This is an article in a series on Deployment.

Docker has popularised the concept of deploying containers. Containers should not be confused with images. VPS providers for example, run images in a virtual machine, on a much larger physical machine. Before Docker, when you would like to have some form of reproducible builds, you would build your own images to create controlled environments. These images were then spun up like virtual machines. Docker, however, is building on Linux kernel features such as namespaces and cgroups, hence not requiring a full OS as a lot of tasks are executed by the host-kernel, outside Docker, making it a more efficient way of deploying. Security wise, one might argue that hardware based virtualisation is safer, but when you’re controlling the machine something of reduced importance.

There are different ways to run containers: Docker, Podman, Kubernetes and more. You may even consider running containers using …

Kamal was introduced in 2023 (back then as MRSK) as an alternative way to deploy and manage containers on a server. It is marketed as Capistrano for containers, and as a big fan of the simplicity of Capistrano I was intrigued. I despise the political ideas of one of Kamal’s creators, but I think on the tech/implementation side he is promoting solutions that I honestly think are good (including HTML over the wire). Kamal is ‘simply’ some tooling around running images using Docker on a server, with zero-downtime deployments.

Some preparation

This is how I prepared for my testing:

1. I had to set up an SMTP server as my sendmail solution (that actually worked quite well for my smallish projects, no need for sendgrid or the like); see my post on getting Chasquid up and running on Debian.
2. I installed docker from the Debian repo’s (and not Docker’s), so it is automatical…

This is the start of a series on deployment

In the old days web software was deployed by uploading software via FTP, in a folder that was then read by a web server, and then presented to the user of the web-application. I’ve also deployed compiled .war files manually via a tomcat web-interface. Databases, storage, these were all pretty much managed by hand, sometimes even requiring physically adding a new drive or server rack.

The problem with this approach, though conceptually simple, is that deploying manually is error prone. One forgets about files, configurations, put files in the wrong directory, or forget to make changes to the database in order to make the latest change work.

The first step is hence automation of the manual steps. I will discuss a few high level dimensions that can be used to discuss solutions. I’d like to stress these are in practice scales and approaches can be mixed.

Style: Imperative vs declarative deployment…

I recently shared an overview article about Stubbing External Services in Rails. I found it when looking for the best way to stub a pletora of services in a microservices environment. Sure, docker (or whatever) everything and run it locally / in your test suite. But unless you’ve plenty of disk- and memory space, this isn’t always a viable option. The alternative: simulate the service. Mock or stub the endpoint.

VCR and Webmock

The go to gems are Webmock, which catches request and allows you to define the responses explicitly and VCR, which allows you to record responses, and play back.

VCR is quite cool, but as it is a recorder of earlier responses, there may be a lot of noise to dig trough when trying to make the responses a bit more generic (dealing with random token requests and what else)

For testing I pers…

1. Update eerst naar de laatste versie van ’t OS, Mojave. Je kunt deze gratis downloaden in de App store, zie upgrade instructies voor Mojave.
2. Installeer homebrew … macOS Terminal (zeg maar de Command Prompt van de Mac) vind je door Cmd+Spatie in te drukken en vervolgens “Terminal” te zoeken (meestal vind je die al na de eerste paar letters). Vervolgens de regel invoeren (kopiëren & plakken) die de website vermeld. Soms moet je extra dingen installeren; het script zal je daar doorheen leiden. Overigens, dat commando, Cmd+Spatie, opent wat Spotlight heet, ik vind dat de gemakkelijkste manier om programma’s te starten.
3. Install Docker for mac (je hebt hier tegenwoordig helaas een account bij DockerHub voor nodig). Dit download een DiskImage, sleep het programma naar de programma’s map (zoals het image waarschijnlijk ook al aangeeft in de achterg…

I haven’t had much need for isolating services, something that Docker is really good at. Most dependencies of my Rails apps are covered by Gemfile anyway (and packages.json for JavaScript) and reasonably isolated with rbenv. I don’t experience version related issues very often, as I try to stay reasonably up to date and not rely too much on the very state of the art. For temporary projects, however, Docker is a great solution, even for me :o I don’t want an entire JBoss suite running on my machine, so when I had to develop a Keycloak template I knew that Docker would be the right tool. While I’m going to discuss the specifics of getting started with a Keycloak image, the workflow described is replaceable by any other.

So what about Keycloak? Keycloak is a role based authorization and authentication tool …