Deployment

Falcon Serve

falcon serve is not designed for deployment because the command line interface is not guaranteed to be stable nor does it expose every possible configuration option.

Falcon Hosts

falcon host is designed for deployment, and is the recommended way to deploy Falcon in production. It exposes a well defined interface for configuring services (web applications, job servers, etc).

Configuration

falcon host loads configuration from the falcon.rb file in your application directory. This file contains configuration blocks which define how to host the application and any related services. This file should generally be executable and it invokes falcon host which starts all defined services.

Here is a basic example which hosts a rack application using :

#!/usr/bin/env falcon-host
# frozen_string_literal: true

load :rack, :supervisor

hostname = File.basename(__dir__)
service hostname do
	include Falcon::Environment::Rack
	include Falcon::Environment::LetsEncryptTLS

	# Insert an in-memory cache in front of the application (using async-http-cache).
	cache true
end

service "supervisor" do
	include Falcon::Environment::Supervisor
end

These configuration blocks are evaluated using async-service.

Application Configuration

The environment configuration is defined in the Falcon::Environment module. The module Falcon::Environment::Application environment supports the generic virtual host functionality, but you can customise any parts of the configuration, e.g. to bind a production host to localhost:3000 using plaintext HTTP/2:

#!/usr/bin/env falcon-host
# frozen_string_literal: true

load :rack, :supervisor

hostname = File.basename(__dir__)
service hostname do
	include Falcon::Environment::Rack
	include Falcon::Environment::LetsEncryptTLS

	endpoint do
		Async::HTTP::Endpoint.parse('http://localhost:3000').with(protocol: Async::HTTP::Protocol::HTTP2)
	end
end

service "supervisor" do
	include Falcon::Environment::Supervisor
end

You can verify this is working using nghttp -v http://localhost:3000.

Application Configuration Example for Heroku

Building on the examples above, the following is a full configuration example for Heroku:

# Procfile

web: bundle exec falcon host

# falcon.rb

#!/usr/bin/env -S falcon host

load :rack

hostname = File.basename(__dir__)
port = ENV["PORT"] || 3000

service hostname do
	include Falcon::Environment::Rack

	# By default, Falcon uses Etc.nprocessors to set the count, which is likely incorrect on shared hosts like Heroku.
	# Review the following for guidance about how to find the right value for your app:
	# https://help.heroku.com/88G3XLA6/what-is-an-acceptable-amount-of-dyno-load
	# https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server#workers
	count ENV.fetch("WEB_CONCURRENCY", 1).to_i

	# If using count > 1 you may want to preload your app to reduce memory usage and increase performance:
	preload "preload.rb"

	# Heroku only supports HTTP/1.1 at the time of this writing. Review the following for possible updates in the future:
	# https://devcenter.heroku.com/articles/http-routing#http-versions-supported
	# https://github.com/heroku/roadmap/issues/34
	endpoint Async::HTTP::Endpoint.parse("http://0.0.0.0:#{port}").with(protocol: Async::HTTP::Protocol::HTTP11)
end

# preload.rb

require_relative "config/environment"

Falcon Virtual

Falcon can replace Nginx as a virtual server for Ruby applications.

You need to create a falcon.rb configuration in the root of your applications, and start the virtual host:

$ cat /srv/http/example.com/falcon.rb
#!/usr/bin/env -S falcon host

load :rack, :lets_encrypt_tls, :supervisor

rack 'hello.localhost', :lets_encrypt_tls

supervisor

$ falcon virtual /srv/http/example.com/falcon.rb

The Falcon virtual server is hard coded to redirect http traffic to https, and will serve each application using an internal SNI-based proxy.