Fly.io

Fly.io supports WebSockets and provides automatic HTTPS—a good fit for PyView apps.

Prerequisites

Create a Fly.io account
Install the Fly CLI:

# macOS
brew install flyctl

# Linux
curl -L https://fly.io/install.sh | sh

fly auth login

Initial Setup

From your project directory:

fly launch

This creates a fly.toml configuration file. When prompted:

Choose a unique app name (or accept the generated one)
Select a region close to your users
Skip database setup unless you need it

Configuration

Here’s a complete fly.toml for a PyView app:

app = "your-app-name"
primary_region = "ewr"  # Change to your preferred region

[build]
  # Uses Dockerfile in the current directory

[env]
  # Non-secret environment variables
  PORT = "8000"

[http_service]
  internal_port = 8000
  force_https = true
  auto_stop_machines = false  # Keep alive for WebSocket connections
  auto_start_machines = true
  min_machines_running = 1

  [http_service.concurrency]
    type = "connections"
    hard_limit = 100
    soft_limit = 50

[[vm]]
  size = "shared-cpu-1x"
  memory = "256mb"

Key settings:

force_https = true — Redirects HTTP to HTTPS (recommended)
auto_stop_machines = false — Keeps machines running for WebSocket connections
internal_port = 8000 — Matches uvicorn’s default port

Setting Secrets

fly secrets set PYVIEW_SECRET="$(openssl rand -base64 32)"

Secrets are encrypted and injected as environment variables. List them with:

fly secrets list

Deploying

fly deploy

Fly builds your Docker image remotely and deploys it. Once deployed:

fly open

Monitoring

View logs in real-time:

fly logs

Check app status:

fly status

SSH into a running machine for debugging:

fly ssh console

Scaling

Regions

fly regions add lax ord  # Los Angeles, Chicago

Machine Size

fly scale vm shared-cpu-2x --memory 512

Or update fly.toml:

[[vm]]
  size = "shared-cpu-2x"
  memory = "512mb"

Multiple Machines

fly scale count 2

Fly’s load balancer uses sticky sessions by default, which works well with PyView’s WebSocket connections.

Custom Domain

fly certs add your-domain.com

Follow the DNS instructions provided. Fly handles TLS certificates automatically.

Troubleshooting

App won’t start

Check the logs:

fly logs

Common issues:

Missing PYVIEW_SECRET — Set it with fly secrets set
Wrong port — Ensure internal_port matches your uvicorn port
Build failures — Check Dockerfile syntax

WebSocket not connecting

Verify HTTPS is working (WebSocket requires secure connection in production)
Check that auto_stop_machines = false if using aggressive auto-stop

Slow cold starts

If your app stops and restarts frequently:

[http_service]
  auto_stop_machines = false
  min_machines_running = 1

Example: PyView Demo

The PyView examples run on Fly.io. See the fly.toml in the repository for a working configuration.