Diagrams with

6. Jan 2021

I think it can be said that at VSHN we have a certain obsession with documentation. This goes beyond the requirements set by our customers, or by those imposed by certifications such as the ISO 27001 or ISAE-3402. We have found that as a team we can work better when we can refer to written documentation at all times.

In the past few years we have standardized our documentation toolkit: we have adopted Asciidoctor as the lingua franca for our documentation. We have put in production various documentation websites based on Antora: our Handbook, our Knowledge Base, and the Project Syn documentation are some examples.

That works great for text. But what about diagrams? Our documentation has lots of them, and although embedding PNG files works fine, it does not “scale” very well.

For that reason we have set up an instance of Kroki in production (in APPUiO, of course!), to enable the generation of SVG diagrams based on various formats: PlantUML for UML diagrams, Nwdiag for network diagrams, and Ditaa for simple box-and-arrow kind of diagrams, all produced and shown in a crisp and neat SVG format. We love Kroki! It is such an awesome idea, that it has even been integrated to GitLab as a supported diagramming tool. How cool is that? In general, the Asciidoctor ecosystem has very good integration of diagrams into workflows, and this extends to Antora as well.

I am not going to dive into the benefits of vector vs. raster images; I think the readers of this article are well aware of the bonuses the former has over the latter. SVG diagrams look great in both online and print, but they can be a bit complicated to draw by hand (duh!).

But here’s a confession: I’m not a big fan of editing text-based diagrams either. But that’s just a personal choice. And the truth is, many other non-technical VSHNeers find the whole “diagrams as text” thing a bit arcane.

So that means that we needed a more accessible tool for them. The ideal diagram drawing tool for VSHN must have the following requirements:

  • Cross-platform: Most of us at VSHN use Linux, but a sizable number also use Macs and Windows laptops.
  • Accessible to non-technical VSHNeers: Not everyone at VSHN is a DevOps engineer.
  • Simple to use: If possible, using a point-and-click interface; for example, in our Confluence wiki we have enabled the Gliffy extension, which allows non-technical users to create stunning diagrams.

So we started our search. Leaving aside tools like Inkscape, that are too generic, like Asciiflow, that are too limited, or like Dia, that are too platform-specific, it took us a while to find a tool that would fit our requirements. But we found it!

Please welcome (previously also known as It is a web application geared specifically to the generation of diagrams, very easy to use and ticking all the boxes that we needed.

And even better, there is a Visual Studio Code extension that allows to edit diagrams locally, directly on your laptop, in Linux, Mac and Windows.

How do we integrate this with Antora? Very simple. In the assets/images folder of our documentation components, create your diagrams using the *.drawio.svg extension. These are automatically associated by Visual Studio Code with the extension, and provides a live editor with all the bells and whistles you might expect.

And then, well, just image::diagram.drawio.svg[] in your documents, git commit and push.

This approach is definitely more accessible to non-technical VSHNeers, making it super easy to edit diagrams online, or locally in Visual Studio Code.

To finish, here’s a Pro Tip™®©: switch the extension to the “Atlas” theme, since some lines in the extension lack contrast, and aren’t easily seen when using a dark theme. You can change the extension theme with the selector at the bottom right of the screen.

PS: there is an open issue in Kroki to add support for diagrams. Can’t wait to see it in action!

Christian Сremer

Christian Cremer ist ein DevOps-Ingenieur bei VSHN.

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