Procfile

Railpack automatically detects and uses Procfile configuration files to determine how your application should start. This is compatible with Heroku-style Procfiles and provides a simple way to specify different process types for your application.

Note

Procfiles are deprecated and natively setting the start command with RAILPACK_START_CMD or in the railpack.json config file is the recommended

Detection

Railpack will automatically detect a Procfile in your project root directory. No additional configuration is required - if a Procfile exists, Railpack will use it to set the container start command.

Format

The Procfile uses a YAML-style format where each line defines a process type and its associated command:

web: gunicorn --bind 0.0.0.0:3333 main:app
worker: celery worker -A myapp.celery
scheduler: celery beat -A myapp.celery

Process Type Priority

Railpack prioritizes process types in the following order:

1. web - Highest priority, typically used for HTTP servers
2. worker - Second priority, typically used for background job processors
3. Any other process type - If neither web nor worker are defined, Railpack will use the first available process type

This priority system ensures that web servers are preferred for containerized deployments, while still supporting applications that only define worker processes or custom process types like scheduler, urgentWorker, or api.

Examples

Web Application

web: node server.js

Background Worker

worker: python worker.py

Multiple Process Types

web: gunicorn app:application
worker: celery worker -A app.celery
scheduler: celery beat -A app.celery

In this example, Railpack will use the web command as the container start command.

Custom Process Types

api: ./bin/api-server
urgentWorker: python urgent_tasks.py

If no web or worker process types are defined, Railpack will use the first available process type (in this case, api).

Integration with Other Configuration

The Procfile start command can be overridden by:

• Setting RAILPACK_START_CMD environment variable
• Defining deploy.startCommand in your railpack.json config file

The priority order is:

1. RAILPACK_START_CMD environment variable (highest priority)
2. deploy.startCommand in railpack.json
3. Procfile process types (web → worker → other)
4. Provider-specific defaults (lowest priority)