Provide an example falcon.rb setup for Rails (migrating from Puma) about falcon

[trevorturk]

I left some related notes here for others that might be looking: #121

My current setup for a Rails app running on Heroku looks like this:

Procfile:

web: bundle exec ./falcon.rb

falcon.rb

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

load :rack

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

rack hostname do
  append preload "preload.rb"
  cache false
  count ENV.fetch("FALCON_COUNT", 1).to_i
  endpoint Async::HTTP::Endpoint.parse("http://0.0.0.0:#{port}").with(protocol: Async::HTTP::Protocol::HTTP11)
end

preload.rb

require_relative "config/environment"

...this doesn't cover all of the options in that example Puma config, but it might be a start if someone is migrating from Puma to Falcon, I'm sure a PR with documentation/guide content would be most welcome!

[ioquatix]

This will be fixed in Rails 7.1

Rails 7.0 is incompatible.

[joeldrapper]

I followed the current Rails guide on a brand new Rails install and immediately ran into this error.

               | Task may have ended with unhandled exception.
               |   Concurrent::IllegalOperationError: Cannot release a read lock which is not held
               |   → /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/concurrent-ruby-1.2.2/lib/concurrent-ruby/concurrent/atomic/reentrant_read_write_lock.rb:246 in `release_read_lock'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/actionview-7.0.4.3/lib/action_view/cache_expiry.rb:21 in `complete'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/execution_wrapper.rb:37 in `before'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:423 in `block in make_lambda'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:199 in `block (2 levels) in halting'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:687 in `block (2 levels) in default_terminator'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:686 in `catch'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:686 in `block in default_terminator'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:200 in `block in halting'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:595 in `block in invoke_before'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:595 in `each'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:595 in `invoke_before'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/callbacks.rb:106 in `run_callbacks'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/execution_wrapper.rb:143 in `complete'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/activesupport-7.0.4.3/lib/active_support/execution_wrapper.rb:137 in `complete!'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/actionpack-7.0.4.3/lib/action_dispatch/middleware/executor.rb:15 in `block in call'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/rack-2.2.6.4/lib/rack/body_proxy.rb:29 in `close'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/protocol-rack-0.2.4/lib/protocol/rack/body/enumerable.rb:58 in `close'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/protocol-http-0.24.1/lib/protocol/http/body/wrapper.rb:32 in `close'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/protocol-http-0.24.1/lib/protocol/http/body/deflate.rb:36 in `close'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/async-http-0.60.1/lib/async/http/protocol/http2/output.rb:109 in `passthrough'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/async-2.5.0/lib/async/task.rb:158 in `block in run'
               |     /Users/joeldrapper/.rbenv/versions/3.2.1/lib/ruby/gems/3.2.0/gems/async-2.5.0/lib/async/task.rb:310 in `block in schedule'