud

I get a helpful prompt to add an AAA record to prove my ownership.

The certificate for rinku.cloud has not been issued yet.

Hostname                  = rinku.cloud
DNS Provider              = cloudflare
Certificate Authority     = Let's Encrypt
Issued                    =
Added to App              = 3 minutes ago
Source                    = fly

You are creating a certificate for rinku.cloud
We are using lets_encrypt for this certificate.

You can validate your ownership of rinku.cloud by:

1: Adding an AAAA record to your DNS service which reads:

    AAAA @ 2a09:8280:1::2e:fa4a:0

I’m also advised to turn off the proxy for the domain in Cloudflare.

Eventually I get my certs setup!

The certificate for rinku.cloud has been issued.

Hostname                  = rinku.cloud
DNS Provider              = cloudflare
Certificate Authority     = Let's Encrypt
Issued                    = rsa,ecdsa
Added to App              = 7 minutes ago
Source                    = fly

I’m all set!

I can now access the app via the domain I’ve assigned to it.

Conclusion

So, that’s it, I have a SvelteKit app with Lucia auth and Turso deployed on Fly.io with a domain assigned to it.

Now I have to build out the app, but that’s for another post! 😅