Software erosion is what happens to your app without your knowledge or consent: it was working at one point, and then doesn't work anymore. When this happens you have to invest energy diagnosing and resolving the problem. Over a year ago Heroku's CTO, Adam Wiggins, first wrote about erosion-resistance on Heroku. Part of erosion-resistance is communication, and knowing what to expect moving into the future. This post will clarify what we mean by erosion-resistance, and help you understand what to expect when one of our features is deprecated or is sunset.
Erosion-resistance means that your apps are protected against accidental or unannounced changes because there is an explicit contract between your app and the platform. Heroku insulates you from erosion by providing a transparent, managed service. We give you early visibility and full details on what's happening with your app, and options for how to respond to any changes. In many cases we can take care of system changes for you automatically, but when we can't, we tell you what your options are, how to proceed, and how much time you have.
To keep your application stable Heroku applies fixes and improvements, such as backwards-compatible updates released by maintainers, to the software on our platform. This protects applications on our platform without interrupting them. Occasionally security patches are introduced to operating systems and sometimes to programming languages. By using the Heroku platform, you can be confident that the underlying software you are using is safe and stable.
If a backwards-incompatible change needs to be applied to our platform we will always communicate the change ahead of time and provide sufficient information so that you can take the necessary steps to fix any incompatibilities. These changes are communicated through our deprecation and sunsetting process.
When Heroku deprecates a product or service, we are actively suggesting that you no longer use that feature. Deprecations may be communicated through notices coming from the Heroku CLI, banners in our Dev Center, or messages on our website. These notices may be accompanied by blog posts, changelog entries, official tweets, or direct emails when appropriate. Deprecation of a product will typically suggest using a more recent, stable, or feature rich product, so you can have the best experience using Heroku. These notices will not affect currently running apps. If, however, only a few applications are using a feature in production, Heroku may choose to sunset the feature.
As a product is sunset, it will be gradually phased out until it can be deactivated or removed from our system. We will only sunset products that have seen significantly decreased usage, and we will not deactivate heavily used features. Any product being sunset will have been deprecated for some time and will begin with an announcement similar to the deprecation but including additional information such as the date of the product's deactivation.
If possible, we will migrate any affected users to a comparable product. A good example of this is the Cron Add-on. Cron was deprecated in April of 2012, and after a majority of its users transitioned away from the product it was sunset. Any users left using Cron were automatically migrated to the superior Scheduler Add-on.
If we sunset a product you are using, and we cannot automatically migrate, there are several things you can expect from Heroku. You will receive communication of the changes along with a plan moving forward. This will include a time-line with enough time to make any changes needed. Our goal is always to provide the best experience, to our developers, and to give the highest level of support possible.
At Heroku, we seek to be the most powerful platform to the largest number of users. By providing a strong contract with our platform, you can be confident using Heroku, and be prepared for when change happens. To stay up to date with our current erosion-resistance policies, you can always check our erosion-resistance documentation on the Dev Center.