Heroku example for the Deployment Guide (#235)

guides/deployment/readme.md

@@ -26,7 +26,7 @@ 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
@@ -50,7 +50,7 @@ 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
@@ -63,6 +63,51 @@ 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:
+
+~~~ bash
+# Procfile
+
+web: bundle exec falcon host
+~~~
+
+~~~ ruby
+# 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
+~~~
+
+~~~ ruby
+# preload.rb
+
+require_relative "config/environment"
+~~~
+
 ## Falcon Virtual
 
 Falcon can replace Nginx as a virtual server for Ruby applications.