You are reading our blog series: Aegir5 Roadmapping
In our previous post, we looked at the Tasks and Operations which form the building blocks for the user interface in Aegir5. Here we’ll look at the additional entities required to support the Kubernetes-based backend framework.
It is worth noting that Aegir has always had a tension between Developer and SysAdmin use-cases. We’ll cover this in more depth in a later post. For the moment, we’re focused on the Developer use-case.
One thing to bear in mind is that Kubernetes operates quite differently than configuring and operating Nginx and MySQL directly, as we do with Aegir 3 Provision. As a result, the types of entities we are working with are going to be somewhat different. However, they will largely map to existing concepts in Aegir 3.
As seen in the diagram from the Kubernetes backend post (reproduced below), the core entities are dealing with are Clusters, Projects, Releases and Environments that we’re managing.
N.B. The terms below are how we’re currently describing the high-level components. Our goal here is to make these as natural and clear as possible. This may evolve over time, especially if we have to continuously explain what any of them mean (i.e. “Platform”).
Clusters, in this case, map fairly well to Servers. We intend to support provisioning of Clusters in the future. For the time-being, we will simply be pointing at existing Clusters to which we will want to deploy our applications.
Projects represent the codebase at a more abstract level. Whereas Releases (see below) are fully instantiated codebases, Projects represent the source of the codebase itself; usually a Git repository.
We may introduce a similar entity type, Applications, down the road. These would serve a similar purpose, but optimized for “cattle” in the SysAdmin use-case.
Releases are basically the equivalent of Platforms in Aegir 3. They capture the runtime environment, with a specific version of our codebase deployed and all dependencies downloaded. In Kubernetes, these are basically container images.
Sharing a common codebase across multiple sites can be achieved by leveraging the same Release. However, unlike Platforms, we are not intending to support Drupal’s multisite capability in Aegir5.
Multisite adds a lot of complexity, especially when running in a containerized environment. It also introduces multiple security and stability concerns.
Environments become the equivalent of Sites in Aegir 3. They capture the specific configuration required to run an instance of a specific Release of the Project (or Application), along with the storage required for both the database and any uploaded files.
These are what we believe to be the basic building blocks that we need to wire up to the Drumkit Kubernetes backend. We’ve tried not to bake in too tight of a coupling to the Kubernetes backend. They ought to be re-usable for the Ansible backend, as well.
Our medium-term goal is to build a robust, reliable and flexible continuous delivery system. Some of this will likely require much more opinionated approaches. We want to keep the basic components minimally opinionated, so that they can be composed into more elaborate workflows to satisfy different use-cases (eg. SaaS operations).
So far in this series we’ve looked at the Kubernetes framework we’ve built which will form the new backend for Aegir5. We’ve also explored the Drupal content architecture that forms the front-end. In the next post we’ll look at the Queue architecture which ties the front-end and back-end together before moving on to our Roadmap for bringing the whole thing together.
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