Using unicorn on Heroku

newrelic_reconnect.rb

# config/initailizers/newrelic_reconnect.rb

# Ensure the agent is started using Unicorn
# This is needed when using Unicorn and preload_app is NOT set to true.
# https://newrelic.com/docs/ruby/no-data-with-unicorn
NewRelic::Agent.after_fork(:force_reconnect => true) if defined? Unicorn

Procfile

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb

unicorn.rb

# config/unicorn.rb

# Minimal Heroku unicorn config
# * I found no real gain from enabling preload_app on Heroku (which makes for faster worker starts/restarts), 
#   and it will cause strange issues if you don't re-establish all connections correctly
# * Heroku has a 30s timeout so we set to 60, allowing them to handle timeouts and issue an H12 error
# * Depending on your memory usage workers can be bumped to 3-4. With Sinatra it can be 8+
worker_processes 3
timeout 60

I've just updated this and increased timeout to >30s timeout, which allows Heroku to handle killing slow workers and issuing an H12. Heroku router errors can be monitored more easily