Heroku Scaler

The Heroku Scaler gem allows for free scaling of Heroku web dynos. It exposes 3 simple rake tasks that can be called from the free Heroku Scheduler.

This is perfect for applications that see heavy use during known times of the day or week. For example, we have some customers with business systems that see 99.9% of their traffic during regular business hours on the weekdays. Since Heroku charges for dynos based on the number of seconds the dynos are running, scaling down application dynos during off-peak times can mean big savings. Running your larger dyno setup only during business hours - which is only 25% of the time - can save a bundle! There are other tools that purport to do this but they often charge money and have, in our experience, been poorly supported.

Commands

The Heroku Scaler gem exposes three rake commands when added to a Rails application.

The below command will scale your application web dynos to the SCALE_BIG_DYNO_COUNT and SCALE_BIG_DYNO_TYPE.

rake heroku_scale:web:up

The below command will scale your application web dynos to the SCALE_SMALL_DYNO_COUNT and SCALE_SMALL_DYNO_TYPE.

rake heroku_scale:web:down

The below command will scale your application web dynos to the SCALE_BIG_DYNO_COUNT and SCALE_BIG_DYNO_TYPE if it is a weekday.

rake heroku_scale:web:up_if_weekday

Configuration options

All of these configuration options can be set through the Heroku application configuration (heroku config:set SOME_SETTING=some_value)

Setting	Default
SCALE_APP_NAME		your Heroku application name
SCALE_BIG_DYNO_COUNT	3	the number of scaled up dynos
SCALE_BIG_DYNO_TYPE	Standard-2X	the type of scaled up dyno
SCALE_OAUTH_TOKEN		Heroku account auth token
SCALE_SMALL_DYNO_COUNT	1	the number of scaled down dynos
SCALE_SMALL_DYNO_TYPE	Standard=1X	the type of scaled down dyno

Installation

1. Add Heroku Scaler to your Rails application.

add the gem to your Gemfile

gem "heroku-scaler"

User Bundler to install the gem in your project

bundle

1. Generate an API Key from an appropriate Heroku account ("Manage account" -> "API Key")

2. Add settings to your Heroku configuration.

Assuming a Heroku application named "my-cool-app":

heroku config:set SCALE_APP_NAME=my-cool-app
heroku config:set SCALE_BIG_DYNO_COUNT=3
heroku config:set SCALE_BIG_DYNO_TYPE=Standard-2X
heroku config:set SCALE_OAUTH_TOKEN=heroku_api_key_here
heroku config:set SCALE_SMALL_DYNO_COUNT=1
heroku config:set SCALE_SMALL_DYNO_TYPE=Standard-1X

1. Install the Heroku Scheduler into your Heroku application.

2. Add scheduled events at the times you wish for your application to scale up or down.

Running tests

bundle
bundle exec rspec spec

Left to do

1. Add support for time zones so the heroku_scale:web:up_if_weekday task behaves as expected in all time zones.
2. Add support for scaling Heroku workers

Contributing

Please feel free to submit pull requests or issues. Support for more servers would be neat.

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

About Foraker Labs

Foraker Labs builds exciting web and mobile apps in Boulder, CO. Our work powers a wide variety of businesses with many different needs. We love open source software, and we're proud to contribute where we can. Interested to learn more? Contact us today.

This project is maintained by Foraker Labs. The names and logos of Foraker Labs are fully owned and copyright Foraker Design, LLC.