Flynn

Apps

Creating Apps

flynn create my-app

This creates a Flynn app and adds a flynn git remote to your repo.

To specify a custom remote name:

flynn create my-app --remote production

Deployment

Git Push

The standard deployment method:

git push flynn master

Flynn uses Heroku buildpacks to detect and build your application. Supported languages include Go, Node.js, Python, Ruby, Java, and PHP.

Custom Buildpacks

Specify a custom buildpack via .buildpacks file or environment variable:

flynn env set BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-nodejs

Or create a .buildpacks file for multi-buildpack support:

https://github.com/heroku/heroku-buildpack-nodejs
https://github.com/heroku/heroku-buildpack-ruby

Zero-Downtime Deploys

Flynn performs rolling deployments by default:

  1. New processes are started
  2. Health checks pass
  3. Old processes are gracefully stopped
  4. Traffic is shifted to new processes

Deploy Timeout

If a deploy is taking too long, cancel it:

flynn deployment cancel

Git Branches

Only pushes to master trigger a deployment. To deploy a different branch:

git push flynn my-branch:master

Configuration

Environment Variables

# Set variables
flynn env set KEY=value ANOTHER=value2

# Get a specific variable
flynn env get KEY

# Unset a variable
flynn env unset KEY

# List all variables
flynn env

External Databases

To use an external database instead of Flynn’s built-in appliances, set the appropriate environment variable:

flynn env set DATABASE_URL=postgres://user:pass@external-host:5432/mydb

Process Types

Define process types in a Procfile:

web: ./server --port $PORT
worker: ./worker
scheduler: ./cron

The web process type is special — it receives HTTP traffic via the router. Other process types run as background workers.

Scaling

# View current scale
flynn scale

# Scale processes
flynn scale web=4 worker=2

# Scale to zero
flynn scale worker=0

Resource Limits

Each process runs in a cgroup with resource limits. Default memory limit is 1 GiB per process.

Domains and Routing

# List routes
flynn route

# Add HTTP route
flynn route add http app.example.com

# Add HTTPS route (with Let's Encrypt or custom cert)
flynn route add http --certificate /path/to/cert.pem --key /path/to/key.pem app.example.com

# Remove route
flynn route remove <ROUTE_ID>

App Management

# List all apps
flynn apps

# Delete an app
flynn delete --yes

# View app info
flynn info