Beat Heroku's 60 seconds timeout with a proxy.

Heroku will report an application crashing and yield an R10 Boot Timeout error when a web process took longer than 60 seconds to bind to its assigned $PORT. This error is often caused by a process being unable to reach an external resource, such as a database or because Heroku is pretty slow and you have a lot of gems in your Gemfile.

This gem implements a proxy using em-proxy. This proxy is booted almost immediately, binding to the port assigned by Heroku. Heroku now reports the dyno up. The proxy then spawns your application's web server and establishes a connection over a unix domain socket (a file) between the proxy and the application. Once the application is ready, it will be able to serve HTTP requests normally. Until then requests may queue and some may timeout depending on how long it actually takes to start.

Add heroku-forward and em-proxy to your Gemfile. Curently requires HEAD of em-proxy because of this pull request.

gem "heroku-forward", "~> 0.1"
gem "em-proxy", ">= 0.1.8"

Create an application rackup file, eg. my_app.ru that boots your application. Under Rails, this is the file that calls run.

require ::File.expand_path('../config/environment',  __FILE__)
run MyApp::Application

Modify your rackup file as follows. Under Rails this file is called config.ru.

require 'rubygems'
require 'bundler'

$stdout.sync = true
Bundler.require(:rack)

port = (ARGV.first || ENV['PORT'] || 3000).to_i
env = ENV['RACK_ENV'] || 'development'

require 'em-proxy'
require 'logger'
require 'heroku-forward'

application = File.expand_path('../my_app.ru', __FILE__)
backend = Heroku::Forward::Backends::Thin.new(application: application, env: env)
proxy = Heroku::Forward::Proxy::Server.new(backend, { host: '0.0.0.0', port: port })
proxy.logger = Logger.new(STDOUT)
proxy.forward!

This sets up a proxy on the port requested by Heroku and runs your application with Thin.

Heroku Cedar expects a Procfile that defines your application processes.

web: bundle exec ruby config.ru
worker: bundle exec rake jobs:work

You can use foreman to test the proxy locally with foreman start web.

Here's the log output from an application that uses this gem. Notice that Heroku reports the state of web.1 up after just 4 seconds, while the application takes 67 seconds to boot.

2012-12-11T23:33:42+00:00 heroku[web.1]: Starting process with command `bundle exec ruby config.ru`
2012-12-11T23:33:46+00:00 app[web.1]:  INFO -- : Launching Backend ...
2012-12-11T23:33:46+00:00 app[web.1]:  INFO -- : Launching Proxy Server at 0.0.0.0:42017 ...
2012-12-11T23:33:46+00:00 app[web.1]: DEBUG -- : Attempting to connect to /tmp/thin20121211-2-1bfazzx.
2012-12-11T23:33:46+00:00 app[web.1]:  WARN -- : no connection, 10 retries left.
2012-12-11T23:33:46+00:00 heroku[web.1]: State changed from starting to up
2012-12-11T23:34:32+00:00 app[web.1]: >> Thin web server (v1.5.0 codename Knife)
2012-12-11T23:34:32+00:00 app[web.1]: >> Maximum connections set to 1024
2012-12-11T23:34:32+00:00 app[web.1]: >> Listening on /tmp/thin20121211-2-1bfazzx, CTRL+C to stop
2012-12-11T23:34:53+00:00 app[web.1]: DEBUG -- : Attempting to connect to /tmp/thin20121211-2-1bfazzx.
2012-12-11T23:34:53+00:00 app[web.1]: DEBUG -- : Proxy Server ready at 0.0.0.0:42017 (67s).

Heroku::Forward::Proxy::Server.forward! accepts the following options:

• delay: number of seconds to sleep before launching the proxy, eg. proxy.forward!(delay: 15). This prevents queuing of requests or reporting invalid up status to Heroku. It's recommended to set this value to as close as possible to the boot time of your application and less than the Heroku's 60s boot limit.

If you're worried about this implementation, consider building a fail-safe. Modify your config.ru to run without a proxy if DISABLE_FORWARD_PROXY is set as demonstrated in this gist. Add DISABLE_FORWARD_PROXY via heroku config:add DISABLE_FORWARD_PROXY=1.

• Heroku R10 Boot Timeout
• Beating Heroku's 60s Boot Times with the Cedar Stack and a Reverse Proxy by Nicolas Overloop
• Fighting the Unicorns: Becoming a Thin Wizard on Heroku by JGW Maxwell
• eventmachine
• em-proxy

Fork the project. Make your feature addition or bug fix with tests. Send a pull request. Bonus points for topic branches.

MIT License, see LICENSE for details.

(c) 2012 Daniel Doubrovkine, Art.sy