Merge pull request #641 from darkdoc/uninstall_blogpost

feat: Add pattern uninstall blogpost

Author: mbaldessari

content/blog/2026-02-16-pattern-uninstall.adoc

@@ -0,0 +1,91 @@
+---
+ date: 2026-02-16
+ title: Experimental support for pattern uninstall
+ summary: Uninstalling patterns now possible
+ author: Akos Eros
+ blog_tags:
+ - patterns
+ - announce
+---
+:toc:
+:imagesdir: /images
+
+We are excited to announce that uninstalling patterns are now experimentally supported from pattern operator version 0.0.65
+To initiate the uninstallation, only the pattern cr needs to be deleted. 
+[source,bash]
+----
+oc delete -n openshift-operators patterns/<pattern-name>
+----
+
+== Initial approach
+
+When we initialy started to work on supporting pattern uninstall, the naive approach was to remove the app of apps, and let argocd handle and clean up the rest.
+Unfortunatelly this path was unfeasable for two reasons: some long outstanding issues in argocd regarding application health checks,
+link:https://github.com/argoproj/argo-cd/issues/6708[**here**] and link:https://github.com/argoproj/argo-cd/issues/10550[**here**]
+and the hub-spoke architecture with acm policies.
+
+
+== Gory implementation details
+
+We decided to go with a more fine grained solution, and do phases:
+
+* Delete spoke child applications
+* Delete spoke app of apps
+* Delete hub child applications
+* Delete hub app of apps
+
+The main control is in the operator, we pass the phase as a variable to clustergroup chart, and to the acm chart.
+In order to achive this, we made some changes to the clustergroup chart, to remove child applications when needed. 
+In the acm chart we also needed some changes to support distinction between the phases in hub and spoke clusters.
+The resource removal is still managed by argocd.
+In prior operator versions the gitops subscription was owned by the pattern CR, we transfer the ownership to the patterns operator.
+The patterns operator, and cluster-wide OpenShift GitOps instance will remain installed.
+
+To initiate the uninstallation, only the pattern cr needs to be deleted. 
+[source,bash]
+----
+oc delete -n openshift-operators patterns/<pattern-name>
+----
+
+=== Deletion Phase Flow
+
+We store each phase in the pattern status deletionPhase, initialized as empty string.
+
+==== Initial Phase
+
+Right after deleting the pattern cr we set the deletionPhase to DeleteSpokeChildApps if we have acm hub resource or DeleteHubChildApps if we have no acm hub detected.
+
+==== DeleteSpokeChildApps
+
+When deleting spoke apps we update the clustergroup chart global.deletePattern variable to DeleteSpokeChildApps, this gets passed to the acm chart.
+The acm chart passes/changes global.deletePattern variable to DeleteChildApps, so the spoke clustergroup chart can start to remove child applications.
+
+We check the spoke child applications from the operator, and once all are gone, we change the deletionPhase to DeleteSpoke.
+
+==== DeleteSpoke
+
+This will be passed through the clustergroup chart to acm where the application policy will be deleted, and because pruneObjectBehavior: DeleteIfCreated is set, the app of apps will be removed from the spoke(s).
+
+We check the spoke app of apps from the operator, and once it is gone, we change the deletionPhase to DeleteHubChildApps.
+
+==== DeleteHubChildApps
+
+At this phase we detach all managed clusters from the hub cluster.
+We update the clustergroup chart global.deletePattern variable to DeleteChildApps so argocd can start to remove child apps from the hub.
+
+We check the hub child applications from the operator, and once all are gone, we change the deletionPhase to DeleteHub.
+
+==== DeleteHub
+
+The last phase we remove the app of apps from the spoke, which will remove all the subscriptions and namespaces, and remove the pattern cr as well.
+
+
+== Known limitations
+
+We did our due diligence and tested the uninstallation of the mcg pattern with both hub and spoke clusters.
+____
+"By design, when OLM uninstalls an operator it does not remove any of the operator’s owned CRDs, APIServices, or CRs in order to prevent data loss."
+____
+With the above in mind, we only remove operators/subscriptions, and do not remove any crds.
+If the operator is installed to a namespace, its ClusterServiceVersion will be removed (when the namespace is deleted).
+However if its installed to a namespace that is not cleaned up (ie: openshift-operators) the csv will remain in the cluster.