determine-promotion-needs.md

Determine whether a promotion is needed

This document looks in a bit more detail to the part of the solution around detecting or notifying deployment changes. It is the part of the promotions solution described in the diagram.

   sequenceDiagram
    participant pc as Pipeline Controller (Managment)
    pc->>pc: authz and validate event
    participant k8s as Kubernetes Api
    pc->>k8s: get pipeline
    pc->>pc: promotion business logic

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The responsibility of the pipeline controller is to determine whether, at the back of the deployment event and a pipeline definition, a promotion is required and initialise the promotion.

Input for promotions decisions

The following input elements are required:

1. Context around the last deployment which comes from the deployment event.
2. The set of pipeline spec.environments which is defined in the pipeline spec.

At the back of the following pipeline

apiVersion: pipelines.weave.works/v1alpha1
kind: Pipeline
metadata:
  name: podinfo
  namespace: default
spec:
  appRef:
    apiVersion: helm.toolkit.fluxcd.io/v2beta1
    kind: HelmRelease
    name: podinfo
  promotion:
    pullRequest:
       url: https://github.com/organisation/gitops-configuration-monorepo.git
       branch: main
  environments:
  - name: dev
     targets:
     - namespace: podinfo
        clusterRef:
          kind: GitopsCluster
          name: dev
  - name: qa
      targets:
          - namespace: podinfo
            clusterRef:
              kind: GitopsCluster
              name: qa
          - namespace: podinfo
            clusterRef:
              kind: GitopsCluster
               name: perf
  - name: prod
      targets:
        - namespace: podinfo
          clusterRef:
            kind: GitopsCluster
            name: prod

Promotion decisions business logic

Given the previous input, the following requirements will be met for promotions.

1. Promotion tasks are applied to deployment targets.

For example, given the previous example, when a deployment to dev deployment cluster has been received, a promotion for environment qa will start by executing the promotion strategy pullRequest to the two deployment targets qa and perf

2. Promotion between environment will happen when at least one of lower-environment deployment targets has been successfully deployed.

In the previous example, it means that we just need to wait for either qa or perf deployment targets has been successfully deployed (event has been received), in order to start the promotion from environments qa to prod.

3. Promotions will happen for all the environments but the last one.

Once a deployment event for prod has been received, no further promotions will be executed.

Once determined the need, the promotion strategy to use is specified in the promotion field.

Once a promotion is required, next is to execute. More information about promotion strategies could be found in here