werf new feature: deploy dependency order (v2.2.0+)

[shurup]

Briefly

The new werf.io/deploy-dependency-<name> annotation brings more flexibility in specifying the order in which Kubernetes resources are deployed.

This feature became available starting from werf v2.2.0, which is currently in the Alpha release channel.

Background & details

werf.io/deploy-dependency-<name> is an alternative for werf.io/weight, init containers, as well as other methods of reordering resource deployment. This annotation expresses the dependency between the resources.

Example:

kind: StatefulSet
metadata:
  name: postgres
---
kind: Deployment
metadata:
  name: backend
  annotations:
    werf.io/deploy-dependency-1: kind=StatefulSet, name=postgres, state=ready

Brief comparison with other methods:

• Unlike werf.io/weight, you do not have to split the resources into consecutive deployment groups: the resource deployment will commence as soon as its dependencies are satisfied, so there's no need to wait for other things. This approach is faster and allows you to implement scenarios that cannot be done with werf.io/weight. You may also wait for the resource to be present (state=present) rather than ready.
• Unlike Kubernetes init containers, you don't need to write massive shell scripts. On top of that, this annotation works for any resources, not just for controllers and pods.

Like a Swiss knife, this annotation will "replace" hooks, weights, external dependencies, etc. (Technically, they will still be there since we’ll preserve compatibility.)

This feature has a lot more planned: an external option for out-of-release resources, state=absent for dependency on resources being absent, regular expressions for kinds, names, and others, as well as an option to filter by the chart name.

Note: Previously, this annotation used to be called <name>.dependency.werf.io. You may have heard of it at our presentations. dependency.werf.io is now considered deprecated in favour of werf.io/deploy-dependency.

Additional details

• Resource dependencies in the Deploy annotations documentation;
• Deployment order in the Deploy documentation section.