Heroku Cedar: How to scale WEB dynos based on time of day - ruby-on-rails-3

Question

I want my Rails 3.1 app to scale up to 1 web dyno at 8am, then down to 0 web dynos at 5pm.
BUT, I do not want to sign up for a paid service, and I cannot count on my home computer being connected to the internet.
It seems like the Heroku Scheduler should make this trivial. Any quick solutions or links?

Answer 1

The answer is 'yes' you can do this from scheduler and it's trivial once you know the answer:
Add a heroku config var with your app name: heroku config:add APP_NAME:blah
Add gem 'heroku' to your Gemfile
In order to verify, manually scale up/down your app: heroku ps:scale web=2
Add a rake task to lib/tasks/scheduler.rake:
desc "Scale up dynos"
task :spin_up => :environment do
heroku = Heroku::Client.new('USERNAME', 'PASSWORD')
heroku.ps_scale(ENV['APP_NAME'], :type=>'web', :qty=>2)
end
# Add a similar task to Spin down
Add the Scheduler addon: heroku addons:add scheduler:standard
Use the Scheduler web interface to add "rake spin_up" at whatever time you like
Add a rake spin_down task and schedule it for whenever.
Notes:
Step 1 is needed because I couldn't find any other way to be certain of the App name (and I use 'staging' and 'production' environments for my apps.
Step 3 is required because otherwise the ruby command errors out as it requires that you first agree (via Yes/No response) that you will be charged money as a result of this action.
In step 4, I couldn't find any docs about how to do this with an API key via the heroku gem, so it looks like user/pass is required.
Hope this helps someone else!

Answer 2

Just implemented this approach (good answer above #dnszero), thought I would update the answer with Heroku's new API.
Add your app name as a heroku config variable
require 'heroku-api'
desc "Scale UP dynos"
task :spin_up => :environment do
heroku = Heroku::API.new(:api_key => 'YOUR_ACCOUNT_API_KEY')
heroku.post_ps_scale(ENV['APP_NAME'], 'web', 2)
end
This is with heroku (2.31.2), heroku-api (0.3.5)

Answer 3

You can scale your web process to zero by
heroku ps:scale web=0
or back to 1 via
heroku ps:scale web=1
you'd then have to have a task set to run at 8 that scales it up and one that runs at 17 that scales it down. Heroku may require you to verify your account (ie enter credit card details) to use the Heroku Scheduler plus then you'd have to have the Heroku gem inside your app and your Heroku credentials too so it can turn your app on or off.
But like Neil says - you get 750hrs a month free which can't roll over into the next month so why not just leave it running all the time?

Answer 4

See also this complete gist, which also deals with the right command to use from the Heroku scheduler: https://gist.github.com/maggix/8676595

Answer 5

So I decided to implement this in 2017 and saw that the Heroku gem used by the accepted answer has been deprecated in favor of the 'platform-api' gem. I just thought I'd post what worked for me, since i haven't seen any other posts with a more up-to-date answer.
Here is my rake file that scales my web dynos to a count of 2. I used 'httparty' gem to make a PATCH request with appropriate headers to the Platform API, as per their docs, in the "Formation" section.
require 'platform-api'
require 'httparty'
desc "Scale UP dynos"
task :scale_up => :environment do
headers = {
"Authorization" => "Bearer #{ENV['HEROKU_API_KEY']}",
"Content-Type" => "application/json",
"Accept" => "application/vnd.heroku+json; version=3"
}
params = {
:quantity => 2,
:size => "standard-1X"
}
response = HTTParty.patch("https://api.heroku.com/apps/#{ENV['APP_NAME']}/formation/web", body: params.to_json, headers: headers)
puts response
end

Answer 6

As an update to #Ren's answer, Heroku's Platform API gem makes this really easy.
heroku = PlatformAPI.connect_oauth(<HEROKU PLATFORM API KEY>)
heroku.formation.batch_update(<HEROKU APP NAME>, {"updates" =>
[{"process" => <PROCESS NAME>,
"quantity" => <QUANTITY AS INTEGER>,
"size" => <DYNO SIZE>}]
})

Answer 7

If you're running on the cedar stack, you won't be able to scale to zero web dynos without changing the procfile and deploying.
Also, why bother if you get one free dyno a month (750 dyno hours, a little over a month in fact)?