chore: push prelimenary Upgrade docs for 2.20

docs/Upgrade-2.20.md

@@ -0,0 +1,72 @@
+# Upgrade to KubeZero V2.20 / Kubernetes 1.20
+
+# CloudBender
+## Changes
+- controller node names are now strictly tight to the AZ they are in: AZ1 -> controller00, AZ2 -> controller01 etc. to prevent controller03 from happening in case AWS launches new instances before the old ones are actually terminated 
+ 
+## Upgrade
+- Set Kubernetes version in the controller config to eg. `1.20`  
+- Update controller and worker stacks with latest CFN code
+
+- Upgrade requires careful replacement in case existing control planes are shuffled otherwise: ( this might reduce the number of online controllers temporarily to 1 ! )
+  - manually set controller ASG to Min/Maz 0 for the ASG currently hosting controller00
+  - terminate controller node in AZ1 which will return as controller00
+  - replace controller01 and 02 in similar fashion
+
+- replace worker nodes in a rolling fashion via. drain / terminate / rinse-repeat
+
+# KubeZero
+
+## New features
+
+### NATS
+Deploy NATS services
+
+### TimeCapsule
+Providing backup solutions for KubeZero clusters:
+  
+- scheduled snapshots for EBS backed PVCs incl. custome retention and restore
+
+
+## Changes
+
+### General
+- various version bumps
+- removed deprecated nodeLabels from `failure-domain.beta.kubernetes.io/[region|zone]` to `topology.kubernetes.io/[region|zone]` please adapt existing affinity rules !
+
+### Istio
+- hardened and optimized settings for Envoy gateway proxies
+- improved deployment strategy to reduce errors during upgrades
+- Added various Grafana Dashboards
+
+## Metrics
+- Added various dashboards for KubeZero modules
+- Updated / improved dashboard organization incl. folders and tags
+- Grafana Dashboards are now all provided via configmaps, no more storing of state required
+- Custom dashboards can easily be provided by simple installing a ConfigMap along with workloads in any namespace
+
+
+
+## Upgrade - Without ArgoCD
+1. Update CRDs of all enabled components:  
+  `./bootstrap.sh crds all clusters/$CLUSTER`
+
+2. Prepare upgrade
+Remove legacy monitoring configmaps
+`kubectl delete cm -n monitoring -l grafana_dashboard=1`
+Remove previous Grafana stateful config
+`kubectl delete pvc metrics-grafana -n monitoring`
+
+3. Upgrade all components  
+`./bootstrap.sh deploy all clusters/$CLUSTER`
+
+## Upgrade - ArgoCD
+- ArgoCD itself: `./bootstrap.sh deploy argocd clusters/$CLUSTER`
+- push latest cluster config to your git repo
+- trigger sync in ArgoCD incl. *prune* starting with the KubeZero root app  
+( only if auto-sync is not enabled )
+
+## Verification / Tests
+- check if all pods are RUNNING
+- check any Ingress services
+- ...