How can I avoid heroku stopping my dyno?

Heroku now has a cron-equivalent add-on called Scheduler. Based on a tutorial:

1. In app/lib/tasks, add a file named scheduler.rake with this task defined:

   desc "This task is called by the Heroku cron add-on"
   task :call_page => :environment do
      uri = URI.parse('http://www.myapp.org/')
      Net::HTTP.get(uri)
   end
   

2. Add the "Scheduler" addon from your Heroku control panel or from the console:

   heroku addons:add scheduler:standard

3. Configure Scheduler to run this task hourly.

   heroku addons:open scheduler

I suspect this is Heroku's preferred method, as a Heroku community rep demonstrated this technique at a talk.

Simple answer: You pay for it.

Ramp up to two dynos and your app will not idle.

If cost conscious then only ramp up to two web dynos for short periods of time around your client's demos. Heroku only charge $0.05 per hour.

Or drive frequent traffic to the app somehow so it does not idle. But Heroku offer such a great service that you use for free so why not throw them a few cents for the periods you need guaranteed response.

You can point a Pingdom check at your site's URL. As a bonus, you'll be keeping an eye on downtime while you do so.

Using the New Relic monitoring service seems to be a good option...

How to in the following post:

Avoid Heroku idling with New Relic pings

It's in the FAQ, at the end, "What is dyno idling?"

https://devcenter.heroku.com/articles/dynos

Apps that have more than 1 web dyno are never idled out. Workers dynos are never idled out.

Basically, this happens on the free tier. If you start up a second dyno (i.e., pay $35/month), the dynos will not idle.

If it's the case where your client is doing a presentation, i.e., a scheduled look at the application during a meeting, the idling doesn't occur until after an hour of inactivity. If he doesn't feel like paying $35/month in this scenario, he can poke the application before the meeting to wake it up.

There are two options:

1. Pay for it

   As soon as you heroku scale web= above 1 the app will never iddle out, as cjk and flurdy also mention in their answer. This is by far the best option if you have a single site that is paying its own bills. If you're maintaining many sites, the costs add up though.

2. Periodically ping the service

   This option is the interesting one. For low trafic sites there is no free solution I could find. Pingdom (as mentioned by ceejayoz) is free for one site, so that would solve the problem once. If you need more sites, you can also use Iron.io to keep your heroku dynos alive. This will also quickly run out of the free tier though and then you'll be paying Iron.io.

   If you are lucky enough to have a server running already, you can stick a curl to your site in the crontab. This solution scales best of course.

Have your Heroku-hosted site indexed by Google (and other major search engines).

A Heroku app I uploaded a few months ago for internal use, but which has to be accessible to clients, has somehow been found by Google and the (very small) public section of the site indexed. Nevertheless, a few months after first putting it up, Google is making about one request every 70 seconds, more than enough to keep the dyno active continuously.