brentjanderson
Zero downtime Postgres upgrades | Knock
We recently performed a zero downtime Postgres upgrade at Knock. This blog post goes into details about the Postgres considerations, although the BEAM & Elixir ecosystem were invaluable in managing the cutover process.
Some Elixir-related bits:
- We used
DynamicSupervisorto start/stop Oban during the cutover. Without going into too much detail, Oban needs aNotifierto coordinate global state, and we rely on the default Postgres notifier (Although there is a new PubSub notifier that we have our eyes on). This Notifier establishes a persistent Postgres connection that is managed outside of your Ecto Repo, and the easiest way to move Oban over to the new instance was to stop and restart it with a new configuration usingDynamicSupervisor - Metaprogramming made it easier to build facade interfaces to our Ecto Repos so that database requests could be routed to the old or new database instance, based on the state of a launch darkly flag. Internally, LD uses ETS and a persistent websocket connection, which helps lookups be fast and up to date. ETS is still not quite fast enough for the volume of DB queries in our system, and so we also used
:persistent_termto set the flag that determined what state we were in during the cutover process. Benchee helped us verify that we weren’t going to have a performance regression. - We looked at Ecto Repo’s
get_dynamic_repofunction, but determined that using a facade was a better fit for our use case. It’s worth knowing what’s available, though, since Ecto comes with a lot of extensibility out of the box. - The concurrency model of the BEAM makes it so much easier to reason about all of the stuff involved in a migration like this. Although you can take a similar approach with most languages, the BEAM didn’t get in the way of reasoning through the specifics of the cutover, especially around how we maintain uptime and data consistency during a cutover like this.
We may do a full post on the BEAM-related details of this upgrade in the future.
Popular Backend topics
Interested in a blazingly fast type checker with 25 years of investment, delivered on the BEAM? Check out Caramel, an exciting project fr...
New
Idioms for the D Programming Language
This thread was posted by one of our members via one of our news source trackers.
New
The run-time speed and memory usage of programs written in Rust should about the same as of programs written in C, but overall programmin...
New
Once a year, I look back at the recent developments in the PHP world, and also look forward to what’s to come. And just like in 2020 and ...
New
Functional programming is an increasing popular programming paradigm with many languages building or already supporting it. Go already su...
New
Tej Pochiraju joins the mix to discuss Progressive Web Apps and how you can support them using Elixir and Phoenix to control IoT devices....
New
Ruby’s Struct is one of several powerful core classes which is often overlooked and under utilized compared to the more popular Hash clas...
New
Hi there!
Recently I was playing around with extracting and updating data in the DB and for fun challenged myself to try to implement a ...
New
In this blog post over on Fly.io I take a look at PHP 8.1’s new Enum class, and show you how it can be used to set up a level structure f...
New
The Ruby ecosystem is rich with tools that make us developers more productive at what we do. Both Rails and Sinatra have been used to bui...
New
Other popular topics
Algorithms and data structures are much more than abstract concepts. Mastering them enables you to write code that runs faster and more e...
New
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
New
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
New
Do the test and post your score :nerd_face:
:keyboard:
If possible, please add info such as the keyboard you’re using, the layout (Qw...
New
Tailwind CSS is an exciting new CSS framework that allows you to design your site by composing simple utility classes to create complex e...
New
If you are experiencing Rails console using 100% CPU on your dev machine, then updating your development and test gems might fix the issu...
New
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
Think Again 50% Off Sale »
The theme of this sale is new perspectives on familiar topics.
Enter coupon code ThinkAgain2021 at checkout t...
New
New
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /svelte
- /onivim
- /typescript
- /kotlin
- /crystal
- /c-plus-plus
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /flutter
- /vscode
- /ash
- /html
- /opensuse
- /zig
- /deepseek
- /centos
- /php
- /scala
- /react-native
- /lisp
- /sublime-text
- /textmate
- /debian
- /nixos
- /agda
- /django
- /kubuntu
- /deno
- /arch-linux
- /nodejs
- /revery
- /ubuntu
- /manjaro
- /spring
- /diversity
- /lua
- /julia
- /markdown
- /c








