Over the past four years, the Heroku Runtime team has transitioned from occasional, manual deployments to continuous, automated deployments. Changes are now rolled out globally within a few hours of merging any change—without any human intervention. It's been an overwhelmingly positive experience for us. This post describes why we decided to make the change, how we did it, and what we learned along the way.

Where We...


As outlined in a previous blog post, Heroku Data services undergo routine maintenances for security and patching. In this post, we describe the process used to minimize downtime for Heroku Postgres and Heroku Redis premium ‘High Availability’ plans and how we optimized the process to perform up to 75% faster.

Data Services Architecture

High availability plans for Postgres and Redis are designed to have two database instances running at the same time. One is a writeable primary database server and the other is a read-only hidden standby. Since the standby is hidden, customers cannot access it during normal operations.

faster-swaps-overview-rev4

Before starting a planned maintenance, we do our best to ensure...


This is the second post in a two-part series about accessibility. The first post shares why designing for accessibility is important to us and why we encourage you to incorporate it into your software design process.

Heroku’s first accessibility initiative was to reach Level AA for luminance contrast ratio as defined by the internationally recognized best practices of the Web Content Accessibility Guidelines (WCAG) 2.0. This ratio guarantees the legibility of text against its background, in order to ensure all users can perceive Heroku’s user interfaces equally.

This benefits people with color-vision deficiencies (like Deuteranopia or Protanopia which affect 7 to 12% of men), age-related...


Every organization needs to be data-driven in order to be successful. Whether you're tracking an application's performance, incoming support tickets, or revenue rates, different components of any company depend on metrics that inform the health of the business.

At Heroku, we're hackers to the core, but that doesn't mean we're all programmers. We build on top of our own platform for everything we do, and one of the products we often use is Heroku Dataclips. If you haven't heard of them before, Heroku Dataclips allow you to create SQL queries in a web GUI that run on your Heroku Postgres database. The unique dataclip URL can then be shared internally or externally,...


For quite some time we've received reports from our larger customers about a mysterious H13 - Connection closed error showing up for Ruby applications. Curiously it only ever happened around the time they were deploying or scaling their dynos. Even more peculiar, it only happened to relatively high scale applications. We couldn't reproduce the behavior on an example app. This is a story about distributed coordination, the TCP API, and how we debugged and fixed a bug in Puma that only shows up at scale.

Screenshot showing H13 errors

Connection closed

First of all, what even is an H13 error? From our error page documentation:

This error is thrown when a process in your web dyno accepts a connection, but then...


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