Primcloud
Docs menu

Moving an app from Fly.io

A walkthrough for moving a running Fly.io app to Primcloud with zero downtime.

On this page

Before you start#

You'll need a Primcloud account with GitHub connected (the Quickstart walks you through it) and flyctl, so you can read your secrets.

A few things go by different names here:

On Fly.io On Primcloud
Process group in [processes] Pod formation
Machine count Instances
VM size Compute size
fly secrets Secrets
fly ssh console -C Tasks
*.fly.dev *.primcloud.app

The guide follows one app, hack-the-planet, from start to finish.

1. Turn your fly.toml processes into a Procfile#

Primcloud doesn't read fly.toml. Take its [processes], and the release_command under [deploy] if you have one:

fly.toml 
[deploy]
  release_command = "perl bin/release.pl"

[processes]
  app = "perl bin/board.pl"
  worker = "./bin/queued -d"

[http_service]
  internal_port = 8080
  processes = ["app"]

Each becomes a line of a Procfile at the root of your repo, with release_command as the release line:

Procfile 
release: perl bin/release.pl
web: perl bin/board.pl --port=$PORT
worker: ./bin/queued -d

Only the web line gets HTTP traffic, on the port in $PORT. The group your [http_service] sends traffic to, app here, becomes web, and it binds to $PORT instead of the internal_port.

No [processes] section? Your Machines ran the CMD from your image. Most languages start a sensible web process on their own, and your language's page under Language Support says what it runs. If you need your CMD instead, write it as the web line.

Note

On Standard, the build uses your language's own files and ignores your Dockerfile. Move the packages it installs with apt-get into a project.toml, as the Customizing the build page for your language under Language Support shows. Pro and Team can build from a Dockerfile, as Plans shows.

2. Pull up your secrets#

Terminal 
fly secrets list -a hack-the-planet

Leave PORT out, since Primcloud sets it for you. Fly shows each secret's name but never its value, so get the values from where they came from: your password manager, or the dashboard of the service that issued them. Copy the [env] section of your fly.toml too.

Warning

Don't copy a whole environment dump from a running Machine. Leave out PRIMARY_REGION and every variable starting with FLY_, which Fly sets for the Machine, and PATH, HOME and HOSTNAME, which would override the values your app gets here.

3. Import your repo#

From your applications list, hit Import Git Repository. Pick the repo, then on the Configure step choose your branch and region.

That Configure step also has a Secrets list. Add your secrets there and they're saved before the first build.

The Secrets list with paired key/value rows, one value revealed and the rest masked, per-row remove buttons, Add More, and Save

Check the commit and hit Import. The first deploy starts right away.

A deployment's detail page with its Build and Rollout phases both complete, the Build phase expanded to its log

Once Rollout shows Complete, open your app at hack-the-planet-production.primcloud.app. Forgot a secret? Add it under Settings → Secrets and save. Once your app is running, saving redeploys it with the new value, no rebuild needed. If the first deploy failed, save the secret, then hit Redeploy on that deployment.

Warning

Pods don't keep files between restarts or deploys. If your app writes to a Fly volume, move that data into an object store before you move your domain.

4. Turn your workers on#

Important

After the first deploy, only web is running. Every other process starts at 0 instances, so your workers are off until you scale them up.

Open Pod Formations on your app's dashboard and expand a formation. Instances is your Machine count. Formation Size is your VM size: the memory and CPU each instance gets.

The Pod Formations panel with web expanded at 2 instances on Standard 2x, showing the Formation Size selector and the Instances slider, and worker below it at 1 instance on Standard 1x

Everything starts on Standard 1x, our smallest size. Memory is a hard limit, so pick a size with at least as much memory as your Machines have on Fly. Scaling formations has the details.

5. Swap fly ssh console -C for tasks#

Anything you'd run with fly ssh console -C becomes a task. It runs your command on a fresh instance of your current build, with the same secrets as your app, and streams the output while it runs.

A task run with the command across the top, a succeeded badge with its exit code, and the run's output below

A task isn't an interactive shell. Give it a command and it runs until that command exits.

6. Move your domain#

  1. Add your domain in your app's Settings. We'll show you the two DNS records to add, a CNAME and a TXT record.
  2. Add the TXT record at your DNS provider.
  3. Replace the records that point your domain at Fly, its A and AAAA records or a CNAME to your fly.dev hostname, with the CNAME we showed you. For a root domain like example.com, use an ALIAS, ANAME or flattened CNAME; DNS setup explains why.
  4. Wait for the domain to show Success. We keep checking DNS for up to 72 hours, and once it verifies, your app is served over HTTPS.
  5. Make it your primary domain. Your primcloud.app URL then redirects to it.
A pending custom domain showing its status with the exact CNAME and TXT DNS records to add, each with a copy-to-clipboard button

7. Switch Fly off#

Delete your Fly app:

Terminal 
fly apps destroy hack-the-planet