79 lines
4.4 KiB
Markdown
79 lines
4.4 KiB
Markdown
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---
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title: "Declaratively Deploying Multiple Blog Versions with NixOS and Flakes"
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date: 2021-10-23T18:01:31-07:00
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expirydate: 2021-10-23T18:01:31-07:00
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draft: true
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tags: ["Hugo", "Nix"]
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---
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### Prologue
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You can skip this section if you'd like.
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For the last few days, I've been stuck inside of my room due to some kind of cold or flu, which
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or
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{{< sidenote "right" "pcr-note" "may or may not be COVID™." >}}
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The results of the PCR test are pending at the time of writing.
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{{< /sidenote >}}
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In seeming correspondence with the progression of my cold, a thought occured in the back of my mind:
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"_Your blog deployment is kind of a mess_". On the first day, when I felt only a small tingling in
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my throat, I waved that thought away pretty easily. On the second day, feeling unwell and staying
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in bed, I couldn't help but start to look up Nix documentation. And finally, on the third day,
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between coughing fits and overconsumption of oral analgesic, I got to work.
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In short, this post is the closest thing I've written to a fever dream.
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### The Constraints
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I run several versions of this site. The first is, of course, the "production" version, hosted
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at the time of writing on `danilafe.com` and containing the articles that I would like to share
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with the world. The second is a version of this site on which drafts are displayed - this
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way, I can share posts with my friends before they are published, get feedback, and even just
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re-read what I wrote from any device that has an internet connection. The third is the Russian
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version of my blog. It's rather empty, because translation is hard work, so it only exists
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so far as another "draft" website.
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My build process (a derivative of what I describe in [rendering mathematics on the back end]({{< relref "./backend_math_rendering.md" >}})) is also fairly unconventional. When I developed this site, the best
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form of server-side mathematics rendering was handlded by KaTeX, and required some additional
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work to get rolling (specifically, I needed to write code to replace sections of LaTeX on
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a page with their HTML and MathML versions). There may be a better way now, but I haven't yet
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performed any kind of migration.
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Currently, only my main site is behind HTTPS. However, I would like for it to be possible to
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adjust this, and possibly even switch my hosts without changing any of the code that actually
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builds my blog.
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### Why Flakes
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This article is about using Nix Flakes to manage my configuration. But what is it that made
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me use flakes? Well, two things:
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* __Adding custom packages__. The Nix code for my blog provides a package / derivation for each
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version of my website, and I want to use these packages in my `configuration.nix` so that
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I can point various Nginx virtual hosts to each of them. This is typically done using
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overlays, but I need a clean way to let my system configuration pull in my blog overlay (or blog
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packages); flakes solve this issue my letting me specify a blog flake, and pull it in as one
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of the inputs.
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* __Versioning__. My process for deploying new versions of the site prior to flakes boiled down to fetcing
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the latest commit from the `master` branch of my blog repository, and updating the `default.nix`
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file with that commit. This way, I could reliably fetch the version of my site that
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I want published. Flakes do the same thing: the `flake.lock` file
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contains the hashes of the Git-based dependencies of a flake, and thus prevents builds from
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accidentally pulling in something else. However, unlike my approach, which relies on custom
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scripts and extra tools such as `jq`, the locking mechanism used by flakes is provided with
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standard Nix tooling. Using Flakes also guarantees that my build process won't break with
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updates to Hugo or Ruby, since the `nixpkgs` version is stored in `flake.lock`, too.
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### The Final Result
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Here's the relevant section of my configuration:
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{{< codelines "Nix" "server-config/configuration.nix" 42 59 >}}
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I really like how this turned out for three reasons. First,
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it's very clear from the configuration what I want from my server:
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three virtual hosts, one with HTTPS, one with drafts, and one with drafts and
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_in Russian_. Second, there's plenty of code reuse. I'm using two builder functions,
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`english` and `russian`, but under the hood, the exact same code is being
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used to run Hugo and all the necessay post-processing. Finally, all of this can be
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used pretty much immediately given my blog flake, which reduces the amount of glue
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code I have to write.
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