39 lines
1.6 KiB
Markdown
39 lines
1.6 KiB
Markdown
|
---
|
||
|
|
date: 2025-07-03
|
||
|
|
title: Imperative or declarative
|
||
|
|
permalink: /daily/2025/07/03/imperative-or-declarative
|
||
|
|
---
|
||
|
|
|
||
|
|
Yesterday, I wrote about [infrastructure as code][0] and mentioned some of the IaC tools that are available.
|
||
|
|
|
||
|
|
I use Terraform to manage the DNS records for my websites, and use NixOS to configure my laptops and home server.
|
||
|
|
|
||
|
|
Before NixOS, I used Ansible to provision servers and [deploy application code][1].
|
||
|
|
|
||
|
|
Ansible is imperative, which means you need to declare each step that needs to be run.
|
||
|
|
|
||
|
|
You need to say to install a package, like a web server.
|
||
|
|
|
||
|
|
You need to say to create any required users or groups.
|
||
|
|
|
||
|
|
You need to configure the service so it starts when the server boots.
|
||
|
|
|
||
|
|
You need to create the configuration files and symlink or copy them to the correct path.
|
||
|
|
|
||
|
|
You need to add as many steps as needed to perform the task, that will be executed in the given order.
|
||
|
|
|
||
|
|
## Declarative configuration
|
||
|
|
|
||
|
|
This makes sense for application deployments, but for server configuration, you can also use declarative tools like Terraform and NixOS.
|
||
|
|
|
||
|
|
Instead of writing each step, you declare what the final desired state is.
|
||
|
|
|
||
|
|
You say Nginx should be enabled by writing `services.nginx.enable = true;` or declaring what the configuration file contents should be - not how to create or symlink the file.
|
||
|
|
|
||
|
|
This also makes the underlying code easier to update or refactor.
|
||
|
|
|
||
|
|
If how you install or configure a program changes, you don't need to update your infrastructure code as the final state will be the same - regardless of how it's done.
|
||
|
|
|
||
|
|
[0]: /daily/2025/07/02/what-infrastructure-code
|
||
|
|
[1]: /presentations/deploying-php-ansible-ansistrano
|