How to click on Heroku without dropping the application

Question

It’s just interesting how everyone pushes updates to their production server on Heroku, without reaching the application for a few seconds?

Clicking on Heroku (especially using something like Unicorn) takes some time to load the web application. Especially when end users try to access the site. They end in 503 pages. Unicorn processes take up to 30 seconds to a minute to load.

Answer 1

This requires TWO, and this is not trivial.

1) Migrations must be backward compatible (i.e., performed while the application is active). See this article about this: http://pedro.herokuapp.com/past/2011/7/13/rails_migrations_with_no_downtime/

2) Deployment using two heroku applications. I opened a ticket with Heroku on this topic, and that was their answer:

We are currently working on a solution that provides zero downtime but does not have an ETA when it may be available.

In the meantime, a workaround that might be possible is to deploy to two separate applications. You can click the new code on the second application, unscrew it, then move the domain names to the second application. Wash and repeat the next time you deploy. This is less than ideal, but may have the desired result in the interim.

If you do this, you will want to automate as much as possible, as there are many ways to ruin this. Here is an article on this topic: http://casperfabricius.com/site/2009/09/20/manage-and-rollback-heroku-deployments-capistrano-style/

Why?

Both of these solutions should be implemented , because database migration should work in BOTH code versions (live and to-be-live). Once you get started, THEN you can solve the second problem when the application does not seem to have come down. There is no supported way to turn and rotate individual speakers after triggering a click.

UPDATE: Now with Heroku there is a beta function. To use, follow these steps before clicking:

heroku labs:enable -a APP_NAME preboot

This will change the behavior of the application during click. He will push a parallel instance, which will warm up for two minutes. Almost exactly two minutes after clicking, all traffic will go to a new application. Be careful with migrations, as I mentioned above, as they still remain a problem.

Answer 2

Heroku is currently testing its new preload feature in beta. You can check it out. Unfortunately, it only works for ≥2 web speakers. And that also does not work for heroku scale web=… , which would be important to get it to work with HireFireApp.com.

Answer 3

You should take a look at this article:

http://rhnh.net/2011/05/28/speeding-up-rails-startup-time