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Learning Lektor

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I've spent the last few days learning how to use Lektor, a static content management system written in Python a hybrid between a CMS (like Wordpress or Drupal) and a static website generator (like Jekyll or Pelican). I like Lektor a lot -- so much so that I re-wrote this website from scratch using Lektor! The code behind this site is public on GitHub, if you're curious. Since I just learned a ton about it in a very short amount of time, I think it's fitting that my first blog post should be about it.

What is Lektor?

Lektor is a "static content management system". What does that mean, exactly? It's basically a hybrid between a content management system (like Wordpress or Drupal) and a static website generator (like Jekyll or Pelican).

Content management systems (CMS) are great because they are easy to modify. An editor can visit an admin page, click a few buttons, type into a few text fields, and poof: more content has been added to the website. Non-technical users don't need to edit computer code, they can use a more friendly and familiar interface. The downside is, CMS websites usually require complex infrastructure (databases, search indexes, multiple webservers, etc) which is difficult and expensive to maintain. In addition, CMS websites often have performance problems on production, especially when they become popular. Caching can mitigate these performance problems, but caching has its own complexities. Suffice it to say that running a popular CMS website on production is very, very difficult.

Static websites are great because they are simple and easy to run on production. A static website consists of files that are uploaded to a web server and served directly from disk, without going through any sort of backend programming language like Python or PHP. These files can be HTML, CSS, JavaScript, images, or anything else that a web browser might need to display a beautiful, functional website. Because these files are served directly from disk, static websites are dramatically more performant than CMS websites, which in turn makes them dramatically cheaper to run. The downside is that editing static websites is difficult, especially for non-technical editors. Using a static website generator like Jekyll makes it easier, because you can use a templating system to separate content from presentation and write content using languages like Markdown, which are much easier to write than HTML. However, many non-technical users aren't comfortable editing text files or deploying files to a web server. As a result, finding people to write and edit content for a static website is very, very difficult.

Lektor is a static website generator with an integrated CMS. Lektor produces static websites that can be run on production easily and cheaply. However, Lektor also has an integrated admin page where editors can click buttons and type in text fields in order to create and edit content. Lektor doesn't use a database like a traditional CMS; instead, it stores content in files on disk, and when editors create and edit content through the admin page, Lektor saves those changes to those content files. It's the best of both worlds! You can even maintain your website using a content management system like Git, since all the information is saved in text files.

Lektor and Python 3

Lektor was created by Armin Ronacher, a very prolific developer in the Python community. Armin has a complex view of Python 3, but my understanding is that he generally views Python 3 as a mistake. Perhaps as a result of this, Lektor is not currently compatible with Python 3 -- an issue that struck me right away when I tried to install and use it, and got an error.

Fortunately, porting to Python 3 is finicky but not difficult, so I made a pull request to port Lektor to Python 3. That pull request has attracted a fair amount of attention: apparently a lot of other people also want to see Lektor run on Python 3! The pull request is currently waiting for review, and I'm hoping that it will be reviewed and merged soon.

Using Lektor

The first thing I had to wrap my head around when using Lektor is the "database" system that it uses. Rather than using a traditional database like PostgreSQL or MySQL, Lektor saves data in text files on disk, and can run queries over these files. Although it's unfamiliar, it ends up working quite well.

Every page in your Lektor-powered site requires three files: a model file, a content file, and a template file. However, many pages will share the same model file and template file, and only the content files are unique to each page. In a traditional CMS, the model file is like the database table, while the content file is like the row or rows in the database that correspond to content in the page. Template files are used to render content into HTML, the same way they're used in a traditional CMS.

For example, this page you are viewing right now uses the models/blog-post.ini model file, the content/blog/learning-lektor/contents.lr content file, and the templates/blog-post.html template. Lektor mixes them all together to produce the HTML page you see in front of you: the text of the blog post comes from the content file, the Markdown formatting happens because the model file says that the content file is in Markdown format, and the template displays the rendered Markdown along with the title, sidebar, and everything else on the page.

Once I understood how these three pieces fit together, I was able to speed through very quickly, creating models, content, and templates that worked together cleanly. I occasionally checked out the admin page and tweaked its layout using the model files, but mostly I worked with Lektor's text files directly, since I'm very comfortable with plain text.

Lektor Plugins

Like most of Armin Ronacher's work, Lektor is designed to be extensible -- and in fact, just about any website you build with Lektor will need at least one or two plugins to make it do what you want. I found the plugin system to be very well designed, with only one or two problems so far.

I'm using the official webpack-support plugin to handle asset management for my site. Webpack is written in Node.js, and it does way more things than I'll ever understand. Primarily, though, it bundles multiple JavaScript files into one, resolving dependencies along the way using CommonJS or AMD. It also does the same sort of bundling for CSS files, and can compile Sass along the way. It produces source maps, dynamically recompiles files when they change, handles custom font files with ease, and for all I know there's probably a way to make it cook you dinner and perform backflips as well. Fortunately, the webpack-support plugin for Lektor has some good documentation for how to get up and running with a basic configuration, which was all I needed.

I also spent a lot of time learning how to write my own plugin, since I wanted to display a table of contents for my tutorials, and the Markdown tools that Lektor uses can't produce a table of contents on their own. Of course, after I produced something that mostly worked, I was searching through Lektor's documentation to find the answer to something else, and discovered that Lektor also has an official plugin for created tables of contents, and it was much simpler and better-written than my hacked-together solution. Oops.

It wasn't wasted effort, though, since I ended up needing to write my own plugin after all -- or more specifically, modify the "table of contents" plugin. I want to write Markdown without worrying about what other HTML heading tags may already be present on the page, but I also don't want to have the headings inside a blog post display the same way that the title of the blog post displays. That means I needed a way to adjust the headings in the output, so that when a blog post would normally output a <h1> tag, it becomes a <h2> tag instead.

Lektor's plugin system can hook directly into the Markdown processing system, which is super useful for exactly this type of modification. However, each part of the Markdown processing system can be modified by only one plugin at a time, and the "table of contents" plugin was already modifying how Markdown output headings. (In order to have a correctly linked table of contents, the header tags need to have an ID attribute, so the links have something to target.) When I tried writing my own Lektor plugin to adjust the heading level, it wasn't able to run simultaneously with the "table of contents" plugin. Even worse, it was a silent failure: Python was simply overwriting one modification with another.

I ended up forking the table of contents plugin to add this feature to the plugin directly. It would be nice if one plugin could modify the output of another plugin, so that this sort of tight coupling between plugins was unnecessary.

Lektor Is Powerful

Despite the learning curve, I'm glad I chose to use Lektor for this project. Even though I probably won't use Lektor's admin interface very much, I'm sure I'll build other projects with Lektor that are used by non-technical editors. The combination of high-performance static files and easy editing capabilities is a powerful one, and one that I expect will make a big difference when companies select which technology they want to use for their website.

If you'd like me to teach you about Lektor, or build you a website with it, let me know!